In order to investigate the influence of electrode coating materials on the reproducibility of the polarization curves of stainless steels, the anodic polarization curves of SUS 304 steel and 316 steel with various coating materials were measured in sulfuric acid solution. The results showed that the values of the critical passivation current density and corrosion potential of the steel were sometimes affected when certain materials were used as the coatings, and that the passive current density of the steel was little influenced by coatings. The values of icrit of the 304 steel in 5% sulfuric acid solution increased over ten times of the ordinary values and corrosion potential shifted about 100mV towards negative by use of some kinds of silicone sealant. The degree of the increase depended on not only the concentration of dissolved material (or materials) from the sealant, but also the reactivity of the extracted material. On the other hand, in the test for evaluating the current efficiency of sacrificial aluminum anodes the higher efficiency was evaluated errorneously by the use of a silicone sealant. Since the harmful action of this sealant differed with different products on the market in its power, it is necessary to check the product for having no influence on the measurement. It was presumed that the increase of icrit, together with the improvement of current efficiency would arise from the suppression of hydrogen evolution reaction by the sealant.
