Impressed Current Cathodic Protection

Cathodic protection can be also applied if the metal to be protected is coupled to the negative pole of a direct current (DC) source, while the positive pole is coupled to an auxiliary anode. Since the driving voltage is provided by the DC source there is no need for the anode to be more active than the structure to be protected. In fact, it is possible to use anodes which can remain inert (non consumable) during impressed cathodic protection. This type of anode supports other anodic reactions on their surfaces. In environments where water and chloride ions are present, chlorine evolution and oxidation of water are possible. It is also possible to use semi-consumable anodes such as graphite and high silicon iron or consumable anodes  such as scrap iron, for example.

All items to be protected shall be electrically connected and should have a welded or brazed connection to an anode. For bolted or clamped assemblies without an all welded brazed electrical grounding, the electric resistance should be less than 0.10 ohm. Coating on contact surfaces shall be removed prior to assembly.