What happens to the anode when cathodic protection is applied?

When cathodic protection is applied, the main focus is on the behavior of the anode within the system. In cathodic protection systems, especially those using sacrificial anodes, the anode material is intentionally made to corrode more readily than the metal structure being protected. This process involves the anode becoming less reactive as it sacrifices itself to prevent corrosion of the cathode.

In the context of the question, the anode does not become more acidic as a direct result of cathodic protection; instead, its function is to provide electrons that reduce the potential of the cathodically protected structure and control the electrochemical environment. While an increase in acidity may alter corrosion rates, it does not directly characterize what happens to the anode in cathodic protection systems.

The correct response indicates that the reactivity of the anode decreases because it is corroding in a controlled manner to protect another metal. This helps maintain the integrity of the structure being protected from corrosion by creating a balance in the electrochemical reactions that occur.