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

摘要

A sensing plate for the simultaneous pH and Cr 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 (Fe-18Cr-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 CI 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 Cr concentration were observed in the local repassivation area of the crevice corrosion.