Cathodic Protection

Cathodic protection systems prevent the oxidation / corrosion process from occurring in a metal body by creating a current flow from the cathodic protection system to the structure being protected. There are two basic types of CP systems: galvanic and impressed current.

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In a galvanic Cathodic Protection system, the anodes connected to the protected structure have a natural potential that is more negative than the structure’s. When connected current flows from the anode (more negative potential) to the structure (less negative potential) in a DC circuit. Therefore in this process, the "sacrificial metal" with higher negative potential will sacrifice itself (corrode faster), which helps the metal being protected to stay unaffected by the corrosion process. These galvanic anodes can be used to protect underground steel, marine, internal and industrial structures from corrosion. They do not require an outside power source to operate and are therefore limited in their use.

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In many situations, the potential difference between the galvanic (sacrificial) anode and the steel structure needing protection from corrosion, is not enough to generate sufficient current to enable the anode from sacrificing itself which can the offer the required cathodic protection. In these cases, a power supply (rectifier) is used to generate larger potential differences that enables more current to flow to the structure being protected therefore offering cathode protection. This is referred to as an impressed current cathodic protection system.