What is the cause of corrosion due to galvanic action?

Galvanic corrosion occurs when two different metals come into contact in the presence of an electrolyte, such as water. This electrochemical process happens because the dissimilar metals create a potential difference, leading to the more anodic metal corroding at a greater rate than it would if it were isolated. The metal that is more noble (cathodic) serves as a protective layer for the less noble (anodic) metal, which accelerates its corrosion.

When two unlike metals are in contact, the electrochemical properties differ, and this creates a galvanic cell. The less noble metal will corrode preferentially, while the more noble metal will remain relatively unharmed. Factors like the presence of moisture enhance this process as they act as an electrolyte, promoting the flow of ions necessary for the galvanic action.

In contrast, contact between two similar metals does not create a significant galvanic cell, and therefore, does not lead to this type of corrosion. High temperatures can affect the rate of corrosion and the effectiveness of barriers, but they are not a direct cause of galvanic action. While moisture is a contributing factor to corrosion generally, it is not the sole cause of galvanic corrosion, which specifically arises from the interaction of different metals