Effect of Sensitization on Stress Corrosion Cracking of Type 316 Austenitic Stainless Steel in Sulfuric Acid Solution

Abstract

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as functions of applied stress, sensitizing temperature and sensitizing time in 0.82 kmol/m3 sulphuric acid solution by using a constant load method. The applied stress dependence of the three parameters (lss, steady state elongation rate, tss, transition time, tf , time to failure) showed three regions irrespective of sensitizing temperature and sensitizing time; the stress- dominated, SCC- dominated and corrosion- dominated regions. In the SCC- dominated region, the logarithm of lss was a linear function of the logarithm of tf for each sensitized specimens, showing that lss became a relevant parameter for prediction of tf, although the slope depended upon sensitizing temperature and sensitizing time. At a sensitizing time of more than 360 ks, the SCC susceptibility was found to reduce because of Cr healing. Sulphate ions became more aggressive to SCC than chloride ions for the specimens with the severest sensitization. The effect of sensitization on SCC and the role of sulphate ions were discussed and further a qualitative IGSCC mechanism was proposed.