Repassivation kinetics and its role in SCC prediction- A review

This paper reviews the relationship between repassivation kinetics and stress corrosion cracking (SCC) susceptibility of materials in terms of cBV model developed using rapid scratch electrode technique (RSET). In this technique repassivation kinetics of the alloys was analyzed in terms of the current density flowing from the scratch, i(t), as a function of the charge density that has flowed from the scratch, q(t). Repassivation on the scratched surface of the alloys occurred in two kinetically different processes; passive film initially nucleated and grew according to the place exchange model in which log i(t) is linearly proportional to q(t), and then grew according to the high-field ion conduction model in which log i(t) is linearly proportional to 1/q(t). The slope determined from the log i(t) versus 1/q(t) plot (called cBV) was found to be a parameter representing the repassivation rate, stress corrosion cracking (SCC) susceptibility and protectiveness of the passive film.