Effect of Shot Peening on the Corrosion Behavior of 304 Austenitic Stainless Steel in Molten Solar Salt

Abstract

The effect of shot peening on the corrosion behavior of 304 austenitic stainless steel in molten Solar Salt (60 wt% NaNO 3  + 40 wt% KNO 3 ) at 550°C was studied. Shot peening markedly improves the corrosion resistance of 304 austenitic stainless steel. Electrochemical tests show a 35.2% reduction in corrosion rate, with current density decreasing from 0.281 to 0.182 mA cm −2 . After 2000 h of immersion, shot‐peened samples form a thin, compact, and adherent oxide scale with negligible spallation, unlike the porous, cracked scale on untreated steel. The surface deformation layer (~50 μm) introduced by shot peening—characterized by grain refinement, high dislocation density, and dispersed martensite—enhances Cr diffusion to the oxidation front. This promotes Cr enrichment in the inner oxide layer and subsurface Ni accumulation, thereby suppressing Fe oxidation and improving scale protectiveness for Concentrated solar power (CSP) applications.