Cathodic Protection Design and Operation

Abstract

Cathodic protection has probably become the most widely used method for preventing the corrosion deterioration of metallic structures in contact with any forms of electrolytically conducting surface. The most rapid development of cathodic protection system was made in the United States of America to meet the requirement of the rapidly expanding oil and natural gas industry which wanted to benefit from the advantages of using thin-walled steel pipes for underground transmission. Cathodic protection can, in principle, be applied to any metallic structure in contact with bulk electrolyte. In practice its main use is to protect steel structures buried in soil or immersed in water. Structures commonly protected are the exterior surfaces of pipelines, ships, hulls, jetties, foundation piling and steel sheet-piling. Cathodic protection is also used on the interior surfaces of water-storage tanks and water circulating systems and the corrosion may occur inside the pipe due to its content. Cathodic protection has also been applied to steel embedded in concrete, to copper-based alloys in water system, and exceptionally, to lead-sheathed cables and aluminum alloys. Cathodic protection is a technique to reduce the corrosion of the metal surface by making that surface the cathode of an electrochemical cell. Cathodic protection may be achieved in either of two ways: by the use of an impressed current from an electrical source, or by the use of sacrificial anodes (galvanic action) or mixture of two systems.