<p>This study investigates the effect of polishing as a post-treatment for AISI 304 stainless steel (304 SS) subjected to surface mechanical attrition treatment (SMAT) using 8&#xa0;mm ∅ balls for 60 min. In addition, the passivation and transpassivation characteristics of untreated, SMAT-treated, and SMAT-treated + polished 304 SS in 0.5 M H₂SO₄ is evaluated. SMAT has led to the generation of a gradient microstructure from the top surface to the bulk via formation of a nanocrystalline structure at the surface; sub-micron sized and deformed grains at the intermediate region and unaffected grains at the bulk, as evidenced by the electron backscattered diffraction (EBSD) results. SMAT induced transformation of austenite (γ) to strain-induced martensite phase (α’) at the top surface. Post-polishing of 304 SS subjected to SMAT exhibited a higher corrosion resistance when compared to its as-treated counterpart. Post-polishing after SMAT promoted the formation of an intact passive film and enhanced the transpassive behaviour. X-ray photoelectron spectroscopy (XPS) analysis point out the formation of higher amount of Cr₂O₃ on post-polished 304 SS subjected to SMAT when compared to its as-treated counterpart. Surface microcracks and overworking exerts a major influence on the corrosion resistance of treated 304 SS besides the strain-induced phase transformation. The findings of the study reveal that post-polishing is a viable option to improve the passivation behaviour of treated 304 SS without compromising the desirable attributes imparted by SMAT.</p> Graphical Abstract <p></p>