Cathodic protection - A proven corrosion control means in immersed or buried pipelines in oil,natural gas and Petrochemical Industries

Abstract

Cathodic protection (CP) is an electrochemical means of corrosion control in which the oxidation reaction in a galvanic cell is concentrated at the anode and suppresses corrosion of the cathode in the same cell. In cathodic protection, the object to be protected is the cathode. Cathodic protection can, in principle, be applied to any metal. In practice, cathodic protection is primarily used on carbon stecl. The effectiveness of CP allows carbon steel, which has little natural corrosion rcsistance,to be used in such corrosive environments as sea water, acid soils, saltladen concrete, and many other corrosive environments. Virtually all modern immersed or buried pipelines carrying high pressure hydro carbon (natural gas and petroleum products) are coated with an organic protective coating that is supplemented by cathodic protection systems to prevent corrosion at holidays in the protective coating. This combination of protective coating and CP is used on virtually all immersed or buried carbon steel structures, with the exception of offshore petroleum production platforms and reinforced concrete structures. Off shore platforms are usually uncoated but cathodically protected. Concrete structures normally rely on the protectiveness of the concrete cover to prevent the corrosion of embedded steel. When corrosion of embedded steel occurs because of a loss of this protectiveness,CP is sometimes used to extend the life of the already deteriorated structurc. This paper reviews development in cathodic protection of underground pipeline in the new millennium in oil, natural gas and petrochemical industries