Visualizing the Crevice Corrosion Behavior of Nitrogen-Containing Stainless Steel: Changes in pH and Cl^－ Distributions with Initiation, Growth, and Local Repassivation

Abstract

A sensing plate for the simultaneous pH and Cl^－ concentration measurements was fabricated and used as a crevice former to visualize the pH and Cl^－ distributions inside the crevice of nitrogen-containing stainless steel （Fe18Cr-10Ni-5.4Mn-0.25N）. The initial morphology of the crevice corrosion of the nitrogen-containing stainless steel was a micro-pit. The initiation of the micro-pit led to a large decrease in pH and an increase in the Cl^－ concentration. The low pH and high Cl^－ concentration region expanded with crevice corrosion propagation. The initiation mechanism of the crevice corrosion of the nitrogen-containing stainless steel was quite similar to that of the nitrogen-free stainless steel （Fe-18Cr-10Ni-5.4Mn） reported in previous studies. An increase in pH and a decrease in the Cl^－ concentration were observed in the local repassivation area of the crevice corrosion.