Effect of Polythionic Acid Concentration on Stress Corrosion Cracking of Sensitized 304 Austenitic Stainless Steel

Stress corrosion tests using U-bend specimens were carried out in Samans solutions containing polythionic acid concentrations from 0.03 moles/liter to 0.38 moles/liter. Results reveal that the stress corrosion life decreases rapidly on increasing the concentration from 0.03 to 0.18 moles/liter, but a further increase up to 0.38 moles/liter had a small effect. Stress corrosion tests were also carried out in individual thionic acid solutions in order to identify the chemical species causing SCC. The chemical analysis of the test solutions both prior to and subsequent to stress corrosion tests were also carried out. Some model tests were performed in order to ascertain the role of oxygen on SCC. The study of the change in corrosion potential with respect to time during stress corrosion tests suggest a potential range from −36 to −86 mV in which cracking occurs.