– This work aimed to study the effect of environment resistivity and distance between cathode and anode on the required cathodic protection current density of buried carbon steel pipes and determine the impressed current that gives full protection to bare and coated pipes by two different coatings.
– The experimental apparatus is an electrochemical cell composed of carbon steel pipe of 10 cm in length as a working electrode in addition to reference and auxiliary electrodes and direct current power supply. The cathodic protection tests were carried out in five solutions of different concentrations of sodium chloride and distilled water with different resistivities.
– It was found that the cathodic protection current density increased with a decrease in environment resistivity and increase in the distance between cathode and anode. Additionally, the cathodic protection current density of coated pipes by two different polymers increased with a decrease in the environment resistivity and increasing number of coating defects.
– icp = D/A + B?2, where: icp = cathodic protection current density; D = distance between anode and cathode; ? = environment resistivity; A = constant (0.2104); and B = constant (0.864 × 10−6).
