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ELECTROCHEMICAL CORROSION PREVENTION
Electrochemical potential differences between various materials
When installing and grounding lightning EMP protection devices, consideration shall be given to the electrochemical potential difference existing between the metallic housing parts of the device and the mounting walls or other fastening and contact elements.
According to MIL-F-14072, the magnitude of the potential difference should not exceed 250 mV in order to minimise possible electrochemical corrosion. The following table shows the associated potential differences of the most important metals and galvanically applied metal surfaces for the applications under consideration.
|
Magnitude of the electrochemical potential difference between different surface metals in V |
Gold |
Silver |
Nickel |
SUCOPLATE® and commercial alloys of copper |
Stainless steel |
Chromium |
Tin |
Aluminium |
|
Gold |
0.00 |
0.15 |
0.30 |
0.40 |
0.50 |
0.60 |
0.65 |
0.75 |
|
Silver |
0.15 |
0.00 |
0.15 |
0.25 |
0.35 |
0.45 |
0.50 |
0.60 |
|
Nickel |
0.30 |
0.15 |
0.00 |
0.10 |
0.20 |
0.30 |
0.35 |
0.45 |
|
SUCOPLATE® and commercial alloys of copper |
0.40 |
0.25 |
0.10 |
0.00 |
0.10 |
0.20 |
0.25 |
0.35 |
|
Stainless steel |
0.50 |
0.35 |
0.20 |
0.10 |
0.00 |
0.10 |
0.15 |
0.25 |
|
Chromium |
0.60 |
0.45 |
0.30 |
0.20 |
0.10 |
0.00 |
0.05 |
0.15 |
|
Tin |
0.65 |
0.50 |
0.35 |
0.25 |
0.15 |
0.05 |
0.00 |
0.10 |
|
Aluminium |
0.75 |
0.60 |
0.45 |
0.35 |
0.25 |
0.15 |
0.10 |
0.00 |
Important
The classification according to ASTM D1141-90 conforms to MIL-F-14072 and has proved convenient for contacting metals in electronics. It shall not be confused with the academic consideration of chemistry textbooks. The tables shown there refer to a gas reference electrode and a salt solution of the specimen metal between the electrodes.
