Abstract
We have attempted to apply cathodic protection to steel in the atmosphere by employing a newly developed paint system comprising steel, a layer of insulating coating, a layer of conductive coating containing carbon powder, and a layer of insulating finish. Coastal industrial area exposure tests were conducted in Chiba, Japan. The percentage area of red rust in defects with applied potential was lower than in defects without applied potential. After two weeks the defects with applied potential were covered with a white film containing magnesium carbonate and the cathodic current had decreased. It is considered that the electro-deposited white film enhanced the anti-corrosive protection of the defects. It was demonstrated that measured cathodic current density through the defects conformed to the distributed parameter circuit model, assuming that electrolyte film or white film on a defect is a homogeneous and consecutive resistance film. From this model, we can deduce that a severely corrosive environment enhances the corrosion prevention effects of the newly developed paint system.
