Cathodic protection is a method which reliably protects the metal even at undetected coating holidays. The protective current supplies electrons to the structure which is protected. These electrons cover the electron requirements for the reduction of oxygen which comes into contact with the metal surface. Without cathodic protection, these electrons provide the decomposition of the metal. Thus, the potential of the metal surface is sufficiently reduced to prevent the disassociation of positive ions from the metal. Where formerly an anodic reaction took place, the oxygen is reduced by cathodic reaction. The entire surface of the structure protected is thus transformed into a safe cathode, i.e. the metal is " cathodically " protected.
