Cathodic protection(CP) is used to prevent corrosion of a metal surface. The metal surface forms the cathode, which, together with an anode placed in the ground or in another conductive medium, forms an electrochemical cell.
In cathodic protection, the anode may have a lower electrochemical potential than the cathode. It is then more susceptible to corrosion than the cathode, so that the current causing corrosion flows from the anode rather than the cathode. Cathodic protection is used to protect against corrosion on boat hulls, underground storage tanks, water heaters, and steel water and fuel lines, among other applications.