Microstructure evolution and corrosion behaviors of cold-rolled 304 stainless sheets of steel in 3.5% NaCl solution

Abstract

Austenitic stainless steel (ASS) is widely used in engineering applications due to its good corrosion resistance and mechanical properties. Several studies have indicated that the deformation-induced transformation of martensite in ASS significantly affects its corrosion resistance. However, corrosion resistance behavior in chloride-rich environments is more complex, and different cold-working methods have distinct impacts on localized corrosion. This study investigated the structural and corrosion resistance changes induced by cold rolling in AISI 304 samples. The used samples were initially subjected to a cold-rolling process with a thickness reduction of up to 50%. The results demonstrate an increase in the deformation-induced martensitic transformation and micro-hardness as the level of cold deformation increases. However, higher levels of deformation lead to the fragmentation of the formed a’‑martensite lath structure into smaller laths, ultimately resulting in a predominantly refined and diffuse dislocation-cell-type structure. Potentiodynamic tests were conducted to analyze conventional electrochemical parameters, revealing a reduction in corrosion resistance with increasing cold deformation. This suggests that the formation, amount, and microstructure of a’‑martensite, under imposed strain conditions, induce changes in the studied electrochemical parameters. Additionally, the more deformed samples exhibited a higher current density during passive layer formation, and exhibited more intense metastable pits, suggesting decreased corrosion resistance with higher degrees of deformation.