Electrochemical evaluation for sensitization of austenitic stainless steels using neutral solution

Austenitic stainless steels (JIS SUS 304) were sensitized at 923K for various times and the extent of sensitization was evaluated in 0.6 kmol/m(3)NaCl solution, using two electrochemical methods: cyclic voltammetry and potential step chronoamperometry. Cyclic voltammograms indicated that sensitized specimens had two types of pitting corrosion, one for chromium depleted zone and the other for grains. The pitting potentials for both types of corrosion measured by cyclic voltammetry had no significant relation to the extent of sensitization. Potential step chronoamperometry was then applied to the evaluation. The potential step chronoamperometry to the pitting potential for grains gave no significant correlation with the sensitization, and the plotted data were scattered randomly. On the other hand, the time integral of current density calculated from potential step chronoamperometry at the pitting potential for chromium depleted zone increased with the extent of sensitization. The latter case can be utilized for the evaluation of sensitization.