Cathodic protection is a method which protects the metal reliably even at undetected coating holidays. The protective current supplies electrons to the structure which is protected. These electrons cover the electron requirements forthe reduction of oxygen which comes into contact with the metal surface

Without cathodicprotection, these electrons would 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.

cathodic reaction: ½O + H2O + 2e→2OH