Effects of U‐Bending on Pitting Corrosion of 304L Stainless Steel

The influence of cold U‐bending on pitting corrosion of 304L stainless steel in an acidic NaCl solution was investigated using surface analyses and electrochemical measurements. The pitting behaviour of the exterior and interior surfaces of U‐bended specimen exhibiting tensile and compressive residual stress respectively were both considered. The results show that microstructural modification by U‐bending promotes the pit nucleation. Considering the passive film properties after U‐bending, no significant change of both the thickness and Cr/Fe ratios of the passive films formed on the two deformed surfaces can be found. The accompanying residual stresses after U‐bending, especially the tensile residual stress, exhibits a remarkable acceleration of the metastable pit growth rate. Therefore, the pitting potential declines significantly for the exterior surface of U‐bended specimen. However, the compressive residual stress in the interior surface facilitates the repassivation of the metastable pit, can nullify the negative effect of microdefects for the pitting corrosion resistance, so that the pitting potential of the interior surface of U‐bended specimen doesn't decrease. This article is protected by copyright. All rights reserved.