Measuring Half-Cell Potential; Before You Start; Procedure - Elcometer 331 Series Operating Instructions Manual

8 MEASURING HALF-CELL POTENTIAL

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Your Covermeter is capable of measuring half-cell potential - an electrochemical technique
commonly used to assess the severity of corrosion in reinforced concrete structures. When set to
half-cell mode, your Covermeter acts as a voltmeter which measures the potential difference
between the steel reinforcement in the concrete structure and a reference electrode (the half-cell)
placed on the surface of the concrete.
Half-cell readings can be stored in memory in batches in the same way as readings of cover.

8.1 Before you start

• Are you using the correct half-cell probe?
See "Half-cell probes" on page 28.

8.2 Procedure

1. Use the Covermeter to locate a reinforcing bar.
2. Expose the bar, e.g. by drilling through the cover using a large drill.
3. Drill a small diameter hole into the bar suitable for attachment of the positive (red) cable using
a screw or lead plug.
4. Mark out a grid on the concrete. Measurements will be taken at the intersection points of the
grid. Typical grid spacing is 1 m x 1 m, however this may be reduced if localised corrosion is
suspected. If the measured half-cell potential between two adjacent positions differs by more
than 100 mV, it is recommended that the grid spacing is reduced.
5. If necessary, use tap water to wet the whole of the test area, or just the measurement
positions.
6. Connect the red cable and extension reel between the exposed reinforcing bar and the red
terminal on the Covermeter (Figure 14). Connect the black cable between the probe and the
black terminal on the Covermeter.
7. Switch on the Covermeter.
8. Ensure the instrument is set to Half-cell mode
MENU / INSTRUMENT MODE / HALFCELL
9. Remove the end cap from the probe and store the cap safely.
10. Press the electrode against the concrete surface.
11. View the reading of half-cell potential on the display.
12. If you are satisfied with the reading, record the half-cell potential and then move on to the next
measurement location.
p. Half-cell mode is not included on the Elcometer 331 Model B.
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EASURING HALF CELL POTENTIAL
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