A sacrificial anode used to control or reduce the effects of electrolysis is what material?

• A. A zinc
• B. A copper
• C. A magnesium
• D. A steel plate

Answer: (A)

This tests sacrificial protection against galvanic corrosion. You attach a metal that is more anodic than the structure you want to protect, so it corrodes first and sacrifices itself to spare the other metal. Zinc is used as the sacrificial material for steel in many environments because it is more electrochemically active than steel, so it will corrode instead of the protected metal. Copper is more noble and wouldn’t provide this protective effect, and a steel plate is the protected structure, not the sacrificial anode. Magnesium is even more active and is used in some specific situations, but zinc is the standard choice for many marine applications.