Effect of TiO2 on the Repassivation Kinetics of Alloy 600 in Caustic Solutions

Abstract

Effects of titanium dioxide (TiO2) inhibitor on repassivation kinetics and defect density of the passive film formed on Alloy 600 (UNS N06600) were examined. Addition of 0.05 g/L TiO2 powder increased the repassivation rate of Alloy 600. Passive film initially nucleated and grew according to the place exchange model in which log i(t) is linearly proportional to q(t), and later it grew according to high-field ion conduction model in which log i(t) is linearly proportional to the 1/q(t). Ti enrichment in the film decreased the defect density of the film and increased its protectiveness.