Investigation of local cathodic protection of carbon steel pipe by immersed current method

The cathodic protection (CP) is widely used in the oil and gas industry to prevent (or reduce) corrosion of structures and metal pipelines. To guarantee a more effective CP system, an applicable design for the under-protected structures is required. The potential decay on steel structure surface, due to being away from the power source, can cause a considerable local protection deficiency of parts of the structure due to the enhanced corrosion attack. In the present work, the local cathodic protection of carbon steel pipe in different concentrations (0.01 N,0,05 N, 0.1N) of NaCl solutions in was investigated and discussed. Quantitative values of the effect of potential decay on the protection efficiency and on the immersed current were reported under different operating conditions such as anode to cathode area ratio, anode to cathode distance. The use high area ratio of graphite to CS structure, gave high protection percent reaching up to 100% even for the pipe’s portion that is far from the connection point with the anode.