The dissolution and passivation kinetics of stainless alloys containing molybdenum—II. Dissolution kinetics in artificial pits

Abstract

Artificial pit electrodes of FeCrNi and FeCrNiMo alloys have been polarized in a neutral 1M KCl solution at 22°C. The active dissolution kinetics in the nearly saturated pit environments have been determined; 1.6 at % Mo depresses the anodic dissolution rate in the active region by a factor of 5–10, depending on the potential. The consequent displacement of the corrosion potential in the pit is approximately the same as the change in pitting potential caused by the molybdenum addition. Experiments with 0.0065M sodium thiosulphate added to the bulk solution indicate that the alloy containing molybdenum is considerably less sensitive to the activating effect of adsorbed sulphur.