Effects of electric current density and pipeline current on cathodic protection

To identify the distribution of cathodic protection current in long-distance pipeline, the cathodic protection parameters of two anticorrosive coatings (3PE and petroleum asphalt) at different cathodic protection station spacing are calculated with numerical simulation technique. Then, the relationship between and distribution of current density, pipeline current and pipeline resistance voltage drop are analyzed. On this basis, the pipeline On-Off potential and its IR drop are discussed. The research results show that approximately uniform protection can be achieved when the coating insulation performance parameters and pipeline cathodic protection station spacing parameters are matched, in other words, potential decay along the pipeline is small, and the current density is approximately uniform bulk flow to the pipeline, . In addition, pipeline resistance voltage drop formed by the pipeline current is a part of IR drop in pipe-to-soil potential measurements and On-Off potential measurements. It should be away from the pipeline power point when power method applied in the evaluation of anticorrosive coating insulation performance.