Influence of Cathodic Protective Currents on Ship-Bottom Paints

Abstract

Authors investigated some phenomena of paint-film blisters on ship bottom hulls, and obtained experimental data about these blister formations and their characteristics. From these results, we recognized that cathodic currents might produce paint-film failures. So, we experimented various marine tests for several paints and painting systems with cathodic protection. Results of our investigation are as follows: (1)Proper cathodic potential for oil-base paint-films was -900mV, and -1,000mV for vinyl-resin base paint-films (refered to Cu/CuSO_4 electrode). (2)Cathodic current dnsities for active ships would require 10∼15 mA/m^2. (3)Millscale on hull-plates should be removed, and good results were not obtained from our experiments on Bituminous paint systems. (4)Anti-fouling action of A/F paints was not effected by protective currents in actual sea water immersion tests.