Impact of hydroxide ion–chloride ion concentration ratio on crack electrochemistry

A model of the electrochemistry in a stress corrosion crack in martensitic stainless steel in low-chloride containing solution has been applied to predict the impact of the hydroxide ion–chloride ion ratio in the bulk solution on the local electrode potential and solution chemistry. Computations were undertaken for bulk chloride ion concentrations between 0.1 and 1000 ppm (by mass) and bulk pH values between 6.0 and 11.5. For near-neutral pH, a significant deviation of crack-tip electrochemistry from the bulk electrochemistry is predicted. However, above pH 9.5, a hydroxide-dominated regime is encountered with uniformity of potential, pH and chloride concentration.