In a galvanic pair of steel and copper in seawater, which metal is the anode and what is the consequence?

• A. Copper is the anode and corrodes faster; steel acts as the cathode.
• B. Both metals corrode at the same rate.
• C. Steel is the anode and corrodes faster while copper acts as the cathode; mitigation may involve CP adjustments or isolation to prevent galvanic current flow.
• D. The pair will not galvanically influence each other in seawater.

Answer: (C)

In seawater, galvanic corrosion happens when two dissimilar metals are in electrical contact and an electrolyte is present. The metal that is more active becomes the anode and dissolves faster, while the more noble metal acts as the cathode and is protected. Steel is the more active metal here, so it serves as the anode and corrodes faster; copper becomes the cathode and is relatively protected. The consequence is accelerated steel loss at the interface, which can compromise structure if not managed. To mitigate, adjust cathodic protection to make the steel more cathodic or isolate the metals with a barrier to stop galvanic current flow.