Insight into the corrosion resistance regulation of dislocation density in cold-rolled 304 stainless steel thin strips

Grain refinement through cold rolling enhances both the mechanical properties and corrosion performance of SUS304 thin tape. With increasing rolling reduction, the material's yield and tensile strength gradually increase, while the improved surface roughness suggests a reduced surface area for corrosion nucleation. Notably, the sample with a 15% reduction rate (Rate-3) develops a microstructure characterized by a high dislocation density and a larger proportion of low-angle grain boundaries (LAGBs). These LAGBs contribute to higher yield strength due to their low energy and greater structural stability. Crucially, they also improve resistance to intergranular corrosion by disrupting the interconnected network of random high-angle grain boundaries (HAGBs), thereby impeding the penetration of corrosive agents. Electrochemical tests in 3.5% NaCl solution confirmed the enhanced corrosion resistance, showing a rise in the self-corrosion potential and a decrease in the corrosion current density with greater rolling reduction. Rate-3 exhibited optimal values of -0.12 V (vs. SCE) and 4.812 μA cm⁻², respectively. XPS analysis indicated that this improved performance originates from the formation of a dense, oxide-enriched dual-layer passive film. The refined grains and high dislocation density provide increased nucleation sites for oxide formation, enhance adhesion work, and promote more uniform capillary forces, collectively leading to a more uniform and compact passive film. This was further supported by Mott-Schottky analysis, which revealed a significant reduction in defect density within the passive film after severe rolling deformation. These findings demonstrate that microstructural engineering via cold rolling is a viable strategy for tailoring the corrosion resistance of stainless steel, offering theoretical guidance for its application in complex environments.