- The surface ratio between the two metals: the least favourable case is that of a large cathodic surface (the most positive metal) electrically connected to a small anodic surface (the most negative metal). The corrosion rate of the most negative metal can be multiplied by 100, or even 1000. An assembly consisting of sheets of iron held by copper rivets is far more resistant to corrosion than the opposite set-up (copper sheets and iron rivets).
- The conductivity of the corrosive environment influences the location of deterioration. Galvanic corrosion can occur even in very resistant environments. In such cases, it happens at the point where the two metals touch. Conversely, the attack is located less in the conductive environment.
- The corrosion resistance of the most noble metal- regardless of its potential - has considerable influence on the behaviour of bimetallic torque. If the noblest metal corrodes, its corrosion products risk, through their movement, accelerating the corrosion of the most corrodible metal. For example, the products of copper corrosion can corrode aluminium. The result is that the copper-aluminium pair (which has a lesser difference in potential than the gold-aluminium pair) is, however more dangerous – because gold, which is incorrodible, does not present this risk.
A few ways of fighting against this corrosion: choose metallic pairs in which the elements are as close as possible in the table opposite; avoid an unfavourable surface relationship; avoid, as far as possible, direct contact between two different materials (by using a seal, insulator, coating, etc.).