STRESS-CORROSION CRACKING OF TYPE-430 FERRITIC STAINLESS-STEEL IN CHLORIDE AND SULFATE-SOLUTIONS

The effects of stress, pH, and solution temperature on stress corrosion cracking (SCC) of type 430 (UNS S43000) ferritic stainless steel have been investigated in 0.82 kmol/m3 acidic chloride and sulfate solutions using a constant load method. The steady-state elongation rate obtained from corrosion elongation curve (elongation vs time curve) shows a linear function of time to failure with a slope of - 1.5 (as a function of stress) and with a slope of unity (as a function of pH and solution temperature under a constant stress condition). This implies that the steady-state elongation rate can be applied to type 430 as a parameter for prediction of time to failure as we# as that of austenitic stainless steels already reported. Furthermore, the steady-state elongation rate becomes a parameter for the criterion on evaluation of SCC susceptibility. By using a linear equation and the criterion for evaluation of SCC susceptibility, critical values of pH and solution temperature on SCC under the present experimental conditions are estimated. It is also found that type 430 has less susceptibility to SCC in the chloride solution than in the sulfate solution. The results obtained are compared with those for austenitic stainless steels.