Emergence of micro-galvanic corrosion in plastically deformed austenitic stainless steels

Localized plastic deformation has been observed to render nuclear reactor components more susceptible to stress corrosion cracking (SCC). However, it is not fully clear how localized strain impacts corrosion (oxidation) behavior. Herein, the surface reactivity and corrosion behavior of 304 L stainless steel specimens, deformed to different strain levels, was analyzed using advanced multimodal and multiscale methods. For the first time, we observed that localized deformation regions, e.g., deformation bands and ??-martensite featured smaller Volta potentials than the parent austenite matrix. This resulted in the establishment of localized corrosion potential gradients and the emergence of accelerated microscale galvanic corrosion. Particularly, regions that featured higher dislocation concentrations were more reactive on account of the reduction in the activation energy of corrosion due to the stored energy. The superposition of surface reactivity and strain distributions reveals that, SCC cracking is expected to initiate in regions of strain localization wherein micro-galvanic corrosion is favored. ? 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Localized plastic deformation has been found to make nuclear reactor components more susceptible to stress corrosion cracking (SCC). By analyzing the surface reactivity and corrosion behavior of deformed stainless steel specimens, research has shown that regions with higher dislocation concentrations exhibit increased reactivity due to a reduction in corrosion activation energy. The combination of surface reactivity and strain distributions suggests that SCC cracking is likely to occur in areas with localized strain where micro-galvanic corrosion is favored.