Which condition promotes galvanic corrosion the most?

• A. Metals isolated from electrolyte
• B. Two metals with large potential difference connected in an electrolyte
• C. Only one metal present
• D. No moisture

Answer: (B)

Galvanic corrosion happens when two dissimilar metals are in electrical contact and share an electrolyte. The metal that is less noble (the anode) corrodes, while the more noble metal (the cathode) is protected. The driving force for this process is the potential difference between the metals—the larger the difference, the stronger the flow of electrons and the faster the corrosion of the anodic metal. An electrolyte is required to carry ions; without moisture there’s no path for ion movement, and with only one metal present there’s no galvanic pair to form a cell. So the condition that promotes galvanic corrosion the most is two metals with a large potential difference connected in an electrolyte.