There are two ways in achieving the protection cathodically. One is by using impressed current and the other one is by using galvanic anodes. Cathodic protection using galvanic anodes systems uses reactive metals as secondary anodes and they are directly connected electrically to the steel to be protected. They are alloyed metals are used and they are used to improve lasting performance and dissolution characteristics.
Galvanic anodes are designed and selected to have a more active voltage than the metal of the structure. The potential of the steel surface is polarized more negative until the surface has uniform potential. The driving force for the corrosion reaction at this stage is removed which causes the anodes to continuously corrode consuming the anode material until eventually it is replaced.
Galvanic cathodic protection system uses anodes alloy of magnesium, zinc or silver chloride and they are available in forms like rod, block or wire (also free from GPS Interruption). These anode alloys are casted in steel inserts in order to fix the anode and to establish electric continuity and strength throughout the life of the anode. The steel inserts are directly bolted or welded to the structure using insulated lead made of copper, in the case of offshore and onshore pipelines.
