1997 Volume 46 Issue 8 Pages 481-490
Microbially influenced corrosion (MIC) behavior of stainless steels in natural Seawater, the accelerated corrosion test method and the countermeasure to MIC were studied. Electrochemical measurements and immersion tests were carried out. Furthermore, the effect of the surface. treatment of a stainless steel on the MIC resistance was studied Susceptibilities to localized corrosion of stainless steels in natural seawater are higher than those in synthetic seawater. The biofilm formed on the surface of stainless steels in natural Seawater contains the activated oxygen such as peroxide generated by the metabolism of aerobic bacteria. The corrosion potential becomes noble in the presence of the peroxide because of its higher redox potential than that of oxygen. The ennoblement of corrosion potential can be reproduced in the laboratory by the addition of oxidase to simulate the metabolism of aerobic bacteria. This method can be used to evaluate the MIC resistance of various materials in the laboratory. The surface film of stainless steels electrolyzed in the Fe (III) and Cr (VI) containing solution is the bipolar membrane which consists of the anion selective membrane in the outer layer and the cation selective membrane in the inner layer. This bipolar membrane suppresses the catholic reaction, therefore, the corrosion potential does not become noble even in the presence of the activated oxygen generated by the aerobic bacterial metabolisms, and leads to the improvement of the MIC resistance.
