Repassivation kinetics in stress corrosion cracking—I. Type AISI 304 stainless steel in chloride solutions

Abstract

The repassivation kinetics of AISI 304 austenitic stainless steel was studied in 0.5 M Na 2SO 4 solution, 1 M HCl solution and 1 M NaCl solution, at room temperature and at various electrode potentials. Under the experimental conditions used in the present work, stress corrosion cracking (SCC) of the steel was known to occur only in the HCl solutions. The repassivation kinetic results were described by relations of the type i = A· t b . In Na 2SO 4 solutions b = −1 was found. In NaCl solutions and in HCl solutions b = −1 was found only in the first 100 ms after straining. In the next 10 s a value of b = −0.5 was recorded, and for longer exposures values of b = 0.5 and b = 1 were observed. There is strong evidence that a dissolution-precipitation film formation mechanism is involved in the region where b = −0.5. By comparing the results in HCl solutions with those in NaCl solutions, slow repassivation, of the type b = −0.5, is concluded to be a necessary but not sufficient electrochemical condition for SCC susceptibility.