Abstract
The effect of Ni content and temperature on corrosion behaviour of stainless steels in highly concentrated sulfuric acid was studied by electrochemical methods. Corrosion rate of stainless steels in highly concentrated sulfuric acid decreased as Ni content increased in low temperature region less than 60°C. Inversely, the corrosion rate increased in proportional to the increase of Ni content in the high temperature region over 60°C. The main cause of the above phenomena was considered to be that the dissolution rate of stainless steels in the activepassive transition range was accelerated by the rapid increase of the frequency of potential oscillation in high temperature region. It was also clarified that the cathodic reaction of molecular sulfuric acid resulting in the formation of water (H2O) and elemental sulfur (S°), easily occured on passivated metal surface of Ni bearing stainless steels, and subsequently led to the corrosion potential to less-noble state by the dissolution of passivated film with the water, which accelerated the frequency of potential oscillation and increased corrosion rate of stainless steels with Ni content in high temperature region.
