Metals Galvanic Compatibility Chart - Elna Magnetics
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Metals Galvanic Compatibility Chart
Leader Tech Copper Beryllium gaskets are non-porous, non-hygroscopic, and have a smooth surface. Properly
applied, wiping gaskets are inherently self-cleaning and resist oxidation given the absence of moisture.
Compression-only gaskets usually have high-pressure contacts, which bind the two surfaces and resists oxidation.
However, given enough time, temperature, and other environmental effects all of the metals we use will corrode.
In the presence of oxygen, metals oxidize. Other atmospheric effects and thermal cycling accelerates this pro-
cess. When moisture is present, these oxidized salts form electrolytes between the two dissimilar metals and
become a simple battery. As currents flow from the cathode to the anode, voltage potentials develop. The voltage
amplitude is directly proportional to currents flowing across the junction of the two metals. These currents accelerate
corrosion of the metals.
Using Mil-STD 1250, the galvanic potential should not exceed .25 volts. This specification is critical for salt
spray or other harsh environments. In commercial applications, many engineers allow up to .5 volts in controlled
environments. To reduce the effects of galvanic conditions, we suggest using the following chart to select the
correct metals and plating surfaces.
Anode
Cathode
Zinc
0.50
Aluminum
0.83
0.33
Cadmium
0.80
0.30
0.02
Tin
1.10
0.60
0.28
0.30
Iron, Steel
0.90
0.40
0.08
0.10
0.20
Chromium
1.15
0.65
0.33
0.35
0.05
0.25
Brass
1.35
0.85
0.53
0.55
0.25
0.45
0.20
Copper, Bronze
1.35
0.85
0.53
0.55
0.25
0.45
0.20
Nickel, Monel
1.45
0.95
0.63
0.65
0.35
0.55
0.30
0.10
0.10
Stainless Steel
1.40
0.90
0.58
0.60
0.30
0.50
0.25
0.05
0.05
0.05
Silver
1.60
1.10
0.78
0.80
0.50
0.70
0.45
0.25
0.25
0.15
0.20
1. For units which will be subjected to salt spray or salt water, metal should be chosen where the potential difference is less than 0.25V.
2. Where it is possible the unit will be subjected to high humidity that is not salt laden, then the potential difference should not exceed 0.45V.
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