Corrosion mechanisms of 316L stainless steel in supercritical water: The significant effect of work hardening induced by surface finishes

•Oxidation behavior of 316L SS in SCW strongly depends on subsurface work-hardening.•Ionic image highlights reaction interfaces of double-layered oxides.•Reaching a hardening threshold leads to a considerable thinning of the oxide scale.•Diffusion of hydrogen through the oxide scale leads to H uptake by the alloy.