Influences of Concentrations of H2SO4 and NaCl on Stress Corrosion Cracking of SUS304 Stainless Steel in H2SO4--NaCl Aqueous Solutions

A stress corrosion cracking (SCC) test was carried out at room temperature in aqueous solutions containing both H2SO4 (0-5.5 kmol.m^-3) and NaCl (0-4.5 kmol.m^-3), in order to study the influences of both solutes on the corrosion type of SUS304 steel. The two solutes have synergistic influence on the corrosion type, that is, SCC and general corrosion occur within a specific concentration range and elsewhere, respectively. For a constant H2SO4 concentration the mass loss of corrosion shows a V-shape when it is plotted against NaCl concentration. On the other hand, maximum crack length of the SCC increases with increasing NaCl concentration up to a certain value, and then decreases. This gives a nearly inverse V-shape curve. In addition, the NaCl concentration ranges for the minimum mass loss and for the maximum crack length are almost the same. It was also confirmed that NaCl concentrations showing the minimum mass loss and the maximum crack length are inversely proportional to H2SO4 concentrations.