Effects of S Content and Surface Finish on Pitting Corrosion of Austenitic Stainless Steels Containing Mo in Chloride and Bromide Solutions

Abstract

Pitting corrosion behavior of austenitic stainless steels with Mo was investigated in chloride and bromide solutions. The steels with higher S content as 0.009 mass% showed higher pitting potential in 1 kmol/m³ bromide solution than 1 kmol/m³ chloride solution. On the other hand, the steels with lower S content as 0.0003 mass% showed opposite results. The higher pitting potential was observed in chloride solution. This tendency became profound with passivation treatment by nitric acid. From the experimental results above, it is highly believed that chloride ions are more detrimental to sulfide inclusions induced pitting than bromide ions, whereas pitting due to breakdown of passive film other than sulfide inclusion is more easily caused in solutions containing bromide ions than chloride ions.