Cathodic Protection is the utilization of the electrical properties of corrosion of metallic substances to provide a system for the protection of steel underground storage tanks (USTs), metallic piping or any other buried metallic structure, to extend their useful life. There are two types of cathodic protection: sacrificial anodes and impressed current.

 

Sacrifical anodes, also called galvanic cathodic protection system for USTs, consists of sacrificial anodes fixed to the UST during the manufacturing of the UST, and provides specified wiring for an inspection station installed near the surface of the ground. Galvanic systems have limited life spans during which the sacrificial anode will continue to degrade and protect the tank or piping. When the sacrificial anodes are no longer capable of protecting the tank or piping, they will lose their protection and begin to corrode.

 

The impressed current cathodic protection system usually provided anodes of a much longer life span than sacrificial anodes. These systems include a rectifier that converts the alternating current power source to a direct current, using the metal surface that is required protection as cathode, selecting specific material as supplementary anode, then the current is properly calibrated to provide the required protection. Since the power source is delivered to the electrodes and is not generated by the degradation of the electrode, the power supply to the electrode may be re-calibrated to provide additional power, when needed, as long as the electrodes are still functional. This technique has been widely recognized and applied in shipping industry, port facilities, ocean project, petrochemical, electric power, municipal pipes, and will have a more broad prospect.