Influence of Concentration of H2SO4 and NaCl on Stress Corrosion Cracking in H2SO4-NaCl Solutions

Abstract

An SCC test was carried out in aqueous solutions containing both H 2 SO 4 (0～5.5 kmol/m 3 ) and NaCl(0～4.5 kmol/m 3 ) as solutes, in order to study the influence of the environment on the corrosion type of an SUS304 steel. The both solutes of H 2 SO 4 and NaCl have synergistic influence on the corrosion type, and SCC occurs within a specific concentration region and general corrosion occurs at the other concentrations. For a constant H 2 SO 4 concentration the corrosion mass loss decreases with increasing NaCl concentration up to a certain value and then increases. This tendency makes a V shape curve when the mass loss is plotted against the NaCl concentration. On the other hand, SCC crack length increases with increasing NaCl concentration up to a certain value, passes a maximum, and then decreases. This tendency is just like an inverse V shape curve. In addition, the NaCl concentration ranges for the minimum mass loss and maximum crack length are almost equal. It was also confirmed that these NaCl concentration regions are inversely proportional to the H 2 SO 4 concentration.