Original paper(Vol.48 No.11 pp.1228)

Stress corrosion cracking of solution annealed austenitic stainless steel type 304 in sulfuric acid-sodium chloride solution - effects of NaCl concentration and chromate

Nishimura Rokuro; Yamakawa Koji

Abstract:Stress corrosion cracking (SCC) of austenitic stainless steel type 304 has been investigated as functions of chromate concentration and test temperature in 0.82 kmol/m3 H2SO4-NaCl solution under a constant applied load by using a constant load method. The linear relationship between the logarithms of time to failure and steady state elongation rate was obtained under a constant applied stress of 388 MPa (or 392 MPa) irrespective of NaCl concentration, chromate concentration and test temperatures as follows: log lss = -log tf + C. Under the present experimental conditions, the steady state elongation rate was found to be a useful parameter both for predicting time to failure and for the assessment of SCC susceptibility. The critical chromate concentration (CcriNa2CrO4) and critical test temperature (Tcri) were estimated under a constant nominal stress of 388 MPa and were obtained below, respectively;
log CcriNa2CrO4 = 0.70 logCNaCl - 0.73
103/T cri = -0.64logCNa2CrO4 + 2.11
The results obtained were discussed in terms of ion selectivity of film formed, corrosion current density at crack tips and the length of crack propagation.

Key Words:chromate, SCC, steady state elongation rate, prediction, time to failure, critical value, sulfuric acid, sodium chloride