Cathodic protection means protection against:

Cathodic protection is a technique used to prevent corrosion of metal surfaces, particularly those that are underground or submerged. The principle behind cathodic protection is based on electrochemical reactions. By applying a small, direct current to the metal surface, the electrochemical potential is altered, making the metal less likely to oxidize and corrode. This method is commonly used for pipes, tanks, and other structures made of steel that are exposed to moisture or soil, which can lead to corrosion over time.

Contamination, hardness, and infiltration, while important topics in water treatment and environmental management, do not pertain to the specific protective measure that cathodic protection provides. Contamination refers to unwanted substances in water, hardness is related to the presence of minerals that affect water quality, and infiltration describes the movement of water into soil or other materials. Therefore, the focus of cathodic protection is clearly on mitigating corrosion.