Requirements On The Coolant; Table 15: Electrochemical Voltage Series / Standard Potentials Against Hydrogen; Table 16: Requirements On The Coolant - KEB COMBIVERT H6 Instructions For Use Manual

INSTALLATION Of WATER-cOOLED UNITS
Material Generated Ion
Aluminium Al
Manganese Mn
Zinc Zn
Chrome Cr
Iron Fe
Cadmium Cd
Table 15: Electrochemical voltage series / standard potentials against hydrogen

6.1.3 Requirements on the coolant

The requirements on the coolant are depending on the ambient conditions, as well as
from the used cooling system. General requirements on the coolant:
Standards
VGB
Cooling water directive
pH-value
Abrasive substances
Copper cuttings
Hard water
Soft water
Frost protection
Corrosion protection
Table 16: Requirements on the coolant
54
Standard
potential
-1.67 V
3+
-1.05 V
2+
-0.76 V
2+
-0.71 V
3+
-0.44 V
2+
-0.40 V
2+
TrinkwV 2001, DIN EN 12502 part 1-5, DIN 50930 part 6, DVGW work sheet W216
The VGB cooling water directive (VGB-R 455 P) contains instructions about com-
mon process technology of the cooling. Particularly the interactions between cool-
ing water and components of the cooling system are described.
Aluminum is particularly corroded by lixiviums and salts. The optimal pH value for
aluminum should be in the range of 7.5... 8.0.
Abrasive substances as used in abrasive (quartz sand), clogging the cooling circuit.
Copper cuttings can attach the aluminum and this leads to a galvanic corrosion.
Copper should not be used together with aluminum due to electro-chemical voltage
difference.
Cooling water may not cause scale deposits or loose excretions. It shall have a low
total hardness (<20°d) especially carbon hardness.
Soft water (<7°dH) corrodes the material.
An appropriate antifreeze must be used for applications when the heat sink or the
coolant is exposed temperatures below zero. Use only products of one manufac-
turer for a better compatibility with other additives.
Additives can be used as corrosion protection. In connection with frost protec-
tion the antifreeze must have a concentration of 20...25 Vol %, in order to avoid a
change of the additives.
Material Generated Ion
Copper Cu
Carbon C
2+
Silver Ag
Platinum Pt
Gold Au
Gold Au
Standard
potential
0.34 V
2+
0.74 V
0.80 V
+
1.20 V
2+
1.42 V
3+
1.69 V
+