Electrochemical investigations on crevice corrosion of a martensitic stainless steel in a thin-layer cell

• A thin-layer cell was developed to reproduce the conditions met during crevice corrosion.
• Impedance measurements were performed in confined media.
• Critical conditions (pH and Cl− concentration) were determined for which the stainless steel cannot be passivated.

This paper focuses on crevice corrosion resistance of a martensitic stainless steel. First, electrochemical measurements were performed in deaerated bulk electrolytes for different chloride concentrations and different values of the pH to determine the critical parameters leading to dissolution or breakdown of the passive film. Then, a thin-layer cell was designed to confine the electrolyte between two parallel stainless steel planes. Impedance measurements obtained for different immersion times and electrolyte thicknesses clearly showed the influence of these two parameters on the crevice corrosion rate. A significant decrease of the corrosion resistance when the medium is increasingly confined was observed. The data obtained in the bulk electrolytes were used to determine the critical conditions in the thin-layer cell which impede the repassivation of the stainless steel (pH and [Cl−]).