Nace CP 1 Course Manual

Cathodic protection tester

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CP 1–Cathodic

Protection Tester

Course Manual

February 2005

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Page 2 Acknowledgements The time and expertise of a many members of NACE International have gone into the development of this course. Their dedication and efforts are greatly appreciated by the authors of this course and by those who have assisted in making this work possible.
Page 3 IMPORTANT NOTICE: Neither the NACE International, its officers, directors, nor members thereof accept any responsibility for the use of the methods and materials discussed herein. No authorization is implied concerning the use of patented or copyrighted material. The information is advisory only and the use of the materials and methods is solely at the risk of the user.
Page 4: Table Of Contents
1:18 Direct Current (DC)......................1:18 Alternating Current (AC)....................Meter Operation ..................1:21 1:21 General ..........................1:22 Analog Meters ......................... 1:25 Digital Meters........................Exercise 1.1: Ohm’s Law................. 1:26 CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 5: Table Of Contents
Experiment 2.3 Current Direction in the Electrolyte in Corrosion Cells ......Chapter 2 Appendices Appendix 1–Reference Cell Maintenance Appendix 2–Conversions and Definitions Appendix 3–Customary Metric Conversions for Units Commonly Used in Corrosion-related Literature CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 6: Table Of Contents
Other International Standards ..................Experiment 3-1–Demonstrate the Use of Cathodic Protection to Mitigate Local Action 3:11 Cell Corrosion ......................... 3:25 Experiment 3-2–Demonstrate Change in Polarized Potential with Time ......CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 7: Table Of Contents
Testing Resistance Between a Pipe and Casing............... 5:26 Measuring Structure Continuity ..................Diode Bias....................5:27 Measuring Electrolyte Resistivity............. 5:28 5:28 Wenner Four-Pin Method ....................5:30 Soil Box ........................... CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 8: Table Of Contents
Monitoring Cathodic Protection ..............7:2 Recordkeeping .................... 7:4 Importance of Good Record Keeping ............7:4 Technical ........................... Legal..........................Data Sheets....................7:4 Date, Time, and Weather ....................Sketches..........................CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 9: Table Of Contents
Installation of Rectifiers or Other Power Sources ........8:29 General...................... 8:29 Rectifiers ....................8:29 DC Output....................8:30 Section 9 Chapter 9–Troubleshooting Introduction....................9:1 Electrical Isolation ..................9:1 General ..........................Testing a Pipeline ......................Casing Shorts........................CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 10 RP0193 “External Cathodic Protection of On-Grade Metallic Storage Tank Bottoms” RP0196 “Galvanic Anode Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks” RP0290 “Cathodic Protection of Reinforcing Steel in Atmospherically Exposed Structures” CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 11 Underground or Submerged Metallic Piping Systems” TM0101 “Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Storage Tanks” Section 11 Worksheets CP Tester Practical Exam Reference Sheet CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 12 EXAMINATION RESULTS NACE strives to mail out student grade letters within 4 to 6 weeks after the conclusion of each course. Examination results are not available via telephone. Information regarding the current status of grade letters for your course will be available on the web within 2 to 4 weeks after the course ends.
Page 13 You can detach the information below to keep for your record. To access your grades on the NACE Website go to: www.nace.org then click on Education/Certification then click on Student Grades STUDENT ID...
Page 14 It facilitates communications among professionals who work in all facets of corrosion prevention and control. If you subscribe to the NACE Corrosion Network, you will be part of an E-mail- driven open discussion forum on topics A-Z in the corrosion industry. Got a question? Just ask.
Page 15 Outdoor Field Program (weather permitting) DAY FIVE Chapter 8 Installing CP Components Chapter 9 Troubleshooting Indoor Field Measurement Test Station Practice Course Review DAY SIX Written and Practical Examinations CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 16 In this course we will study electrochemical corrosion because it is the most common form of corrosion that you will encounter. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 17 The field training activity is designed to simulate actual field conditions that students may encounter on-the-job. Students will perform tests and collect data. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 18 Certification Application A certification application must be completed and returned to NACE at the time of the written final examination. Successful completion of both the written and practical examination and submission of the CP 1–Cathodic Protection Tester certification application is required before certification will be issued.
Page 19 4. I understand that the registration number and/or category title may be used only by Certified Cathodic Protection persons (persons who have successfully completed CP 1, CP 2, CP 3 or CP 4). I understand that this applies to business cards, stationery, advertisements, etc. I understand that in no case may the NACE International logo, NACE International Cathodic Protection logo, or other NACE insignia be used.
Page 20 Instructions: Make and use as many copies of this form as needed. Please provide all information requested. Forms must be printed legibly in black ink or typed. Illegible information can delay the application process. For assistance with this form, contact the Education Division at NACE International Headquarters. Applicant Information: Name: A.
Page 21 Instructions: Make and use as many copies of this form as needed. Please provide all information requested. Forms must be printed legibly in black ink or typed. Illegible information can delay the application process. For assistance with this form, contact the Education Division at NACE International Headquarters. Applicant Information:...
Page 22 Please provide the information requested per the directions and definitions provided. ____________________________________________________________________________________ Job Information Applicant’s Name: ________________________ Who can NACE contact to verify this experience Job Title: _______________________________ Name: _________________________________ Company: ______________________________ Company: ______________________________...
Page 23 (7) Agree to inform clients or employers of any business affiliations, interests, and/or connections which might influence my judgment. (8) Agree to uphold, foster and contribute to the achievement of the objectives of NACE International. I understand that my failure to comply with these requirements could result in disciplinary action.
Page 24: Introduction
1,000 Volts 1 kilovolt 1.000 Volt 1000 millivolts 0.100 Volt 100 millivolts 0.010 Volt 10 millivolts 0.001 Volt 1 millivolt 0.000001 Volt 1 microvolt CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 25: Current
Direct current flows constantly in one direction in a circuit. Alternating current regularly reverses direction of flow, commonly 100 or 120 times per second. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 26: Resistance And Resistivity
If the resistivity of a material is known (see Table 1.1), the resistance of a conductor such as a cable or pipeline of known length and cross- sectional area can be calculated from: ρ × CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 27 • Large area of current flow Resistance will be greatest for: • High-resistivity (low-conductivity) media • Long path length for current flow • Small cross-sectional area of current flow CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 28 Measurement of electrolyte resistivity is covered in Chapter CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 29: Electrical Schematic Diagram Symbols
Basic Electricity Electrical Schematic Diagram Symbols Resistor Ground Battery Connection Rectifier Switch Diode CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 30: Electric Circuit
Ohm. Ohm’s Law can be expressed as follows: where E or V = Voltage (electromotive force) = Current (amperes) = Resistance (Ohms) E or V = IR = E/R = E/I CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 31 Ohms. Amperes and millivolts or volts and milliamps cannot be mixed. Consider the circuit in Figure 1.3. A battery is connected across a known resistance. E=1 volt − R=1000 Ohms Figure 1.3 Current Through a Resistor CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 32: Power
P = EI P = I where: P = Power in watts R = Resistance in Ohms E = Voltage in volts I = Current in amperes CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 33: Kirchhoff's Laws
This law states that as much current flows away from a point as flows toward it. It is especially useful in analyzing parallel circuits and in tracing current flow in complex piping networks. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 34: Series Circuit
(a series circuit), the higher the resistance and the lower the current for a given voltage. The resistance between a single galvanic anode and a structure also represents a series circuit. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 35 = 1 A Total IR Drop = 10 V = 1 A x 10 Ω = 10 V = 10 V Note that Kirchhoff’s Voltage Law is fulfilled. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 36: Parallel Circuit
• Total (equivalent) resistance is equal to the reciprocal of the sum of the reciprocals of the individual resistances. • The total (equivalent) resistance is always less than the smallest resistance in the circuit. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 37 = 20 V/4 Ω = 5 A = 20 V I = 20 V/2 Ω = 10 A = 20 V I = 4 A + 5 A + 10 A= 19 A CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 38: Series-Parallel Circuit
This is important in the design of cathodic protection. The cable running out to the groundbed represents a series circuit, the groundbed itself a parallel circuit. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 39 Figure 1.7: Ω Ω Ω Ω We now have an equivalent series circuit of two resistors, 1.05 Ω and 0.95 Ω for a total resistance of 2.00 Ω. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 40 = 10.5 V/2 Ω = 5.25 A = 9.98 A Note that Kirchhoff’s Current Law is fulfilled also. The currents entering Points A, B, and C equal those leaving these points. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 41: Direct Current (Dc)
50 hz or 60 hz current. Figure 1.11 shows a typical alternating current. Half Cycle Half Cycle Zero Current Zero Current Half Cycle Half Cycle Maximum Reverse Current Maximum Reverse Current Figure 1.11 Typical Alternating Current CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 42 There are two sets of windings on the core, the primary and the secondary. The primary winding is connected to the voltage source. The secondary winding is connected to the unit to which voltage is to be supplied. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 43 Impedance is the total opposition that a circuit presents to alternating current, similar to resistance in a direct current circuit. Impedance is equal to a complex ratio of AC voltage to AC current. Impedance CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 44: Meter Operation
(electronic amplifiers driving an electromechanical coil) are sometimes referred to as electronic meters (see Figure 1.14). METER ELECTROMECHANICAL ELECTRONIC MOVEMENT CIRCUITRY ANALOG DIGITAL ANALOG DISPLAY DISPLAY DISPLAY Figure 1.14 Meter Operation CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 45: Analog Meters
5. The reading on the scale represents the current flow through the coil from the external circuit. Note that the energy needed to operate the meter comes from the circuit itself. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 46 Also, when using an analog meter, the reference electrode is connected to the positive terminal to obtain an upscale reading. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 47 There are two reasons for this. First, when two structures are electrically isolated from each other by a fitting, there is a parallel resistance through the electrolyte. The ohmmeter cannot CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 48: Digital Meters
Also, when using a digital meter, the reference electrode is connected to the negative terminal to obtain the proper polarity reading. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 49: Exercise 1.1: Ohm's Law
The driving voltage between the anodes and the structure of a cathodic protection system is 1 volt and the protective current is 100 mA.. What is the circuit resistance? _______________________ CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 50: Exercise 1.2: Series Circuit
? ____________________ Calculate the sum of the voltage drops? _____________________ Does the voltage drop sum = total power voltage? Y N Is Kirchhoff’s Voltage Law fulfilled? Y CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 51: Exercise 1.3: Parallel Circuit
Calculate total current? ____________________________ Calculate total resistance using Ohm’s Law? ________________________ Calculate total resistance using the parallel circuit total resistance equation?____________________________ Using arrows, show the application of Kirchhoff’s Current Law. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 52: Exercise 1.4: Resistor And Instrument Lab
100 Ω 100 Ω 10 kΩ 100 Ω 100 Ω 100 Ω 100 Ω 100 Ω 100 Ω 100 Ω 10 Ω 100 Ω Diode 1,000 Ω CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 53 Does this sum equal the total measured voltage? DIODE CHECK Check the diode with the diode checking circuit. Is it functioning properly? CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 54 STEP 4 Measured Total Resistance R = ____________ Ω STEP 5 Calculated Current (I ) = E = : __________________ A STEP 6 Measured Current (I __________________ A CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 55 Calculated Total V = : ______________ V Measured Source Voltage (E ) : ______________ Volts DIODE CHECK FORWARD READING REVERSE READING ____________ _____________ Good ____________ ____________ ____________ ____________ Shorted CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 56 “Bad Fuse” “Good Fuse” 3. Replace the fuse with the proper rating. Replace meter cover. Check for proper operation as described above. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 57 C = Orange = 1,000 B = Blue = 6 D = Silver = ± 10% Resistance Value = 26,000 Ω ± 10%, or between 23,4000 Ω and 28,600 Ω CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 58: Basic Chemistry
CHAPTER 2 BASIC CHEMISTRY AND BASIC CORROSION THEORY Basic Chemistry Corrosion is defined by NACE International as the deterioration of a material, usually a metal that results from a reaction with its environment. Understanding corrosion and cathodic protection requires a basic knowledge of chemistry and electrochemistry.
Page 59: Compounds (Molecules)
It is this chemical bonding that defines many of the properties of a substance. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 60: Acidity And Alkalinity (Ph)
The pH scale is illustrated in Figure 2.3. The neutral point is 7. Acid solutions have a pH below 7 and alkaline, or basic, solutions have a pH CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000...
Page 61 Metals that corrode under low and high pH levels are termed amphoteric metals. Figure 2.4 illustrates this phenomenon. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 62: Basic Electrochemistry
Corrosion and cathodic protection pertain to the branch of electrochemistry concerned with charge transfer in aqueous or other liquid environments. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 63: Oxidation And Reduction
Figure 2.5 Anodic Process (half reaction) The electrode or metallic site where oxidation occurs is called an anode. Note: The term oxidation is not necessarily associated with oxygen. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 64 → H The electrode or metallic site where reduction occurs is called a cathode. The process appears in Figure 2.6. CATHODE ELECTROLYTE Figure 2.6 Cathodic Process (half reaction) CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 65: Electrochemical Circuits
Cations are positively charged ions and anions are negatively charged ions). These ions are current-carrying charges. Therefore, electrolytes with higher ionization have greater conductivity. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 66: Corrosion Cell
Corrosion is the result of the oxidation reaction in a corrosion cell. Oxidation is the loss of electrons as shown in the following reaction: → M + ne where n is the number of electrons involved. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 67: Cathode Reactions
The anode and the cathode can be on different metals or on the same metal as shown in Figure 2.9. ANODIC ANODIC CATHODIC Figure 2.9 Typical Local Action Corrosion Cells on a Structure CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 68 Figure 2.10. Ions are relatively heavy and slow moving. Consequently, electrolytes have much higher resistivities than metals. This causes a phenomenon called polarization. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 69: Use Of Voltmeters
Current, I, of the external circuit does not flow through the voltmeter to complete the circuit, an indication the voltmeter is in parallel instead of in series with the circuit. All voltage measurements are made in parallel. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 70 When measuring the voltage difference of dissimilar metals, the sign is positive when the positive terminal of the voltmeter is connected to the more noble metal as shown in Figure 2.13. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 71 With a left hand zero instrument, you can still connect the reference electrode to the negative terminal, but it is CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 72: Reference Electrodes (Half-Cells)
The electrode is composed of a copper rod, immersed in a saturated solution of copper sulfate, held in a CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 73 Saturated Copper Window Sulfate Solution Porous Copper Plug Sulfate Crystals Figure 2.14 Copper-Copper Sulfate Reference Electrode in Contact with Earth Figure 2.15 Portable Copper-Copper Sulfate Reference Electrodes CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 74 The potential of a reference electrode in the sun can decrease from 10 to 50 mV versus an electrode kept in the dark. EXPERIMENT 2.1 and EXPERIMENT 2.2 CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 75: Driving Force For Corrosion
“Causes of Corrosion”. There must be a voltage difference between the anode and cathode of a corrosion cell for current to flow. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 76: Corrosion Rate
21.2 Copper 20.8 45.8 (Monovalent) Zinc 10.7 23.6 19.4 42.8 Lead 33.9 74.7 Based on Table 2, Chapter 2, Basic Course Manual, Appalachian Underground Corrosion Short Course. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 77: Polarization
Depolarization is a condition that counters the effects of polarization. Depolarizers include: • Dissolved oxygen • Microbiological activity • Water flow CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 78: Anode/Cathode Ratio
In underground corrosion, high moisture content is generally associated with increased corrosion rates. However, total immersion (saturated soil) is not necessarily the most aggressive situation. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 79 Highly alkaline environments, generally with a pH greater than 8, can cause accelerated corrosion on amphoteric metals such as aluminum and lead. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 80: Causes Of Corrosion
The series is shown in Table 2.2. The potentials shown are approximate since they vary somewhat depending on the environment. Potentials are shown vs. a copper-copper sulfate. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 81 This is a useful corrosion cell since the current produced can do work for us. Eventually the case will corrode through—we have all seen batteries in that condition. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 82 If parts of a structure are at different temperatures, the higher temperature area is usually the more active area and becomes the anode of the corrosion cell. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 83 The bacteria serve as an intermediary in this reaction. The presence of bacteria may significantly increase corrosion rates in environments that would otherwise be relatively benign. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 84: Experiment 2.1–Metal Electrode Potentials In Tap Water
7. Place the reference electrode near the steel and record the steel’s potential. 8. Place the reference electrode near the zinc and record the zinc’s potential. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 85 1. Magnesium is more electronegative than copper, steel, or zinc. 2. Zinc is more electronegative than steel or copper. 3. Steel is more electronegative than copper. 4. Copper is more electropositive than steel, zinc, or magnesium. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 86: Experiment 2.2–Corrosion-Cell
4. Connect the meter to the metal samples as indicated below. Results Meter Positive Meter Negative Anticipated Actual Potential Lead Lead Potential mV Copper Steel +400 Steel Copper –400 CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 87 2. Place reference electrode in the water at the copper/water interface. 3. Record the potential. 4. Repeat Steps B1 and B2 for the steel. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 88 Step C—Polarized Potential Measurement 10 Ω Reference Electrodes Copper Steel Sheet Sheet 1. Connect the steel to the copper through the 10-Ω resistor. 2. Repeat steps B1, B2 and B4. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 89 2. Record the voltage drop across the resistor and note polarity. 3. Evaluate the direction of the current. 4. Repeat steps D1 to D3 for the other metal configurations shown in the table below. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 90 Meter Negative Direction of Lead Lead Conventional Current Which metal in External Circuit is the anode? Copper Steel Steel Copper Zinc Steel Steel Zinc Copper Zinc Zinc Copper CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 91 Thus, an Fe/Fe electrode can be either an anode or a cathode, depending on the other electrode to which it is connected. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 92: Experiment 2.3 Current Direction In The Electrolyte In Corrosion Cells
4. Connect the meter to the zinc and to the reference electrode as indicated in the figure . 5. Record the electrode potential with the reference electrode in the two positions indicated in the figure. 6. Evaluate the direction of current. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 93 Conclusion 1. Conventional current in the electrolytic circuit is from the anode to the cathode. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 94 1. Remove the reference cell tip, rod and end cap, and properly dispose of the fluid contained in the cell. 2. With non-metallic abrasive material (sandpaper), clean copper rod to a bright and shiny condition. 3. Re-assemble rod and end cap. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 95 7. Shake cell several times to mix cell solution with copper sulfate crystals. 8. Maintain fluid so that 95% of the cell is fluid filled. 9. Maintain cell so that copper sulfate crystals are always visible in the solution. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 96 0.100 ohm = 100 milliohms 0.010 ohm 10 milliohms 0.001 ohm 1 milliohm 0.000001 ohm 1 micro-ohm 1 meter = 100 cm 1 meter = 1000 mm CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 97 Where ρ, resistivity in Ω-cm a, the spacing of the pins (feet) R, the resistance measured (Ω) ρ, resistivity (Ω-cm) Ohm’s Law E = IR I=E/R R=E/I CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 98 Chapter 2 Appendix 3 U.S. Customary/Metric Conversions CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 99: Materials Selection
This will ensure that the cathodic protection system performs as designed. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 100: Types Of Mill Applied Underground Coatings
-40°F to 140°F (–40°C to 60°C). Long-term (10 to 15 years) moisture absorption can be a problem with these coatings, so cathodic protection current requirements may increase over time. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 101: Girth Weld And Other Field Coatings
All coatings should be applied in accordance with the manufacturer’s requirements. Inspection Procedures Initial Inspection Surface preparation must be inspected to ensure adherence with the specifications. Environmental conditions such as temperature, humidity and CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 102: Electrical Isolation
Maintenance Inspections While detailed inspections need to be made by the proper level Certified NACE Coating Inspector, cathodic protection personnel may be called upon to make an inspection of exposed coating. This can be done visually, looking for signs of disbonding, damage, checking, cracking, chalking, and other deterioration.
Page 103: Inhibitors
Corrosion prevention is dependent on the concentration of the chemicals in the liquid, and regular testing and chemical control must be initiated. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 104: Cathodic Protection
Cathodic protection does not actually eliminate corrosion. Instead, it transfers it from the structure to be protected to the cathodic protection anode(s). The structure is now the cathode of an intentional corrosion cell. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 105: Definition
The flow of current in this circuit is adjusted to assure that the polarized potential is at least as active as the most active anode site on the structure. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 106: Structures That Can Be Cathodically Protected
There are two methods of providing cathodic protection current to a structure: • galvanic anode system • impressed current system. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 107: Galvanic Anode Systems
CURRENT ANODE Figure 3.3 Typical Galvanic Anode Cathodic Protection Anodes There are several metals commonly used as galvanic anodes: • aluminum • magnesium • zinc. EXPERIMENT 3.1 CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 108 Galvanic anodes can be an economical choice for a cathodic protection current source under such conditions. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 109: Component Parts Of Galvanic Systems
–1.55 V referenced to a copper-copper sulfate electrode. Magnesium is normally used in soils and fresh water. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 110 Anode efficiency is the ratio of metal consumed producing useful cathodic protection current to the total metal consumed. For magnesium, anode efficiency is generally about 50%. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 111: Specifications Of Galvanic Anode Systems
This is achieved by one of the following methods: • using insulated copper wire provided by the manufacturer and thermite welded or otherwise attached to the structure. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 112: Impressed Current Systems
Materials that have been used as impressed current anodes include: • Graphite (carbon) • High-silicon, chromium, cast iron • Platinum-coated titanium and niobium • Aluminum • Magnetite CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 113: Power Sources
• for underground storage tanks • for underwater components of off shore structures • for foundation piles and sheet piling, both underground and in the water. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 114: Limitations Of Impressed Current Systems
Regular silicon iron consists of a very hard matrix, which has graphite flakes at the grain boundaries. The graphite produces an inherent weakness in the alloy. Adding chromium ties up free graphite as carbides and strengthens the alloy. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 115 Mixed metal oxide anodes (also referred to as DSA for dimensionally stable anode) consist of electrocatalytic activated coatings on a titanium substrate. The metal oxide coating is highly conductive and demonstrates an extremely CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 116: Power Supply
It contains a step-down transformer, a means of adjusting the voltage, a rectifier to change AC to DC, and various controls and other components depending on its usage. Figure 3.5 shows a rectifier schematic. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 117 Solar panels generate DC by a photovoltaic action with sunlight. The panels are combined with storage batteries to provide power during hours of darkness and on cloudy days. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 118 The generators also charge storage batteries so as to provide constant cathodic protection current. Wind-Powered Generator Storage Batteries in Suitable Housing Groundbed Structure Figure 3.7 Wind Powered Generator Installation CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 119: Electrical Connections
Electrical Connections All electrical connections used in impressed current cathodic protection systems (except the active anode surfaces) must be completely sealed with dielectric insulating materials. EXPERIMENT 3.2 CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 120: Factors Influencing Operation Of Cathodic Protection
Sand and Gravel Porous soils permit rapid changes in moisture content. This may lead to cyclic wetting and drying of the soil, thus changing its resistivity. Such changes will CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 121: Temperature
Ship hulls are a good example of this phenomenon. At anchor, the current requirement for the hull is low. When under way, however, the current CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 122: Make Up Of The Electrolyte
Figure 3.8 illustrates the effect of a shorted casing. END SEAL VENT PIPE CASING PIPE LYING ON CASING DUE TO LACK OF INSULATING SPACERS Figure 3.8 Cathodic Shielding Due to a Shorted Casing CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 123: Criteria For Cathodic Protection
NACE International Recommended Criteria General There are several criteria recommended by NACE. These will be found in various recommended practices (RP). The following discussion covers various metals in different environments. Pertinent recommended practices are also cited. When referring to these recommended practices, be certain to obtain the latest revision (the year of revision follows the RP number).
Page 124 (current required to operate the meter) or stray currents can be significant, however. The measurement circuit current is small if the input resistance of the meter is large. This is one reason why CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 125 It is imperative that you know the criteria specified for the structures you are testing. As noted earlier, there is no single, universal criterion for cathodic protection. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 126 • A minimum of 100 millivolts of cathodic polarization between the structure surface and a stable reference electrode contacting the electrolyte. The formation or decay of polarization can be measured to satisfy this criterion. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 127 (becomes more positive) at least 100 mV, the criterion has been met. Likewise, if the “instant off” reading is at least 100mV more negative than the native reading, the criterion has been met. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 128 There are other criteria and reference electrodes covered in this standard along with a lengthy discussion of testing techniques. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 129 • A negative polarized potential of a least 850 mV relative to a saturated copper-copper sulfate reference electrode. • A minimum of 100 mV of polarization. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 130 Systems references CGA Recommended Practice OCC-1, For the Control of Corrosion on Buried or Submerged Metallic Piping Systems. The criteria are the same as in RP0169. CSA Standard Z169 covers cathodic protection of aluminum. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 131 • Part 1 – Pipe, Cables and Ducts • Part 2 – Compact Buried Structures • Part 3 – Fixed Immersed Structures Criteria for steel are the same as those in NACE standard RP0169. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000...
Page 132 Experiment to Demonstrate Mitigation of Local Action Cell Corrosion with Cathodic Protection Part A 1. Insert steel and copper sheet in side of tray and 1-1/2 inches of fresh tap water. 2. Follow the diagram below. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 133 14 mA 14 mA Corrosion Current Corrosion Current Conventional Current Conventional Current 5. Measure polarized potentials of steel and copper. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 134 10,000 O 10,000 O 1,000 O 1,000 O 100 O 100 O 10 O 10 O Part C 1. Repeat Part B using 100-ohm and 10-ohm resistors. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 135 100 ohms 10 ohms CONCLUSIONS 1. Corrosion current decreases as cathodic protection current increases. 2. Corrosion current decreases as polarized potential of cathode is made more electronegative. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 136 Part B 1. Re-measure the polarized potential of the structure at intervals until relatively stable. Part C Leave overnight. Measure pH. Disconnect anode and take depolarized readings. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 137 ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ CONCLUSIONS 1. Polarized potential of the structure shifts electronegatively with time. 2. Cathodic protection current decreases with time. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 138 Assessments (see list of hazards) Acceptable Risk Assessment Acceptable Acceptable Preventative Measures New Risk Acceptable Assessment Acceptable Start Project Risk changes Figure 4.1 Safety Analysis Prior to Commencing Project CP 1–Cathodic Protection Tester Course Manual © NACE International, 2000 12/01/04...
Page 139: Electrical
AC power lines. Electrical Equipment (Rectifiers) Electrical Equipment (Rectifier) Case Always assume that the electrical equipment or rectifier case may be poorly grounded and is inadvertently energized. This has happened! Before CP 1–Cathodic Protection Technician Course Manual © NACE International, 2000 12/01/04...
Page 140 L.P. Ferris, B.G. King, P.W. Spence, H.B. Williams, Effect of Electric Shock on the Heart, AIEE Trans., Vol. 55, pages 468-515 & 1263 May 1936 and IEEE Std 80. CP 1–Cathodic Protection Technician Course Manual © NACE International, 2000 12/01/04...
Page 141 • The equipment is not to be re-energized until it has been inspected to make certain it is safe and all locks have been removed by the owner of the lock. CP 1–Cathodic Protection Technician Course Manual © NACE International, 2000 12/01/04...
Page 142: Explosions Or Ignitions
If a combustible atmosphere is present, an explosion can occur. To avoid this CP 1–Cathodic Protection Technician Course Manual © NACE International, 2000 12/01/04...
Page 143: Cathodic Protection Surveyss
• Assume that the potential to be measured may be hazardous. Do not contact a measurement circuit until the potential is determined to be safe. • If AC may be present, measure AC voltage first. CP 1–Cathodic Protection Technician Course Manual © NACE International, 2000 12/01/04...
Page 144 NACE Standard RP0177, Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems, contains valuable AC safety information.
Page 145: Hazardous Material
Safety precautions are given in the NACE International slide show entitled “Some Safety Considerations During Construction Near Power Lines." Always measure the AC voltage-to-ground voltage first before the DC structure-to-electrolyte potential or before touching the structure when in the vicinity of a power line.
Page 146: Reaction Products
Other precautions not discussed above that must be considered include: • Wear protective eyewear, gloves, shoes and other clothing. • Avoid open flames. • Avoid causing electric sparks especially in areas that may contain a hydrocarbon. CP 1–Cathodic Protection Technician Course Manual © NACE International, 2000 12/01/04...
Page 147 Know the handling/storage procedures for chemicals or other hazardous materials or equipment. • Working at heights. • Animals, reptiles and insects • Vehicles: Drive defensively and be aware of hazard situations that could occur CP 1–Cathodic Protection Technician Course Manual © NACE International, 2000 12/01/04...
Page 148: Other Portable Reference Electrodes
Manganese Dioxide The manganese dioxide electrode is also used in reinforced concrete structures. Graphite Electrode Graphite is a pseudo-reference electrode that is sometimes used in reinforced concrete structures. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 149 A stationary copper-copper sulfate reference electrode is used for installation underground. These electrodes are used to reduce IR drop in potential measurements at inaccessible locations. Figure 5.1 shows a stationary CSE unit. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 150: Typical Applications
The most common DC voltage scales on meters and their usage are as follows: • 200 millivolts–Current shunt readings • 2 Volts–Structure-to-electrolyte potentials • 20 Volts–Structure-to-electrolyte potentials and rectifier voltage output CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 151 The operator records above grade appurtenances and other identifying items along the way so the location of the data can be CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 152 When testing multiple pipelines that are bonded together, the survey data may represent an average of all the pipelines. Voltmeter Reading Cu/Cu SO Ref. Cell Electrolyte Pipe Potential Profile Figure 5.2 Pipe-to-Soil Potential Profile CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 153 They are also used in stray current areas where voltages may fluctuate. The fluctuations are easily discernible on the chart. Recording voltmeters may display data on charts or may record data for later computer printout. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 154 Strip Chart Recorders Strip chart recorders contain a roll of chart paper. A pen or stylus records voltage as the chart moves. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 155: Measuring Current
A current measurement using an ammeter requires more caution than voltage because the circuit has to be broken. Power of the external circuit should be de-energized before breaking the circuit and inserting an CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 156 The most common DC current scales on meters are as follows: • 200 microamps • 2 milliamps • 20 milliamps • 200 milliamps • 2 amps • 10 amps CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 157: Shunts
In fact, current shunts are favored over using an ammeter in most cases. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 158 Calculate Current: 1. Convert units of voltage: 50 mV = .05 V 2. Calculate current using Ohm’s Law I = .05 V / .01 Ω = 5 A CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 159 Remember also that the voltmeter is connected in parallel with the shunt. Consequently, the direction of current flow through the meter will be the same as that through the shunt. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 160 Various types of shunts and their values are shown in Table 5.2. The shunt rating shown in the table is in amperes/millivolt. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 161 SW or CP .005 .0033 .0025 .002 .0017 .001 .0008 0.00067 .0005 J.B. Type Agra-Mesa Cott or MCM Red (MCM) Red (Cott) Yellow (MCM) Orange .001 (MCM) CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 162 With a shunt in place, the measurement can be made without having to open the circuit. This not only saves time, but also yields a more accurate reading than that obtained with an ammeter. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 163 • 2-wire test points • 4-wire test points Connections to the structure should be made by permanent test wires; probe rods are sometimes used on bare or poorly coated piping. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 164 For example, if the voltage drop across a 200-ft span of 30-in. (76.2 cm) pipe weighing 118.7 lbs./ft (176.65 kg/m) is 0.17 mV, then current flow is calculated as follows: CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 165 Should there be an odd-sized joint within the span, or some appurtenance such as a valve, the calculated resistance will not be correct. The 4-wire test method overcomes these difficulties. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 166 (7832 kg/m ) and steel resistivity of 18 microhm-cm. R = 16.061 x resistivity in microhm-cm = Resistance of 1 ft of Weight per foot pipe, microhms CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 167 2. Measure the voltage drop in millivolts across the measuring span (without the battery current) using the inside potential measurement leads. This voltage drop is due to normal pipeline current. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 168 Most digital meters will not read below 0.1 mV. If readings below 0.1 mV are anticipated, or if a zero reading is obtained during a test, a more sensitive meter must be used. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 169: Measuring Resistance
It will be used again in measuring resistance across an isolating fitting. Under this application, a known current and voltage are used and the resistance is calculated. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 170: Using An Ohmmeter
There are isolator checkers that are based on a high radio frequency and are more reliable for isolators in service. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 171: Electrical Continuity
Isolating fittings may also be used for stray current control. Isolation strategically placed in a piping network, for example, can increase the longitudinal resistance sufficiently to minimize the pick up of stray current. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 172: Isolation (Insulating) Joints
These include telemetering and other remote monitoring equipment, electrical valve operators, gauge lines, and the like. If these attachments bypass an isolating fitting, a short circuit will be created. You need to be CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 173: Testing Resistance Between A Pipe And Casing
If the casing has only one wire, the vent is used as the other one. Measuring Structure Continuity There are several ways to measure structure continuity. We will discuss only the fixed cell, moving ground method. In this test, one reference CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 174: Diode Bias
To correctly verify diode operation, at least one lead must be disconnected from the circuit. Diodes cannot be properly checked while in the circuit or with power on. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 175: Measuring Electrolyte Resistivity
The resistance, “R,” at each pin spacing “a”, is the resistance from ground level to a depth equal to the spacing of the pins. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 176 To ensure accuracy, it is good practice to take two sets of data, perpendicular to each other. This will help expose any anomalies in the soil layers. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 177: Soil Box
If a soil box and resistivity meter are available, take time now to work with them; connect the instruments as shown in Figure 5.14. Fill the soil box with water and any available soil samples. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 178: Resistivity Probe
Care must be taken when using these instruments not to break the electrode bulb. Soil pH may also be measured using an antimony electrode and a copper- copper sulfate electrode. The antimony electrode consists of a slug of CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 179: Use Of Pipe Locating Devices
There are two types of pipe locators. Some locators contain both types in one unit: • Conductive • Inductive. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 180: Conductive
Figure 5.16 illustrates the principle of the conductive locator. Transmitter Receiver Pipe Figure 5.16 Conductive Pipe Locator Principle Figure 5.17 shows an example of a conductive locator. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 181: Inductive
Figure 5.18 illustrates the principle of the inductive locator. Transmitter Receiver Pipe Figure 5.18 Inductive Pipe Locator Principle CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 182: Use Of Current Interrupters
CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 183 An instrument is used to measure corrosion rate electrically. If the protection is effective, the corrosion rate is zero. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 184: Definitions
Stray currents can be produced by any system conducting an electric current that has two or more points of contact with an electrolyte. These points of contact must have a voltage between them. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 185: Types Of Stray Current
Steady state or static stray currents maintain a constant magnitude and direction. Examples include cathodic protection interference and ground current from high voltage DC (HVDC) transmission line earth electrodes. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 186: Identification Of Stray Current
The presence of any of the sources listed above should lead you to suspect that you might encounter dynamic stray current. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 187: Steady State Stray Current
A data plot such as that shown in Figure 6.2 would indicate the presence of cathodic interference. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 188 If so, an interference problem may have been created somewhere on your structures. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 189: Stray Current Corrosion Control
Figure 6.3 shows the use of a mitigation bond to solve a stray current problem stemming from a rail transit system. Figure 6.4 illustrates a similar bond for mitigating cathodic interference. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 190 Current Flowing Through MITIGATION the Earth to Return to BOND Protected Line Protected Line Foreign or Affected Line Figure 6.4 Mitigation Bond Used to Solve a Cathodic Interference Problem CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 191: Mitigation With Cathodic Protection
Galvanic anodes may be used to overcome cathodic interference problems. Anodes are placed in the area of current discharge. The testing and design of such systems are, however, beyond the scope of this course. EXPERIMENT 6.1 CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 192: Experiment 6.1 — Demonstration Of Cathodic Interference
5. Measure and record potentials on the foreign structure at reference electrode positions D, E, and F. 6. Connect cathodic protection system. 7. Repeat Step 5. 8. Repeat Step 2. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 193 D. 3. The potentials on the cathodically protected structure are altered by the presence of the foreign structure because the current distribution has been disturbed. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 02/01/05...
Page 195: Monitoring Requirements
Monitoring Cathodic Protection Effectiveness and Recordkeeping Monitoring Requirements Although regulatory agencies have adopted standards set forth by NACE, International Standards Organization (ISO), Det Norske Veritas (DNV), etc. regarding corrosion control, many have gone a step further by specifying specific measurements and time intervals in which these measurements must by taken.
Page 196 • Coupon test stations • Electric resistance probe test stations • Structure examination by excavation or divers • Close interval potential surveys CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 197: Recordkeeping
Date, Time, and Weather Date, time, and weather conditions should always be noted on data sheets. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 198: Sketches
The same is true of many large industrial plants, refineries, college campuses, and similar facilities. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 199 Accuracy in your work documentation is just as important as accuracy in your data sheets, as discussed above under “Data Sheets.” CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 200: Test Stations
Major crossings between underground structures will generally warrant installation of a test station. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 201: Environmental Factors
Conductor connections at bonds to other structures or across isolating joints should be mechanically secure, electrically conductive, and suitably coated. Bond connections should be accessible for testing. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 202: Types Of Test Stations
Figure 8.1 or it may be flush mounted as illustrated in Figure 8.2 Test Box Test Wires Structure Figure 8.1 Typical Post Mounted Potential Measurement Test Station CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 203 The direction of current is determined by the polarity of the voltage. A typical IR drop station is shown in Figure 8.3. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 204 Sufficient inspection should be made to ensure that no metallic contacts exist or are likely to develop between the casing and carrier pipe. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 205 To determine what effects are occurring and to provide a facility to mitigate any undesirable effects, a foreign line test station is installed. See Figure 8.5. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 206 Flanges may be double insulated or single insulated. Figures 8.6 to 8.8 show the construction of a number of different types of pipe isolation joints. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 207 Installing C.P. Components ISOLATING UNION ARMORED GASKET INSULATING GASKET PIPE END SEPARATOR Figure 8.6 Isolating Coupling DI-ELECTRIC GASKET DI-ELECTRIC SPACER Figure 8.7 Isolating Union CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 208 Service conditions can vary greatly on different systems. In selecting an electrical isolating device, be certain that the materials of constructions meet the service requirements, both from the standpoint of temperature and mechanical properties. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 209: Coupons
“instant off” potential measurements without having to interrupt the cathodic protection rectifier. Another is to measure the protective current density on a holiday of known size. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 210 Figure 8.11 shows a coupon station. Current Interrupt Switch Shunt Reference Cell Reference Tube Pipe Lead Pipeline Coupon Element Figure 8.11 Typical Coupon Test Station CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 211: Wire Attachment
Figure 8.12. The mixture is ignited with a flint gun, melts, and drops down, welding the wire to the structure. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 212: Literature
There are welders for making connections to both horizontal and vertical surfaces. Be certain the mold and welding surface are thoroughly dry. Damp conditions will cause the molten metal to spatter, creating a safety hazard. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 213: Galvanic (Sacrificial) Anodes
It is important that galvanic anodes be installed according to construction specifications. Improperly installed anodes will very likely not function properly. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 214: Prepackaged Anodes
Lead wires should have sufficient slack in them to avoid strain. Typical prepackaged anode installations are shown in Figures 8.13 and 8.14. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 215 Insulated Lead Figure 8.13 Single Prepackaged Vertical Anode Insulated Connections Hole Depth Header Based Cable on Soil Resistivity Structure Anode Spacing Figure 8.14 Multiple Prepackaged Vertical Anodes CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 216: Non Packaged Anodes
Care should be taken to prevent damage to the coating when installing bracelet anodes. Be certain the anode pigtail is attached to the pipeline. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 217: Offshore Anodes
1,400 pounds each. The anodes are cast on a steel pipe core, which in turn is welded to the platform or other structure to be protected. Figure 8.17 shows a typical example. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 218: Impressed Current Groundbeds
Impressed current anodes may be installed in either surface groundbed configurations or a deep anode configuration. Installation techniques are discussed below. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 219: Handling And Inspection Of Anodes And Cable
Coke breeze backfill can be tamped around a bare anode or anodes may be purchased prepackaged in backfill as shown in Figure 8.18. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 220 If insulation integrity on the buried or submerged header cable (positive lead wire), including splices, is not maintained, the cable will fail from electrolytic corrosion. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 221: Surface Groundbed Configurations
A typical vertical anode installation is shown below in Figure 8.19. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 222 Again, be certain to follow the design drawings and specifications during the installation. Figure 8.20 illustrates a typical horizontal installation. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 223 This precaution is especially important with surface distributed anode systems where there may be an extensive amount of cable in the ground. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 224 A surface distributed groundbed is shown in Figure 8.22. Figure 8.23 illustrates a distributed impressed current bed protecting piling under a wharf. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 225: Deep Anode Groundbed Configuration
This is done by measuring the resistance between a metal bar or anode lowered down the hole and some low resistance ground. The log helps to determine the desired locations for the anodes. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 226 A cable is then run from the positive bus bar to the positive terminal in the rectifier. All deep anode groundbeds must be permitted, installed and completed in accordance with state and local codes. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 227: Negative Circuit
Negative cables may be fairly heavy, ranging typically from No. 6 AWG to No. 2/0 AWG or larger. This size wire is too large to connect to a pipeline CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000...
Page 228: Installation Of Rectifiers Or Other Power Sources
The transformer reduces incoming AC voltage down to the operating voltage of the cathodic protection system. The rectifier changes the incoming alternating current to direct current for cathodic protection. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 229: Dc Output
Follow all of the precautions mentioned previously under “Anode Circuit” with regard to proper connection and installation. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 230: Troubleshooting
This is illustrated in Figure 9.1. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 231: Testing A Pipeline
Current flow back to the main will be found on the shorted service line. See Figure 9.2. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 232 Figure 9.3 shows a typical situation. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 233: Casing Shorts
A current pick-up test is run by applying a cathodic protection current to the pipeline and measuring the resultant shift in pipe-to-soil potential. If the same potential shift occurs on the casing, a short exists. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 234 Remember, you cannot use an ohmmeter to test resistance between a pipe and casing. This was explained in Chapter 1, but is repeated here for emphasis. There are two reasons why an ohmmeter cannot be used. First, CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 235 Figure 9.5 illustrates resistance testing. 0.17 mV VOLTS Wires must be AMPS color Power Current coded Source Interrupter PIPELINE ISOLATING FITTING Figure 9.5 Resistance Test Set-Up for an Isolating Joint CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 236 Running a detailed survey or, on a pipeline, a pipe-to-soil potential profile may help in identifying the problem. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 237 Gas Venting Problems This is a common problem in deep groundbeds and in tightly packed soils. It occurs because gas (e.g., oxygen or chlorine) generated by the anodic CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 238: Routine Maintenance
• Look for significant output changes. • Smell for unusual odors (examples: rotten egg–selenium failure, ozone –insulation failure, burning–insulation failure). • Feel for unusual heat. (Turn off power before touching live components.) CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 239 The component causing the open circuit can be located by realizing that the rectifier voltage must exist across the open circuit element. If it is CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 240 Isolate shorted component by adding component by adding one component at a time one component at a time Figure 9.9 Locating a Short Circuit in a Rectifier Circuit CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 241 (”half waving”). If the rectifier stacks are found to be operating properly, the transformer should be investigated for possible winding-to-winding shorts. CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 242 RP0290 “Cathodic Protection of Reinforcing Steel in Atmospherically Exposed Structures” RP0200 “Steel Cased Pipeline Practices” TM0497 “Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems” CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 243 Appendix App:2 TM0101 “Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Storage Tanks” CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 244 Other Reference Material Primary Reference As noted in the Introduction, the primary reference for the course is Peabody’s Control of Pipeline Corrosion edited by Ronald Bianchetti (NACE International, Houston, 2001). Other Books The following books may be useful for further study and information: Parker, M.
Page 245 Repair Manual for Port and Harbor Steel Structures . Japanese Port Authority Association, “Harbor Facility Technology Criteria and Discussion, Part 1.” Japanese Water Piping Association, WSP-050, “Cathodic Protection Manual for Coated Steel Water Pipe.” CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 246 49CFR Part 192, Subpart I Natural Gas Pipelines 49CFR Part 193, Subpart G Liquefied Natural Gas 49CFR Part 195, Subpart D Hazardous Liquid Pipelines 40CFR Part 280 Underground Storage Tanks CP 1 – Cathodic Protection Tester Course Manual © NACE International, 2000 07/01/04...
Page 247 Preventing fouling. [See electrochemical cell at which reaction product. Fouling.] oxidation occurs. Electrons flow away from the anode in the © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 1 of 18...
Page 248 Whitening and loss of gloss of a by fatigue crack propagation coating, usually organic, caused [See Calcareous Coating.] © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 2 of 18...
Page 249 The development of loose, film. reaction. removable powder (pigment) at © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 3 of 18...
Page 250 (approximately 58 cm [9.0 in. of surface and may consist of light shadows, slight streaks, or © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 4 of 18...
Page 251 © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 5 of 18...
Page 252 © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 6 of 18...
Page 253 (also known © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 7 of 18...
Page 254 Corrosion that occurs under a book. FRETTING CORROSION coating in the form of randomly distributed thread-like filaments. Deterioration at the interface of © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 8 of 18...
Page 255 GALVANOSTATIC of its own ion, at a specific Refers to an experimental temperature, develops a potential © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 9 of 18...
Page 256 A nonmetallic phase such as an (also known as intercrystalline © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 10 of 18...
Page 257 A potential resulting from two or more electrochemical reactions occurring simultaneously on one metal surface. © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 11 of 18...
Page 258 NERNST EQUATION POTENTIAL application. It is commonly used An equation that expresses the The potential of an electrode © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 12 of 18...
Page 259 = -log agreement with the true value of © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 13 of 18...
Page 260 © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 14 of 18...
Page 261 Scrubbing a mixture of a cement supplying cathodic protection. Oil or grease coatings used to mortar over the concrete surface © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 15 of 18...
Page 262 STEEL SHOT respect to distance. Small particles of steel with spherical shape that are commonly used as an abrasive in © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 16 of 18...
Page 263 WATER JETTING thermal gradient. WELD DECAY Water jetting performed at pressures above 170 MPa Intergranular corrosion, usually of (25,000 psig.) © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 17 of 18...
Page 264 (usually at a strain of 0.2%) or the total- extension-under-load method (usually at a strain of 0.5%.) © 2002, NACE International. This publication may not be reprinted without the written consent of NACE International. Page 18 of 18...
Page 269 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 270 In NACE standards, the terms shall , must , should , and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual , 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements.
Page 271 RP0169-2002 ________________________________________________________________________ NACE International Standard Recommended Practice Control of External Corrosion on Underground or Submerged Metallic Piping Systems Contents 1.General ..........................1 2.Definitions ........................1 3.Determination of Need for External Corrosion Control ............ 3 4.Piping System Design ...................... 4 5.External Coatings......................6 6.Criteria and Other Considerations for Cathodic Protection..........
Page 272 Such persons may be registered corrosion on the following systems: professional engineers or persons recognized as corrosion specialists or cathodic protection specialists by NACE if their professional activities include suitable experience in 1.2.1 New piping systems: Corrosion control by a...
Page 273 Electroosmotic Effect: Passage of a charged particle measured with reference to an electrode in contact with the through a membrane under the influence of a voltage. Soil electrolyte. or coatings may act as the membrane. NACE International...
Page 274 3.2.1 Environmental and physical factors include the 3.2.2.2 Contingent costs corrosion (see following: Appendix C); and 3.2.1.1 Corrosion rate of the particular metallic 3.2.2.3 Costs of corrosion control (see Appendix piping system in a specific environment (see Appendix B); ___________________________ American Wire Gauge. NACE International...
Page 275 4.3.1.3 Inlet and outlet piping of in-line measuring manufactured to perform this function should be used, and/or pressure-regulating stations; or, if permissible, a section of nonconductive pipe, such as plastic pipe, may be installed. In either case, these NACE International...
Page 276 4.5.3.2 Methods of attaching wires to the pipe protection of pipeline(s) and personnel safety (see include (a) thermit welding process, (b) soldering, NACE Standard RP0177 and (c) mechanical means. 4.4 Electrical Continuity 4.5.3.3 Particular attention must be given to the attachment method to avoid (a) damaging or 4.4.1 Nonwelded pipe joints may not be electrically...
Page 277 5.1.2.1.11 Ease of repair; 5.1.2.1.1 Effective electrical insulator; 5.1.2.1.12 Retention of physical character- istics; 5.1.2.1.2 Effective moisture barrier; 5.1.2.1.13 Nontoxic to the environment; and 5.1.2.1.3 Application to pipe by a method that does not adversely affect the properties of the pipe; NACE International...
Page 278 Unbonded coatings can create electrical shielding of the 5.2.1.2 Damage to coating can be minimized by pipeline that could jeopardize the effectiveness of careful handling and by using proper pads and the cathodic protection system. slings. NACE International...
Page 279 Recommended Practices for Application Generic External Coating System Reference Coal Tar ANSI /AWWA C 203 NACE Standard RP0375 Prefabricated Films NACE Standard MR0274 ANSI/AWWA C 214 ANSI/AWWA C 209 Peabody’s Control of Pipeline Corrosion Fusion-Bonded Epoxy Coatings ANSI/AWWA C 213 RP 5L7 Z245.20M...
Page 280 General underground exposure with or without Peabody’s Control of Pipeline Corrosion cathodic protection ANSI/AWWA C 213 API RP 5L7 CSA Z245.20M NACE Standard RP0190 ASTM G 8 ASTM G 19 ASTM G 42 ASTM G 95 Resistance to water penetration and its effect on...
Page 281 Driving Ability (Resistance to Sliding Abrasion) ASTM G 6 ASTM D 2197 Special Requirements for Mill-Applied Coating ANSI/AWWA C 20 NACE Standard RP0375 NACE Standard MR0274 ANSI/AWWA C 214 ANSI/AWWA C 209 Peabody’s Control of Pipeline Corrosion ANSI/AWWA C 213 API RP 5L7 CSA Z245.20M...
Page 282 Recommended Test Methods Suitability of Joint Coatings and Field Repairs Peabody’s Control of Pipeline Corrosion ANSI/AWWA C 213 API RP 5L7 CSA Z245.20M NACE Standard RP0190 ASTM G 8 ASTM G 19 ASTM G 42 ASTM G 95 ASTM G 9...
Page 283 (see also Section 1, section is evidence that adequate cathodic protection Paragraphs 1.2 and 1.4). has been achieved. When excavations are made for NACE International...
Page 284 (see 6.2.2.1.1.1 Measuring or calculating references on stress corrosion cracking at the the voltage drop(s); end of this section). NACE International...
Page 285 For additional information, see Section 9, formation or decay of this polarization can be used “Control of Interference Currents.” in this criterion. 6.4 Alternative Reference Electrodes 6.2.5 Dissimilar Metal Piping 6.4.1 Other standard reference electrodes may be substituted for the saturated copper/copper sulfate NACE International...
Page 286 Barlo, T.J., and R.R. Fessler. “Interpretation of True Pipe-to- ORROSION (1957): p. 767. Soil Potentials on Coated Pipelines with Holidays.” CORROSION/83, paper no. 292. Houston, TX: NACE, 1983. ___________________________ British Standards Institution (BSI), British Standards House, 389 Chiswick High Road, London W4 4AL, United Kingdom.
Page 287 Kasahara, K., T. Sato, and H. Adachi. “Results of Pourbaix, M. Atlas of Electrochemical Equilibria in Aqueous Polarization Potential and Current Density Surveys on Solutions. Houston, TX: NACE, 1974, p. 319. Existing Buried Pipelines.” Materials Performance 19, 9 (1980): pp. 45-51. Prinz, W.
Page 288 ORROSION Barlo, T.J., et al. “Controlling Stress-Corrosion Cracking by CEA 54277. “State-of-the-Art Report, Specialized Surveys Cathodic Protection.” AGA Annual Report, Project-3- for Buried Pipelines.” Houston, TX: NACE, 1987 164, 1984. Parkins, R.N., et al. “Hydrogen Gas Evolution From Thompson, N.G., and T.J. Barlo. “Fundamental Process of Cathodically Protected Surfaces.”...
Page 289 7.3.1 Useful piping system specifications standards, and NACE standards. information include the following: 7.1.2.3 Selection and specification of materials 7.3.1.1 Route maps and atlas sheets; and installation practices that ensure dependable and economical operation throughout the intended 7.3.1.2 Construction dates;...
Page 290 Increasing the 7.5.8 Electrical resistivity of the environment. number of impressed current anodes or increasing the NACE International...
Page 291 1986. 4 (1979): pp. 34-41. Baboian, R., P.F. Drew, and K. Kawate. “Design of NACE Publication 2B160 (withdrawn). “Use of High Silicon Platinum Clad Wire Anodes for Impressed Current Cast Iron for Anodes.” C 16, 2 (1960): p. 109. ORROSION Protection.”...
Page 292 Defects in anode segments, it should be inspected and, if the cable insulation must be repaired. damaged, repaired before the anodes are installed. NACE International...
Page 293 8.5.2.4 Impressed current anodes can be buried when the connections are made. Connections of test vertically, horizontally, or in deep holes (see NACE lead wires to the pipe must be installed so they will Standard RP0572...
Page 294 However, as exist (see NACE Publication TPC 11 ). Any one or a the external coating becomes disbonded, a larger combination of the following test methods can be used.
Page 295 10.4.1 All sources of impressed current should be detailed (close-interval) potential survey should be checked at intervals of two months. Longer or shorter conducted to (a) assess the effectiveness of the intervals for monitoring may be appropriate. Evidence NACE International...
Page 296 11.2.1 Corrosion leaks, breaks, pipe replacements; and 11.4.1 Results of current requirement tests; 11.2.2 Pipe and external coating condition observed 11.4.2 Results of soil resistivity surveys; when a buried structure is exposed. 11.4.3 Location of foreign structures; and NACE International...
Page 297 Other related external 11.5.2.1.1 Location and name of company corrosion control records should be retained for such a involved; period that satisfies individual company needs. 11.5.2.1.2 Resistance value other pertinent information; and 11.5.2.1.3 Magnitude polarity drainage current. NACE International...
Page 298 Underground or Submerged Pipe” (Houston, TX: NACE). (Houston, TX: NACE). 21. DIN 30 670 (latest revision), “Polyethylene-Coatings for NACE Publication TPC 11 (latest revision), “A Guide to Steel Pipes and Fittings Requirements and Testing” (Berlin, the Organization of Underground Corrosion Control Germany: DIN).
Page 299 45. Federal Test Standard No. 406A, Method 6091 (latest 34. M. Romanoff, Underground Corrosion (Houston, TX: revision), “Test Method for Mildew Resistance of Plastics by NACE, 1989). Mixed Culture Method (Agar Medium)” (Washington, DC: General Services Administration). 35. ASTM D 427 (latest revision), “Test Method for Shrinkage Factors of Soils by the Mercury Method”...
Page 300 (e) Electrical isolation to limit possible galvanic action; and (a) Relocation of piping to avoid known corrosive conditions (this may include installing lines above ground); Correction of conditions in or on the pipe that might accelerate corrosion. (b) Reconditioning and externally coating the piping system; NACE International...
Page 301 RP0169-2002 ISBN 1-57590-035-1 NACE International...
Page 302 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 303 NACE International under the auspices of STG 35 on Pipelines, Tanks, and Well Casings. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements.
Page 304 RP0285-2002 ______________________________________________________________________________ NACE International Standard Recommended Practice Corrosion Control of Underground Storage Tanks Systems by Cathodic Protection Contents 1. General .......................... 1 2. Definitions ........................1 3. Cathodic Protection of New UST Systems ..............2 4. Cathodic Protection of Existing UST Systems ............... 5 5.
Page 305 Such individuals must either be registered buried precludes standardization of corrosion control professional engineers, NACE International Certified practices. Corrosion Specialists or CP Specialists, or individuals qualified by professional education and related 1.1.3 This standard does not include corrosion control...
Page 306 3.1.1 There are three basic types of CP available for 3.1.2 The recommended practices with respect to new UST systems: field-installed systems are similar to those for existing UST systems described in Section 4. (a) Factory-fabricated galvanic anode systems. (b) Field-installed galvanic anode systems. NACE International...
Page 307 USTs. The design specifications factory-fabricated galvanic anode CP systems consider three 3.3.4.2 When available, factory-applied coatings important factors: are preferred. The following NACE International standards may be helpful: the galvanic anodes; a dielectric coating; and RP0190; electrical isolation.
Page 308 ___________________________ Steel Tank Institute (STI), 570 Oakwood Rd., Lake Zurich, IL 60047. Underwriters Laboratories Inc. (UL), 333 Pfingsten Rd., Northbrook, IL 60062. NACE International...
Page 309 4.2.4 Other Underground Structures: The presence of additional underground structures unrelated to the tank system can affect the feasibility, type, and capacity of the proposed CP system. ___________________________ American Petroleum Institute (API), 1220 L Street NW, Washington, DC 20005. NACE International...
Page 310 DC transit systems, CP to passivate the steel. All pH testing should be done in rectifiers, DC welding equipment, and DC motors. accordance with ASTM G 51. ___________________________ ASTM International (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959. NACE International...
Page 311 5.1.5 Voltage measurements on UST systems are to (d) Determining whether or not there is physical be made with the reference electrode located on the evidence of corrosion. electrolyte surface as close as possible to the UST NACE International...
Page 312 6.2.1 This subsection describes the factors that should current and galvanic anode systems can be found in be considered in the design of external corrosion NACE Standard RP0169 and in this standard. protection for existing UST systems using galvanic Information useful in the design includes: anode CP.
Page 313 (ASTM) and the American Society of Automotive Engineers Inc. (SAE), Warrendale, PA. American Wire Gauge (AWG): A particular series of specified diameters and thicknesses established as a standard in the United States and used for nonferrous sheets, rods, and wires. Also known as the Brown and Sharpe Gauge. NACE International...
Page 314 6.3.3.6 The current requirement for achieving a (a) permanent reference electrodes, and given protection criterion can be determined by (b) portable reference electrodes inserted in access preliminary testing on existing structures through tubes. the use of temporary or simulated CP systems. NACE International...
Page 315 This work should also be coordinated with any other construction at the facility. ___________________________ The NACE International Technical Activities Division may be contacted to determine whether a UCCC is registered in the area; Call +1 281/228-6200, or e-mail tcc@mail.nace.org. NACE International...
Page 316 7.4.1 The energizing of CP systems for storage tanks free of rocks and foreign matter that might damage shall be based on the initial design parameters. Major the wire insulation when the wire is installed in a items that should be known are: trench. NACE International...
Page 317 8.1.1 Electrical measurements and inspection are practices for maintaining continuous, effective, and efficient necessary to determine that protection has been operation of CP systems on USTs. established according to applicable criteria and that each part of the CP system is operating properly. NACE International...
Page 318 8.2.2 Monitoring 8.4.3 Repair, replacement, or adjustment of continuity 8.2.2.1 All corrosion control systems shall be and interference bonds. monitored in accordance with NACE Standard TM0101 to assure effective operation as 8.4.4 Elimination of accidental metallic contact. designed. The system shall be tested to verify its effectiveness after installation and whenever 8.4.5 Repair of defective isolating devices.
Page 319 Content of Soil, Rock, and Soil-Aggregate Mixtures” (West Qualify Coating Acceptance STI-P3 Conshohocken, PA: ASTM). Specifications” (Lake Zurich, IL: STI). 15. NACE Standard RP0169 (latest revision), “Control of 6. UL 1746 (latest revision), “UL Standard for Safety, External Corrosion on Underground or Submerged External Corrosion Protection Systems Steel Metallic Piping Systems”...
Page 320 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 321 It is issued by NACE International under the auspices of STG 30. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9.
Page 322 RP0176-2003 ________________________________________________________________________ NACE International Standard Recommended Practice Corrosion Control of Steel Fixed Offshore Structures Associated with Petroleum Production Contents 1.General ..........................1 2.Definitions ........................1 3.Structural Design for Corrosion Control ................3 4.Criteria for Cathodic Protection..................6 5.Design of Cathodic Protection Systems................9 6.Installation of Cathodic Protection Systems..............
Page 323 Section 2: Definitions NOTE: Additional definitions for cathodic protection and Cathodic Protection: A technique to reduce the corrosion coatings technology may be found in NACE Standard of a metal surface by making that surface the cathode of an RP0169, the NACE Corrosion Engineer’s Handbook, electrochemical cell.
Page 324 Structure: Stationary structure (platform or subsea facility) “J” Tube: A curved tubular conduit designed and installed that is fixed to the sea floor by gravity, piling, and/or mooring cables. on a structure to support and guide one or more pipeline risers or cables. NACE International...
Page 325 3.2.2 A structure should be designed to minimize the ably be clamped to the structural member, not welded surface area of steel in the splash zone. Intersecting to it. “T,” “K,” and “Y” joints should be avoided in the splash zone. NACE International...
Page 326 “I” beams are difficult to protect. The crevice connected to the CP system. formed by placing angles or channels back-to- ___________________________ American Petroleum Institute (API), 1220 L St. NW, Washington, DC 20005. NACE International...
Page 327 “J” tubes. To restrict contact with seawater and at- tection measures taken in the form of CP, coating, mospheric oxygen, the pull-tube annulus should be or corrosion allowance. sealed at the above-water end with a suitable nonwick- NACE International...
Page 328 0.125% maximum. (see Paragraphs 4.5.1.1 and 4.6.1). __________________________________________ ASTM International, 100 Barr Harbor Drive, West Conshochocken, PA 19428. Military Specification, available from Government Printing Office, Washington, DC 20402. NACE International...
Page 329 4.5.1.5 A number of permanent reference elec- CP current. trodes may be mounted on a structure. While the exact electrode locations are known, the informa- tion obtained from these electrodes is limited to the adjacent structure surfaces. NACE International...
Page 330 Nomogram for the correction of potential readings made with the Ag/AgCl electrode in waters of varying (4),9 resistivity to the saturated calomel or Cu/CuSO scale. ___________________________ Nomogram courtesy of M.H. Peterson, Naval Research Laboratory (NRL), Washington, DC and R.E. Groover, NRL Marine Corrosion Laboratory, Key West, FL. NACE International...
Page 331 CP can be effi- (a) Structure operator, ciently satisfied. (b) NACE International, 5.2.2 To minimize the effect on associated pipelines or other neighboring metallic structures that may be (c) API, caused by the operation of the proposed system.
Page 332 (c) Adjacent facilities, including pipelines, material should be capable of supplying current even after many years of very low anodic current (d) Existing and proposed CP systems, and density. (e) Electrical isolation from foreign pipelines or 5.4.2 Impressed current anode systems structures. NACE International...
Page 333 (see Appendixes): mens, Hartt and Lemieux proposed that design mean current density, i , conform to the expres- (a) Resistivity of the electrolyte, sion used in Equation (1): σ (b) Anode-to-structure potential (when structure is at × protected level), NACE International...
Page 334 (usually in the visual inspection of the coating deterioration indi- range of 67 to 80%) should be used. The CP sys- cates. tem should be sized to provide 1.25 to 1.50 times NACE International...
Page 335 The shape of the anode affects the utilization factor. experience shows that the intended anode mater- Proper selection of length, diameter, and core diameter NACE International...
Page 336 Warpage is acceptable if it does not ad- assistance. versely affect the anode installation. More specific guidelines can be found in NACE Standard (c) Anodes can be installed on submerged RP0387. structure members using offset steel structural supports attached to the structure members.
Page 337 ________________________________________________________________________ Section 6: Installation of Cathodic Protection Systems 6.1 Introduction 6.4.1.1 Specific guidelines can be found in NACE Standard RP0387. 6.1.1 This section recommends procedures for instal- ling CP systems in accordance with design consider- 6.4.1.2 Anodes should be inspected to ensure...
Page 338 6.6.1.2 Both the pipe and the test lead wires should be clean, dry, and free of foreign material 6.5.2.2 Wiring to rectifiers shall comply with any at points of connection when the connections are applicable regulatory codes and with the oper- NACE International...
Page 339 These mitigation procedures should be performed in barge, and (b) the grounding cable from each machine cooperation with other companies or operators, when should be connected to the structure. Alternatively and applicable. preferably from a corrosion standpoint, the barge oper- NACE International...
Page 340 9.2.1 Electrical measurements and inspections are tion, number, and type of electrical measurements necessary to determine that protection has been est- used to determine the adequacy of CP (see Section 4). ablished according to applicable criteria and that each NACE International...
Page 341 If the original CP design was and overall circuit resistance. conservative, the actual remaining anode life may be well in excess of two years. This actual __________________________________________ Bureau of Mines, 2402 E Street NW, Washington, DC 20241. NACE International...
Page 342 Automotive Engineers (SAE), 400 Commonwealth Drive, Warrendale, PA 15096. American Wire Gauge (AWG): A particular series of diameters and thicknesses established as a standard in the United States and used for nonferrous sheets, rods, and wires. Also known as the Brown and Sharpe Gauge. NACE International...
Page 343 11.2.1 The splash zone interval should be visually in- ments should be made to determine that the loss does spected annually to determine whether corrosion con- not exceed the corrosion allowance. trol is still effective. If failure has occurred, the extent of NACE International...
Page 344 SSPC SP 1. scale exposed before or during operations shall be re- moved prior to surface preparation. ___________________________ ( 9) SSPC: The Society for Protective Coatings, 40 24 St., 6 Floor, Pittsburgh, PA 15222-4656. NACE International...
Page 345 Methods resulting in polishing of the steel surface, e.g., wire 12.3.1.3 NACE No. 3/SSPC SP 6 states that a brushing, shall not be used. commercial blast-cleaned surface, when viewed without magnification, shall be free of all visible oil, 12.3 NACE Surface Preparation Standards...
Page 346 Zinc-rich primers are ___________________________ (10) Bureau of Mines, 2402 E. Street NW, Washington, DC 20241. NACE International...
Page 347 The change from ating materials are: a liquid to a solid state is not accompanied by any chemical change. This mode of drying permits NACE International...
Page 348 The materials 13.6.2 Clean cans and strainers should be provided should be stored in a manner that prevents exposure to for mixing the coating materials. NACE International...
Page 349 13.8 Coatings for Production Equipment and Piping located on Structures (b) Condition of steel, 13.8.1 For most equipment operating at ambient tem- (c) Protection of production equipment required, peratures, many of the systems listed in Table 3 are in widespread use. NACE International...
Page 350 14.2.2 Inspectors should acquaint themselves with the hoses, and that gaskets and nozzles are properly materials to be used on the job. sized and in good condition. Air quality should be checked for cleanliness and dryness (see Para- NACE International...
Page 351 14.4.4 A set of NACE surface preparation standards the materials to be applied. Documentation of ver- for comparing surface preparation is recommended ifications should be made.
Page 352 15.2.1.4 Number and location of anodes if checked either during construction or after setting 15.2.5.1 Results of underwater inspection of the on location, with all discrepancies noted. anode system, noting all discrepancies such as missing anodes. NACE International...
Page 353 PA: ASTM). R. Baboian, ed., NACE Corrosion Engineer’s Refer- MIL-A-18001 (latest revision), “Anodes, Sacrificial Zinc ence Book, 3rd ed. (Houston, TX: NACE, 2002). Alloy” (Washington, DC: Government Printing Office). NACE International 2002 Glossary of Corrosion-Rel- “Tests Indicate the Ag/AgCl Elec Is Ideal Reference ated Terms (Houston, TX: NACE, 2002).
Page 354 PA: SSPC). Testing Water Resistance of Coatings in 100% Relative Humidity” (West Conshohocken, PA: ASTM). 15. NACE No. 1/SSPC-SP 5, “White Metal Blast Cleaning” (Houston, TX: NACE, and Pittsburgh, PA: SSPC). 28. ASTM D 522 (latest revision), “Standard Test Methods for Mandrel Bend Test of Attached Organic Coatings”...
Page 355 82-86. 40. J.E. McCoy, “Corrosion Control Cathodic 41. NACE Publication 7L198 (latest revision), “Design of Protection,” in Transactions of the Institute of Marine Galvanic Anode Cathodic Protection Systems for Offshore Structures” (Houston, TX: NACE). _________________________________________________________________________________________________________________ Bibliography Anthony D.R. “Unique Methods for Applying and Monitor- Designing Impressed Current Cathodic Protection Systems ing Platform Cathodic Protection in Cook Inlet, Alaska.”...
Page 356 Offshore Technology Conference, paper no. 4971 tion of Guyed Tower in 1,000 ft of Water.” CORRO- (1985). SION/87, paper no. 76. Houston, TX: NACE, 1987. Thomason, W.H., S.E. Pape, and S. Evans. “The Use of Reding, J.T., and T.D. Boyce. “Cathodic Protection Perfor-...
Page 357 Current density is strongly dependent on water temperature. For deep-water structures different design values should be used for different temperature zones. To optimize the de- sign the structure should be spilt up into separate zones NACE International...
Page 358 Examples of these calculations are given in Appendixes D and E. Final current densities are calculated in a manner similar to the initial current density, except that the depleted anode dimensions are used. An example of this calculation is given in Appendix D. NACE International...
Page 359 The above data show ranges that are taken from field tests at Key West, Florida, by Naval Research Laboratory, Washington, DC, from manufacturers’ long-term field tests. Modification to these numbers will be made only by recommendation from NACE International STG 30 on Oil and Gas Production—Cathodic Protection.
Page 360 (mean current R = anode-to-electrolyte resistance in ohms requirement), and to produce enough current to maintain ρ = resistivity of the electrolyte in ohm-cm. (See Table protection at the end of the design life (final current require- NACE International...
Page 361 The number of anodes required to protect a structure with 9,300 m (100,000 ft ) of exposed surface area is as shown in Equation (D7): Final Current Density mA/m × Surface Area 9,300 anodes (D7) Amps output anode 4.78 × 1,000 mA/A NACE International...
Page 362 , which results (a) Select a candidate anode, and from its dimensions from that design slope. Again, separate designs may be calculate its resistance, R , and its mass, w. executed for different regions of the structure. NACE International...
Page 363 6 above. The area protected by each anode type is different. = area protected per anode in m NACE International...
Page 364 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 365 STG 05. In NACE standards, the terms shall , must , should , and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual , 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements.
Page 366 RP0388-2001 ________________________________________________________________________ NACE International Standard Recommended Practice Impressed Current Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks Contents 1. General.......................... 1 2. Definitions........................1 3. Determination of the Need for Cathodic Protection............2 4. Design of Impressed Current Cathodic Protection Systems......... 3 5.
Page 367 Such persons may be registered professional 1.5 Cathodic protection, as described in this standard, may engineers or persons certified by NACE International as be used alone to control corrosion of submerged steel Cathodic Protection or Corrosion Specialists, if their...
Page 368 3.1.3 Cathodic protection is effective in controlling 3.2.3 The current required for cathodic protection is corrosion only on the submerged metal surfaces. lowered significantly when coatings are also used. 3.2.4 The coating system should be compatible with cathodic protection. NACE International...
Page 369 (m) Other pertinent information, including age and storage tanks. history of tank; and whether the tank is of welded, bolted, or riveted construction; and area classification. NACE International...
Page 370 10 to 20% for a 20-year accumulation on the anodes or in a solid mass system design life. across the tank, which could damage the anodes when collapsing. NACE International...
Page 371 Metals and Alloys in the Unified Numbering System (latest revision), a joint publication of the American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA 19428, and the American Society of Automotive Engineers Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096. NACE International...
Page 372 6.2.1 A negative, polarized tank-to-water potential of at least -850 mV relative to a saturated copper/copper 6.3.2 A sufficient number of potential measurements sulfate reference electrode (CSE); or should be taken to determine that adequate protection NACE International...
Page 373 ±10 mV when compared with a new electrode. Consideration should be given to providing current- When the potential difference exceeds ±20 mV, the limiting devices to prevent excessive current outputs electrode shall be replaced. that may be harmful to the coating (see Paragraph 6.4). NACE International...
Page 374 Any breaks in the wiring insulation must repaired. insulation NACE International...
Page 375 ________________________________________________________________________ References 1. NACE Standard RP0196 (latest revision), “Galvanic 2. NSF-61 (latest revision), “Drinking Water System Anode Cathodic Protection of Internal Submerged Surfaces Components” (Ann Arbor, MI: NSF International). of Steel Water Storage Tanks” (Houston, TX: NACE). NACE International...
Page 376 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 377 Unit Committee T-10B on Interference Problems. The NACE technical committee structure changed in 2000, following the reaffirmation of this standard. This standard is issued in 2000 by NACE International under the auspices of STG 05 on Cathodic/Anodic Protection.
Page 378 RP0177-2000 _______________________________________________________________________ NACE International Standard Recommended Practice Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems Contents 1. General ........................1 2. Definitions ......................... 1 3. Exposures and Effects of Alternating Current and Lightning ........3 4.
Page 379 NACE International if their professional for cathodic protection systems on structures subject to activities include suitable experience in corrosion control AC influence.
Page 380 AC. separated by a distance equal to the normal maximum horizontal reach of a human (approximately 1.0 m [3.3 Potential: See Electric Potential. ft]). Potential Gradient: Change in the potential with respect to distance. NACE International...
Page 381 If the structures. NACE International...
Page 382 4.4.2 When an independent metallic structure or its Permanent grounding mats bonded to the structure grounding system is in close proximity to an existing may be used at valves, metallic vents, cathodic grounded structure, an electrical hazard may develop NACE International...
Page 383 Dissipation of the anode material increases the grounding system resistance. ____________________________ Institute of Electrical and Electronics Engineers (IEEE), 3 Park Avenue, 17 Floor., New York, NY 10016-5997. NACE International...
Page 384 1. Find C (average specific heat) in “(cal/g)(ºC)” or “BTU/([lb][ F])” from handbook tables. 2. Substitute M (mass) with “0.002205 x M ” where M = mass of copper in grams. 3. Substitute T + 17.78)(1.8) and T + 17.78)(1.8). NACE International...
Page 385 RP0177-2000 Figure 1—Approximate current required to raise the temperature of stranded annealed soft-drawn copper cable 684ºC (1,232ºF) above an ambient temperature of 20ºC (68ºF) NACE International...
Page 386 Figure 2 — Allowable short circuit currents for insulated copper conductors. Reprinted with permission from Insulated Cable Engineers Association (ICEA). Publication P-32-382, copyright 1994. ____________________________ To calculate this formula using metric units, change A to metric values as indicated in Table A1, Appendix A. NACE International...
Page 387 Figure 3 — Allowable short circuit currents for insulated copper conductors. Reprinted with permission from Insulated Cable Engineers Association (ICEA). Publication P-32-382, copyright 1994. ____________________________ To calculate this formula using metric units, change A to metric values as indicated in Table A1, Appendix A. NACE International...
Page 388 In some cases, the electric utility can shut down the electrical transmission facility or block the reclosing features. The utility may designate a coordinator while the project is in progress. These possibilities should be explored with the electric utility. NACE International...
Page 389 (or some grounding procedures and of the dangers associated other adjacent structure) shall be considered an with inductive and capacitive couplings, fault current, indication that further study is required. lightning, etc., on aboveground and underground NACE International...
Page 390 35-mm (0.054-in. ) (No. 2 AWG) are subject to existing electrical safety regulations stranded welding cable equivalent when operated in the vicinity of high-voltage AC recommended. See Table 1 and Figures 1, 2, and 3 lines. NACE International...
Page 391 6.2 Determination of AC Influence and Lightning Effects effects to which an existing metallic structure may be subjected. This section also outlines several points 6.2.1 A cathodic protection system design should consideration regarding effects these include an evaluation to estimate the level of AC NACE International...
Page 392 Survey data gathered in accordance with Paragraphs 6.2.3 through 6.2.3.4 should be reviewed with electric utility personnel for the purpose of correlating with the power-line operating conditions at the time of the survey. NACE International...
Page 393 (b) Heavy-duty choke coils installed in the AC 7.2.7 When long test leads are laid out near a power and/or DC leads. line, significant potentials may be induced in these leads. The hazards associated with this situation may be reduced by using the following procedures: NACE International...
Page 394 (10) Occupational Safety and Health Administration (OSHA), 200 Constitution Ave. NW, Washington, DC 20210. (11) American Gas Association (AGA), 1515 Wilson Blvd., Arlington, VA 22209. (12) Electric Power Research Institute (EPRI), 3412 Hillview Ave., Palo Alto, CA 94304-1395. NACE International...
Page 395 Toronto, Ontario, Canada: Canadian Gas Association. Some Considerations During Construction Near Powerlines (latest revision), NACE Audio/Visual Gummow, R.A., R.G. Wakelin, and S.M. Segall. “AC Presentation Prepared by Work Group T-10B-5a. Houston, TX: NACE, 1983. Corrosion A New Challenge to Pipeline Integrity.”...
Page 396 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 397 In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements.
Page 398 RP0575-2001 ________________________________________________________________________ NACE International Standard Recommended Practice Internal Cathodic Protection Systems in Oil-Treating Vessels Contents 1. General.......................... 1 2. Definitions........................1 3. Determination of Need for Cathodic Protection............. 2 4. Design and Selection of Cathodic Protection System ........... 2 5. Anode Installation......................4 6.
Page 399 (sometimes referred to as cathodic solution potential). Electrolyte: A chemical substance containing ions that migrate in an electric field. For the purpose of this standard, NACE International...
Page 400 (d) vessel configuration; and necessary to make modifications or redesign the vessel interior to provide access to areas needing (e) desired life of the cathodic protection system. cathodic protection by installing fittings in the vessel for NACE International...
Page 401 4.2.4 Galvanic anode materials most commonly used are aluminum, magnesium, and zinc alloys. NACE International...
Page 402 5.2.2 Alternatively, galvanic anodes may be bolted or considered, they must be properly designed to provide welded to brackets permanently affixed to the vessel isolation between the anode mounting head and the surface. However, this type of installation does not vessel. NACE International...
Page 403 Current measurements can be obtained through a full-opening valve installed in the vessel by measurement of the potential across the shunt of for that purpose (see Paragraph 6.1.2). Reference known resistance. electrodes manufactured to withstand pressure NACE International...
Page 404 Additional information on the toxicity of H codes, including OSHA regulations. ________________________________________________________________________ References 1. NACE Publication 35201 (latest revision), “Report on the N. Irving Sax, Dangerous Properties of Industrial Application and Interpretation of Data from External Materials (New York, NY: Reinhold Book Corp., 1984).
Page 405 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 406 International under the auspices of STG 35 on Pipelines, Tanks, and Well Casings. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements.
Page 407 RP0193-2001 ________________________________________________________________________ NACE International Standard Recommended Practice External Cathodic Protection of On-Grade Carbon Steel Storage Tank Bottoms Contents 1. General ........................... 1 2. Definitions ........................1 3. Preliminary Evaluation and Determination of the Need for Cathodic Protection..... 2 4. Criteria for Cathodic Protection..................5 5.
Page 408 On-Grade Storage Tank: A tank constructed on sand or Electrical Isolation: The condition of being electrically earthen pads, concrete ringwalls, or concrete pads. separated from other metallic structures or the environment. NACE International...
Page 409 3.3.1.4 Data pertaining to existing corrosion conditions should be obtained in sufficient quantity permit reasonable engineering judgments. Statistical procedures should be used in the analysis, if appropriate. NACE International...
Page 410 Figure 1: Soil Resistivity Testing (Four-Pin Method) Note: a = Depth of interest for the soil resistivity measurement. ___________________________ American Society for Testing and Materials (ASTM), 100 Barr Harbor Dr., West Conshohocken, P.A. 19428. NACE International...
Page 411 Possible sources of stray current include DC-operated rail systems and mining operations, other cathodic protection systems, welding equipment, and high-voltage direct current (HVDC) transmission systems. ___________________________ U.S. Geological Survey Office, P.O. Box 25046. Federal Center, Denver, CO 80225. NACE International...
Page 412 The can be demonstrated by other means that the control selection of a particular criterion for achieving this of corrosion has been achieved. objective depends, in part, on prior experience with NACE International...
Page 413 4.3.1.3 A minimum of 100 mV of cathodic least 850 mV with the cathodic protection current polarization between the carbon steel surface of applied. This potential shall be measured with the tank bottom and a stable reference electrode NACE International...
Page 414 Anode selection should be based (see Paragraph 11.2) soil chemistry, contaminants, compatibility of the anode with the environment. 5.2.2 General characteristics of impressed current and galvanic current cathodic protection systems are listed NACE International...
Page 415 (1 to 2 mA/ft ) of bare tank bottom surface are bottoms. Clean, fine sand is the preferred tank pad material. generally sufficient. Systems exposed to chemistry involving chlorides, sulfides, or bacteria or to elevated NACE International...
Page 416 DC generator. The tank bottom shall be electrically connected to the negative terminal. Cable insulation should be selected based on the anticipated environmental conditions and should be resistant to oil and water. Sand Figure 4: Vertically Drilled Anode CP System NACE International...
Page 417 Figure 7: Horizontally Installed Anode Groundbed 6.2.3 Deep anode systems should be designed and a given output, the anode life depends on the installed in accordance with NACE Standard RP0572. environment, anode material, anode weight, and the number of anodes in the cathodic protection system.
Page 418 7.3.5 Zinc anodes should not be used if the temperature of the anode environment is above 49°C (120°F). Higher temperatures can cause passivation of the anode. The presence of salts such as carbonates, NACE International...
Page 419 NACE International...
Page 420 8.4.4 Anodes must be installed in a conductive current anode design. electrolyte. The electrolyte must be sufficiently compacted as to prevent settlement of the replacement 8.4.1.3 Due to the depolarizing effect of tank bottom. oxidation by-products (typically chlorine, oxygen, NACE International...
Page 421 RP0193-2001 Tank Shell Figure 9: Typical Double-Bottom Galvanic Anode Design Tank Shell Wire Anode Figure 10: Typical New Tank or Double-Bottom Impressed Current Anode Design NACE International...
Page 422 Figure all tanks regardless of the groundbed type and 11 illustrates the placement of perforated pipe installed location. for a reference electrode. 9.4.1.1 Stationary reference electrodes may be prepackaged in a backfill and placed in the soil NACE International...
Page 423 9.5.5 The test station or junction box in a galvanic system may be equipped with calibrated resistors (shunts) in connections between the anodes and the tank to measure the anode current output and thus the estimated anode life. Shunts are typically rated between 0.001 and 0.1 ohm. NACE International...
Page 424 Those parameters should include: diameter tank does not represent the potential at the center of the tank. (a) Initial baseline data (b) As-built drawings NACE International...
Page 425 11.4 Corrective action shall be taken if surveys and the bottom on tanks of 18-m (60-ft) diameter or less. inspections indicate that the cathodic protection system is On tanks greater than 18 m (60 ft) in diameter, eight NACE International...
Page 426 Using Electromagnetic Conductivity Measurement Techniques,” ASTM Standard B 418 (latest revision), “Standard CORROSION/87, paper no. 130 (Houston, TX: NACE Specification for Cast and Wrought Galvanic Zinc International, 1987). Anodes” (West Conshohocken, PA: ASTM). ________________________________________________________________________ Bibliography Ewing, S.P. “Potential Measurements for Determination of McDorman, O.N.
Page 427 RP0193-2001 NACE Publication 56-12. “Contributions of J.M. Pearson Pearson, J.M. “Electrical Instruments and Measurements to Mitigation of Underground Corrosion.” Houston, in Cathodic Protection.” Corrosion 3, 11 (1947): p. TX: NACE, 1956. (Out of print). 549. NACE Standard RP0169 (latest revision). “Control of “Underground Corrosion.”...
Page 428 Nothing contained in this NACE standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 429 CP system described in this standard may not be practical for relatively large tanks. This standard was originally prepared in 1996 by NACE Task Group (TG) T-7L-1, a component of Unit Committee T-7L on Cathodic Protection. It was revised in 2004 by TG 284 on Cathodic Protection, Galvanic Anode for Internal Submerged Surfaces of Steel Water Storage Tanks—...
Page 430 RP0196-2004 ________________________________________________________________________ NACE International Standard Recommended Practice Galvanic Anode Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks Contents 1. General......................... 1 2. Definitions........................1 3. Determination of Need for CP ..................2 4. Design of Galvanic Anode CP System ................. 3 5.
Page 431 Corrosion 1.5 CP as described in this standard may be used alone to Specialists or CP Specialists by NACE if their professional control corrosion of submerged steel surfaces or may be activities include suitable experience in corrosion control used as a complement to the protection provided by and CP.
Page 432 3.1.3 CP is effective in controlling corrosion only on 3.2.4 The current required for CP is much lower for coated steel tanks compared with bare or poorly submerged metal surfaces during submersion. It does not reverse structural damage already caused by coated steel tanks. corrosion. NACE International...
Page 433 The cost poorly coated steel tank with an impressed current of installing CP, projected maintenance costs, and system. This method is described in NACE Standard monitoring costs should be compared with the cost of RP0388.
Page 434 Table 1. on which the anode can be supported either vertically or horizontally. NACE International...
Page 435 5.3.1 All construction work should be performed by, or 5.2 Construction Specifications under the direction of, a person who is qualified by experience in the installation of galvanic anode CP systems in water storage tanks, and who should verify NACE International...
Page 436 6.4.1 Potential measurements on water tank interiors should be made with the reference electrode located in the water (electrolyte) as close as possible to the tank steel surface. Consideration shall be given to voltage NACE International...
Page 437 Paragraph 6.3 are being achieved. The potential and current output 7.3.2.3.3 For installations which shall be monitored and the circuit resistance stationary reference electrode is not installed or is not functioning, a calibrated portable NACE International...
Page 438 (d) Wiring and anode suspension, 7.5.1.1 Complete information and the history of the tank itself should be recorded, including: (e) Electrical schematic diagrams, (a) Dimensions and capacity, Individual galvanic anode circuits and shunt resistances, (b) Tank erection and CP contractor, NACE International...
Page 439 These measurements (d) Costs of maintenance including coating, CP should be taken when the tank is relatively full. inspections, etc. ________________________________________________________________________ References NACE Standard RP0388 (latest revision), “Impressed Components—Health Effects” (Ann Arbor, MI: NSF Current Cathodic Protection Internal Submerged International).
Page 440 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 441 In NACE standards, the terms shall , must , should , and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual , 3 ed., Paragraph 8.4.1.8.
Page 442 RP0290-2000 _______________________________________________________________________ NACE International Standard Recommended Practice Impressed Current Cathodic Protection of Reinforcing Steel in Atmospherically Exposed Concrete Structures Contents 1. General ........................1 2. Criteria ........................1 3. Design of Impressed Current Cathodic Protection Systems......... 4 4. Installation Practices....................6 5.
Page 443 Professional consists of four components: an anode, where Engineer or a person certified by NACE International oxidation occurs; a cathode, where reduction occurs; a as a Corrosion Specialist or certified as a Cathodic metallic path, where the electric current is electron flow;...
Page 444 Figure 1 depicts a typical polarization decay curve. The polarization equals the instant-off potential 2.3 NACE Work Group T-11-1a developed these criteria subtracted from reinforcement’s final through empirical evaluation of data obtained from “depolarized potential.”...
Page 445 Longer periods of engineer shall monitor for the impact of these decay or polarization development are required for phenomena throughout the test period to ensure NACE International...
Page 446 108 mA/m Sustained operation at current densities above 3.3.2 Condition survey (in accordance with ACI 201 these levels may result in deterioration of the concrete at the anode-concrete interface. 3.3.3 Potential survey (in accordance with ASTM C 876) NACE International...
Page 447 Tolerances should be stated. Electrical Code issued by the NFPA, those issued by OSHA, NEMA, NACE, ACI, ASTM, and any 3.5.10 In areas where stray currents are suspected, other applicable codes or standards should be appropriate tests should be conducted. Special specified.
Page 448 National Electrical Code, those issued by OSHA, NEMA, NACE, ACI, ASTM, and any other 4.3.2 Equipment used for installation shall be in applicable codes or standards.
Page 449 The effectiveness of 6.6 An operations and maintenance manual that includes continuity bonds and isolation of cathodic protection circuits the following information should be provided. should be evaluated during the periodic surveys. These NACE International...
Page 450 The following data should be part of the records: 7.6 The operation and maintenance manual shall become a part of the permanent records for the system. 7.3.1 Electrical continuity verification. 7.3.2 Tests for electrical shorts. NACE International...
Page 451 Corrosion Testing” (West Conshohocken, PA: ASTM). Reinforced Concrete Structures” (Houston, TX: NACE). ACI 201 (latest revision), “Guide for Making a condition Work in Progress by NACE Task Group T-11-1d, Survey of concrete in Service” (Farmington Hills, MI: ACI). “Criteria for Cathodic Protection of Prestressed Concrete Structures”...
Page 452 STP-818 (latest revision), “Corrosion Metals Association with Concrete.” J. Slater, ed. West Collected NACE Papers 1976-1982 . Houston, TX: NACE. Conshohocken, PA: ASTM. _______________________________________________________________________ Appendix A— Glossary of Terms Attenuation: Electrical losses in a conductor caused by Design Specifications: A set of documents that, in current flow in the conductor.
Page 453 Current distribution Other embedments Anode current densities Overlays, sealers, membranes Instrumentation for monitoring Chloride test and chemical analysis Physical, electrical, and environmental protection Chloride source of components Potential survey Maintenance interval Delamination survey Materials m. Cover survey Equipment NACE International...
Page 454 Portable reference electrodes pH testing equipment DC source: generator/battery Resistivity meter—AC type Equipment for use during current requirement tests Sulfate and chloride test equipment Reinforcement depth-of-cover meter DC voltmeter with variable input impedance 10. Metal detector ISBN 1-57590-103-X NACE International...
Page 455 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 456 NACE International under the auspices of Group Committee T-10 on Underground Corrosion Control. In NACE standards, the terms shall , must , should , and may and are used in accordance with the definitions of these terms in the NACE Publications Style Manual , 3rd ed., Paragraph 8.4.1.8.
Page 457 RP0200-2000 _______________________________________________________________________ NACE International Standard Recommended Practice Steel-Cased Pipeline Practices Contents 1. General........................1 2. Definitions......................... 1 3. Design ........................1 4. Installation ........................ 2 5. Maintenance and Repair ................... 4 6. Monitoring......................... 5 References........................6 Bibliography ........................6 Appendix A: Typical Casing-Filling Procedures.............. 7 Appendix B: Monitoring Techniques ................
Page 458 For pipelines smaller than 20 cm (8.0 with consideration being given to the application of in.) in diameter, the diameter of the casing is supplementary coating. See NACE Standard normally a minimum of 5 cm (2 in.) larger than that RP0169 for details.
Page 459 3.2.8 Vent pipes shall be designed, using standard some situations, and applied to the casing as industry methods, to exclude intrusion of water and required by conditions and/or regulations. debris. NACE Standard RP0169 for details. 3.4.2 Consideration be given placing 3.3 Metallic Isolation inhibited dielectric filler in the annular space.
Page 460 The use of color-coded test lead wires installation. (See NACE Standard RP0286 for is desirable. additional information.) 4.6 Backfilling: The casing and carrier pipe shall be 4.4.3 The casing shall be visually inspected and, if...
Page 461 (shorted to) the carrier pipe. and vent caps. Test leads shall be checked annually to • The casing becomes filled or partially filled with determine their integrity. electrolyte and an internal “electrolytic” contact develops. NACE International...
Page 462 (two on technique uses a four-pin resistance meter or casing, two on carrier pipe) are used to conduct the megger to determine the as-found resistance test. between the carrier and casing. NACE International...
Page 463 _______________________________________________________________________ References NACE Standard RP0169 (latest revision), “Control of NACE Standard RP0490 (latest revision), “Holiday External Corrosion on Underground or Submerged Detection of Fusion-Bonded Epoxy External Pipeline Coatings of 250 to 760 µm (10 to 30 mils)” (Houston, TX: Metallic Piping Systems”...
Page 464 • percentages provides a useful measure of the overall Failure to take into account the displacement of the performance of the casing-filling procedure. An average isolators casing-fill percentage lower than 85% is considered questionable and should be investigated. NACE International...
Page 465 1.6 V CSE and a testing should be conducted if the difference in potential casing potential of 0.65 V CSE has a potential difference is 100 mV or less. of 0.95 volts and would indicate the casing is clear. NACE International...
Page 466 If a four-pin soil resistivity meter is used, the locations of the test leads are the same as those shown in Figure B2. C1 is connected to T3, P1 to T1, P2 to T2, and C2 to T4. NACE International...
Page 467 The battery current in amperes is divided by Measuring the Linear Resistance of the Casing the change in potential difference from T3 to T4 (∆V) in mV to express the calibration factor in A/mV, as shown in Equation (B3). NACE International...
Page 468 (T4) is calculated using The inside terminals T3 and T4 are the same Equation (B6). as those used for the measurement of potential ∆ (B6) (T4) Calibratio Factor Distance (in percent) from T4 = 100% Current NACE International...
Page 469 A M- METER BA TTERY PIPE V ENT PIPE V OLT LEA D METER GROUND LEVEL TEST LEA D CARRIER PIPE CASING U/S End D/S End FIGURE B4: Establishing a Circuit for a Four-Wire IR Drop Test (U/S End) NACE International...
Page 470 Length b = 15 m (49 ft) Diameter = 76.2 cm (30.0 in.) Wall Thickness = 7.92 mm (0.312 in.) Potential Difference Before Current is Applied: 0.465 mV Potential Difference After Current is Applied: -1.500 mV -1.035 mV Change in Potential (∆V): NACE International...
Page 471 A/m (A/ft) (as shown in Step 2). If the currents do not sum algebraically, the results of the testing shall be considered inconclusive. NACE International...
Page 472 Step 1 shall be repeated at the same instant rods driven into the earth or sheets of aluminum foil that the cathodic protection current is switched off. in contact with the earth (usually placed in standing water) may provide an adequate temporary structure. NACE International...
Page 473 Step 1 Volts 0.0860 Amps 1.139 0.700 0.4390 Step 2 Volts 0.258 Amps 1.104 0.140 0.9640 Step 3 Volts 0.413 Amps 1.060 +0.240 1.300 Step 4 Volts 0.566 Amps 1.022 +0.490 1.512 Conclusion: Casing is clear (not shorted). NACE International...
Page 474 The presence and location of a pipe-to-casing metallic contact may also be approximated by following a low-power audio or radio signal (pipe locator trace) set between the pipe and the casing. The signal returns at the point of contact, which shoul d be verified from the opposite end. NACE International...
Page 475 92.400 303.15 1.017 3.338 10.174 176.24 0.25 54.63 36.71 39.054 128.13 1.117 3.665 11.171 193.52 7.92 0.312 67.98 45.68 20.6 6.27 48.597 159.44 1.117 3.665 11.171 193.52 0.25 62.58 42.05 22.3 6.81 44.735 146.77 1.277 4.189 12.767 221.17 NACE International...
Page 476 20.750 359.40 8.26 0.325 132.6 89.12 10.5 3.21 94.811 311.06 2.075 6.807 20.750 359.40 9.53 0.375 152.73 102.63 9.15 2.79 109.19 358.22 2.075 6.807 20.750 359.40 12.7 0.500 202.65 136.17 6.89 2.10 144.87 475.29 2.075 6.807 20.750 359.40 NACE International...
Page 477 0.50 377.52 253.68 3.71 1.13 269.89 885.45 3.8301 12.566 38.301 663.50 48.0 15.9 0.625 470.67 316.27 2.99 0.910 336.472 1,103.91 3.8301 12.566 38.301 663.50 48.0 0.75 563.31 378.52 2.49 0.760 402.699 1,321.19 3.8301 12.566 38.301 663.50 ISBN 1-57590-094-7 NACE International...
Page 478 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 479 Because the measurements are obtained under widely varying circumstances of field conditions and pipeline design, this standard is not as prescriptive as those NACE standard test methods that use laboratory measurements. Instead, this standard gives the user latitude to make testing decisions in the field based on the technical facts available.
Page 480 TM0497-2002 ________________________________________________________________________ NACE International Standard Test Method Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems Contents 1. General......................... 1 2. Definitions........................1 3. Safety Considerations ....................3 4. Instrumentation and Measurement Guidelines............. 3 5.
Page 481 Definitions in this section reflect common usage among practicing corrosion control personnel and apply specifically to how terms are used in this standard. As much as possible, these definitions are in accord with those in the “NACE Glossary of Corrosion-Related Terms”...
Page 482 Wire: A slender rod or filament of drawn metal. In practice, the term is also used for smaller gauge conductors (size 6 Reference Electrode: An electrode whose open-circuit [No. 10 AWG ] or smaller). potential constant under similar conditions ___________________________ American Wire Gauge (AWG). NACE International...
Page 483 3.1.8 Observe appropriate electrical codes 3.1.3.1 Refer to NACE Standard RP01772 for applicable safety regulations. additional information about electrical safety. ________________________________________________________________________ Section 4: Instrumentation and Measurement Guidelines 4.1 Cathodic protection electrical measurements require Instrument resolution;...
Page 484 KCl calomel electrodes are available, positive side of the circuit. When connected in this manner, though modifications may be necessary to increase contact an analog instrument needle moves in an upscale area with the environment. NACE International...
Page 485 (see Figure 1a). This negative pipe-to- welding equipment, foreign rectifier, mining equipment, and electrolyte potential is the value used for NACE criteria. electric railway or transit systems; (n) Contacts with other metals or structures; 5.6.2 Pipe-to-electrolyte potential measurements are...
Page 486 Pipe Figure 1a Instrument Connection 0.850 Voltmeter Direction of meter current VOLT Reference Electrode Electrode potential does not vary Pipe Test Lead Pipe potential is the variable Pipe Figure 1b Alternative Instrument Connection FIGURE 1 Instrument Connections NACE International...
Page 487 6.1.8 Cathodic protection current-carrying conductor the potential being measured; used as a test lead for a pipe potential measurement. Electrolyte between pipe and disbonded coating causing error due to electrode placement in electrolyte on opposite side of coating; NACE International...
Page 488 (see Figure 2a). Conversely, the potential is less a pipe-to-electrolyte potential free of voltage drop is negative by that amount if the pipe current direction is NACE International...
Page 489 PIPELINE CURRENT SUBTRACT PIPE METAL VOLTAGE DROP FROM PIPE-TO-ELECTROLYTE MEASUREMENT WHEN CURRENT IS AWAY FROM PIPE CONTACT Figure 2b Correction When Pipeline Current Flows Away from Pipe Test Connection FIGURE 2 Pipe-to-Electrolyte Potential Corrections for Pipeline Current Flow NACE International...
Page 490 (a) Potential measured includes voltage drops other adequacy of cathodic protection on a steel or cast iron than those across the pipe metal/electrolyte interface; pipeline according to the criterion stated in NACE Standard RP0169, Paragraph 6.2.2.1.1: (b) Meeting the requirements for considering the significance of voltage drops (see Paragraph 8.6) can...
Page 491 NACE Standard RP0169, Paragraph 6.2.2.1.2: 9.3.4 Current sources that can affect the accuracy of this test method include the following: A negative polarized potential of at least 850 mV...
Page 492 Time should be allowed for the pipeline cathodic protection system parameters have changed. potentials to reach polarized values. 9.6.2 Install place operation necessary interrupter equipment in all significant DC sources NACE International...
Page 493 (for example, 500 criterion stated in NACE Standard RP0169, Paragraph mV or less negative) and/or the current required to 6.2.2.1.3, 6.2.3.1, or 6.2.4.1 (depending on the pipe meet a negative 850 mV polarized potential metal).
Page 494 "Instant Off" Potential (Polarized Potential) Polarization Decay Depolarizing Line Spike Figure 3a Polarization Decay 1,200 Current Interruption 1,100 Polarizing Line Normal Operation "On" Potential 1,000 "Instant-Off" Potential Polarization Cathodic Protection Applied Corrosion Potential Figure 3b Polarization Formation FIGURE 3 Cathodic Polarization Curves NACE International...
Page 495 10.2.5.5 Connect the voltmeter to the pipeline and protection at a test site on steel, cast iron, aluminum, or reference electrode as described in Paragraph copper piping according to the criteria stated in NACE 5.6. Standard RP0169, Paragraphs 6.2.2.1.3, 6.2.3.1, or 6.2.4.1 (depending on the pipe metal).
Page 496 100,000 ohms per volt may be adequate in certain circumstances in which the circuit resistance is 10.3.5.6 Apply the cathodic protection current. low. A potentiometer circuit may be necessary in Time should be allowed for the pipeline potentials other instances. to reach polarized values. NACE International...
Page 497 ________________________________________________________________________ References F.J. Ansuini, J.R. Dimond, “Factors Affecting the NACE Standard RP0169 (latest revision), “Control of Accuracy of Reference Electrodes,” MP 33, 11 (1994), p. External Corrosion on Underground or Submerged Metallic Piping Systems” (Houston, TX: NACE). NACE Publication 35201 (latest revision), “Technical NACE Standard RP0177 (latest revision), “Mitigation of...
Page 498 TM0497-2002 NACE Publication 35201 (latest revision). “Technical Report Parker, M.E. Pipeline Corrosion and Cathodic Protection. on the Application and Interpretation of Data from 2nd ed. Houston, TX: Gulf Publishing, 1962. External Coupons Used Evaluation Cathodically Protected Metallic Structures.” Houston, Stephens, R.W. “Surface Potential Survey Procedure and TX: NACE, 2001.
Page 499 ________________________________________________________________________ Appendix B: Net Protective Current B1 NACE Standard RP0169, Paragraph 6.2.2.2.1, states tests should be made on both sides of the pipe to that measuring the net protective current from the verify that current is leaving the line.
Page 500 (When the polarity of the measured value changes again, a possibly cathodic condition is indicated.) (See B3.11.2 The reference electrode is left in the same Figure B1.) location and is connected to the negative terminal of the voltmeter. A second reference electrode is NACE International...
Page 501 B4 Data Interpretation: source of the peaks. Pipe-to-electrolyte (or electrode- to-electrode) potential measurements should be made NACE International...
Page 502 B6.2 It is necessary to wait until polarization has stabilized before making a detailed evaluation of the net current protective level. Polarization of bare pipe may require a relatively long time ranging up to several months. NACE International...
Page 503 NOTE: Actual readings are usually 50 mV or less. As the anodic condition in the center of the figure is passed (traveling left to right), the indicated polarity switches from positive to negative. This polarity reversal indicates an anodic condition. FIGURE B1 Surface Potential Survey NACE International...
Page 504 Reference Electrode Intervals for Potential Survey Using Moving Meter and Wire Reel. CATHODIC PROTECTION NOT APPLIED AREAS EXPERIENCING CORROSION -700 -600 -500 -400 Linear Distance Figure B2c Variation of Pipe-to-Electrolyte Potential with Survey Distance FIGURE B2 Pipe-to-Electrolyte Potential Survey of a Noncathodically Protected Pipeline NACE International...
Page 505 See NACE Publication 35201 more information on coupon use. The following test C2.2.3 The significance of voltage drops due to procedures are suggested as guides.
Page 506 Location of a known or suspected corrosive pipeline according to the criteria stated in NACE environment. Standard RP0169, Paragraphs 6.2.2.1.3, 6.2.3.1, or 6.2.4.1 (depending on the pipe metal).
Page 507 C3.4.2 Two color-coded meter leads with clips for potential and its polarity with respect to the connection to the coupon and reference electrode. reference electrode. C3.4.3 Reference electrode C3.5.8 Leave the coupon test lead disconnected to allow the coupon to depolarize. C3.4.3.1 CSE. NACE International...
Page 508 When at least 100 mV or more of polarization decay measured with respect to a standard reference has been measured, the pipeline “on” potential at the test site may be used for monitoring unless significant environmental, structural, coating integrity, or cathodic protection system parameters have changed. NACE International...
Page 509 Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent.
Page 510 STG 35 on Pipelines, Tanks, and Well Casings. In NACE standards, the terms shall , must , should , and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual , 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements.
Page 511 TM0101-2001 ________________________________________________________________________ NACE International Standard Test Method Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Tank Systems Contents 1. General ........................... 1 2. Definitions ........................1 3. Safety Considerations ..................... 3 4. Instrumentation and Measurement Guidelines ............... 3 5.
Page 512 Definitions in this section reflect common usage among practicing corrosion-control personnel and apply specifically to how terms are used in this standard. As much as possible, these definitions are in accord with those in the “NACE International Glossary of Corrosion-Related Terms.”...
Page 513 Potential Gradient: A change in the potential with respect to distance, expressed in mV per unit of distance. NACE International...
Page 514 Inspections include shoring the test leads. Refer to NACE Standard RP0177 requirements for excavations and testing for hazardous additional information about electrical safety. atmospheres in confined spaces. 3.1.3 Use caution when making tests at electrical 3.1.7 Observe...
Page 515 For an analog instrument, negative terminal of the voltmeter, and the red lead is the voltage measurement is more accurate when it is connected to the positive terminal. measured in the upper two-thirds of a range selected for a particular instrument. NACE International...
Page 516 Note: A high-input impedance (>10 megohm) voltmeter or potentiometer voltmeter should be used to eliminate the 5.6 Meter Polarity effects of Paragraph 5.7, (a), (b), (c), (f), and (g) on the potential measurement 5.6.1 Tank-to-electrolyte potentials often measured by connecting the negative terminal of the NACE International...
Page 517 VOLT Reference Electrode Electrode potential does not vary does not vary. Pipe Test Lead Tank Test Lead Tank potential Pipe potential is the variable. is the variable Pipe Tank Figure 1b Alternative Instrument Connection Figure 1 Instrument Connections NACE International...
Page 518 5.12 The effect of voltage drops on a tank-to-electrolyte cathodic protection device. potential measurement can be determined by interrupting NACE International...
Page 519 6.2.3 Frozen soil: Contact resistance may be reduced and the reference electrode location. (Section 11 by removing the frozen soil to permit electrode contact provides guidance on methods of troubleshooting that with unfrozen soil. identify continuity or discontinuity.) NACE International...
Page 520 Section 8: Test Method 1—Negative 850-mV Tank-to-Electrolyte Potential of Steel Tanks with Cathodic Protection Applied 8.1 This section describes the most commonly used test interpretation this voltage method to satisfy the criterion stated in NACE Standard measurement.” RP0285: 8.1.1 “Consideration” is understood to mean the “A negative (cathodic) potential of at application...
Page 521 Color- 8.6 Evaluation of Data coded meter leads are suggested to avoid confusion of polarity for the measured value. 8.6.1 The significance of voltage drops can be considered by comparing historical levels of cathodic NACE International...
Page 522 9.3.1 Advantages measurement for comparison with the criterion stated in NACE Standard RP0285: (a) Voltage drops associated with the protective currents being interrupted are eliminated. “A negative polarized potential of at least 850 mV relative to a saturated 9.3.2 Disadvantages...
Page 523 NACE Standard test site according to the 100-mV criterion. Consequently, RP0285...
Page 524 10.2.4.1.1 Recording voltmeters can be useful for recording polarization decay. 10.2.5.6 Connect the voltmeter to the tank and reference electrode as described in Paragraph 5.6. NACE International...
Page 525 NACE Standard unnecessarily extended period. RP0285: 10.2.5.8.2 If extended polarization decay time “The following criterion shall...
Page 526 Polarization Decay 1,200 Current Interruption 1,100 Polarizing Line Normal Operation "On" Potential 1,000 "Instant-Off" Potential Polarization Cathodic Protection Applied Corrosion Potential Time Period (May be seconds, minutes, hours, or days Figure 2b Polarization Formation FIGURE 2 Cathodic Polarization Curves NACE International...
Page 527 10.3.5.7 Apply the cathodic protection current. terminal connections suitable for making reliable Sufficient time should be allowed for the tank electrical contact with the tank and reference potentials to reach polarized values. electrode. Color-coded meter leads are suggested NACE International...
Page 528 11.3.2.4 Disconnect the test lead from the tank electrolyte potential comparison measurements. and continue to test other structures by connecting that lead to the structure in question. 11.3.2 The following procedure shall be followed when testing for continuity using the fixed cell/moving ground technique: NACE International...
Page 529 This test can also be used to confirm the fixed cell/moving ground and potential difference technique test results. NACE International...
Page 530 Techniques Related to Criteria for Cathodic Protection of Protection” (Houston, TX: NACE). Underground or Submerged Steel Piping Systems (as defined in NACE Standard RP0169-83)” (Houston, TX: NACE Standard RP0177 (latest revision), “Mitigation of NACE). Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems”...
Page 531 “Potential Measurements for Determining NACE/CEA Report. “Cathodic Protection Monitoring for Cathodic Protection Requirements.” Corrosion 7, Buried Pipelines.” Houston, TX: NACE, 1990. 12 (1951): pp. 410-418. Peabody, A.W. Control of Pipeline Corrosion. Houston, Gummow, R.A. “Cathodic Protection Potential Criterion for TX: NACE, 2001.
Page 532 (a) Of the same material and with the same or nearly the to assess the adequacy of cathodic protection on a same properties as the tank; steel tank according to the criterion stated in NACE (b) Known not to interfere with determining the adequacy Standard RP0285: of the cathodic protection system;...
Page 533 A.6.3.3.1 Record the location of the electrode protection on a steel tank according to the criterion to allow it to be returned to the same location stated in NACE Standard RP0285, as follows: for subsequent tests. “The following criterion shall apply: A A.6.3.4 Connect the voltmeter to the coupon test...
Page 534 Continue to measure and record the coupon-to-electrolyte potential until it either: (a) Has become at least 100 mV less negative than the instant-off potential; or (b) Has reached a stable depolarized level. NACE International...
Page 535 TM0101-2001 ISBN 1-57590-137-4 NACE International...

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