Which of the following is a method which interferes with the flow of the current in the electrochemical cell?

• A. Anodic protection
• B. Cathodic protection
• C. Surface coating
• D. Heat treatment

Answer: (B)

Cathodic protection controls where the electrochemical current flows by making the protected metal act as a cathode. When a structure is cathodically protected, it is supplied with electrons (from sacrificial anodes or an external source) so its surface sits at a more negative potential. This suppresses the anodic dissolution that drives corrosion and redirects the current in the external circuit away from promoting metal loss. In other words, the corrosion current is inhibited because the metal no longer acts as an anode; its surface undergoes reduction instead of oxidation. Anodic protection would push the metal to become more anodic and worsen corrosion; surface coatings act mainly as a barrier to ion/electron transfer and don’t actively force the surface to be cathodic; heat treatment does not directly control electrochemical current flow.