What conditions promote galvanic corrosion?

• A. Purely dry contact of metals
• B. Absence of electrolyte
• C. Two dissimilar metals in electrical contact in an electrolyte
• D. The metals are same alloy

Answer: (C)

Galvanic corrosion happens when two dissimilar metals are in electrical contact and an electrolyte is present. The electrolyte allows ions to move and completes the electrochemical circuit. Because the metals have different electrochemical potentials, one becomes the anode and corrodes, while the other acts as the cathode and is protected. This combination is why two different metals in contact in a wet or damp environment (especially with salts) corrodes more quickly.

If there’s no electrolyte (dry contact), there’s little to no ionic conduction, so the galvanic reaction doesn’t proceed. If the metals are the same alloy, there’s no potential difference to drive a galvanic cell.