Anodic Protection Method for Stainless Steel in Contact with Noble Metals in the Concentrated Sulfuric Acid Environment

摘要

It is known that the stainless steel (SS) like the type 316 SS shows cyclic oscillation of the corrosion potential in the concentrated and the medium temperature sulfuric acid solution environment. With this potential oscillation, the stainless steel suffers the general corrosion. This general corrosion of the type 316 SS is not permitted in some process for the problem of the contamination and the productivity.The authors have studied the prevention method of this general corrosion. It has been found that the anodic protection method, where the noble metals such as gold and platinum come in contact with the type 316 SS, is effective. This anodic protection method has been successfully applied to the actual process environment using the concentrated sulfuric acid. It is considered that the small cathodic over voltage of the noble metal compared to the SS is due to the catalytic reducing reaction of the molecular sulfuric acid on the surface of the noble metal.