Stress Corrosion Cracking of 18-8 Austenitic Stainless Steel in Sulfuric Acid

Abstract

Weight loss and fracture time measurements of 18-8 stainless steel were performed with 4N H₂SO₄ solution containing sodium halides of various concentrations in the temperature range 25°C-98°C.
Crackings of the tensile specimens occurred within the temperature range 60°C-98°C in the acid solution containing chloride, bromide, or iodide, concentrations of which were about 2×10^-25×10^-1N, 10^-4-10-³N, or 5×10^-6-5×10^-5N respectively. The effect of temperature on the time to fracture caused in the chloride containing solution was identical with that in the iodide containing solution within the temperature range 45×C-98×C and was also identical with that in the bromide containing solution within the temperature range 60×C-80×C. In the acid solution with chloride, applied anodic current made the time to fracture shorter and cathodic current made it longer.
Although observed crackings were closely related to the inhibiting property of halogen ions, yet they may be not stress sorption cracking but stress corrosion cracking, where the halogen ions may act as passivating species on slightly deformed areas and as activating species on heavily deformed areas of the steel. Rate-termining mechanism of these crackings may not change in the temperature range 6×C-80×C.