Stress Corrosion Cracking of AISI 304 and AISI 316 Austenitic Stainless Steels in HCl and H2SO4 Solutions — Prediction of Time-to-Failure and Criterion for Assessment of SCC Susceptibility

Abstract

The stress corrosion cracking (SCC) of AISI(1) 304 and AISI 316 austenitic stainless steels in 0.82 kmol/m3 HCl and H2SO4 solutions has been investigated as functions of stress and solution temperature by using the constant load method. It is found that the stress vs time-to-failure curves for both alloys are divided into three regions that are dominated by either stress, SCC, or corrosion. In the SCC-dominated region, the logarithm of time-to-failure is a linear function of the logarithm of the steady-state elongation rate (dimension in m/s), which is obtained from the corrosion elongation curve (elongation vs time), both under constant stress, regardless of material, anion species, and temperature, and under a fixed solution condition, regardless of stress and material. This result shows that the steady-state elongation rate becomes a relevant parameter for the prediction of time-to-failure. Furthermore, the steady-state elongation rate below which no fracture occurs within a laboratory time scale (<107 s) is estimated to be 10−10 m/s and less. It is also found that the ratio of crack-induction-time to time-to-failure holds constant (0.57 ± 0.02), independent of temperature, stress in the SCC region, anion species, and material. On the basis of the results obtained, the critical values of stress and temperature below which no SCC occurs are speculated.