Cathodic Protection and Electrocoating on a Coated Steel Channel in Freshwater

Abstract

The cathodic protection by impressed current system was applied to a coated steel channel, which had been used for 40 years and leads river water to its filtering plant. The flowing rate of water was 1.8m/s. The formation of electrocoating on the damaged and corroded area of coating was examined. At the same time, the effect of the formed electrocoating on potential distribution and polarization behavior were studied. Cathodic current density was maintained at 10mA/m² for 143 days and at 25mA/m² for the following 140 days. When the impressed current density was 10mA/m², neither the potential nor its distribution was improved by time. Instead, at 25mA/m², the potential was moved toward the negative and the potential distribution became uniform. After the test, it was observed that electrocoating was formed not only on the surface of tubercles but also in their rust layers. The formation of effective electrocoating and the uniform potential distribution made the application of cathodic protection very feasible to this coated steel channel.