Reduced Passivity and Enhanced Pitting Around Crack Tip Measured Using Scanning Electrochemical Cell Microscopy

Abstract

Stainless steels, widely used in industrial applications, are often subjected to combined corrosive and mechanical stress conditions, leading to corrosion fatigue. Herein, it is investigated how stress-induced deformation impacts the localized corrosion behavior of the CA6NM martensitic stainless steel using oil-immersed scanning electrochemical cell microscopy (SECCM). Compact tension specimens are cyclically loaded to induce plasticity around a growing crack, and electrochemical properties are mapped with high spatial resolution. The electrochemical activity is progressively changed near the crack, with open circuit potential and corrosion potential shifting toward more active values as the distance to the crack decreases. Pitting is also more frequent closer to the crack, gradually declining further away, indicating a spatial dependence in localized corrosion behavior. These findings help understanding how mechanical stress modifies passivity and pitting susceptibility, contributing to a better understanding of corrosion-fatigue mechanisms and materials design.