On the effect of cold-rolling on the corrosion of SS316L alloy in a molten carbonate salt

Abstract

Interactions between stainless steel 316L and eutectic Li2CO3 + K2CO3 + Na2CO3 at 450 °C were investigated for thermal energy storage. Scanning Electron Microscopy (SEM), Electron Back-Scatter Diffraction (EBSD), Scanning Kelvin Probe Force Microscopy (SKPFM), X-ray Photoelectron Spectroscopy (XPS), neutron diffraction pattern, material loss, micro-hardness, polarization and impedance measurements were used to compare the alloy's response in unrolled (0%) condition versus 20% and 30% cold-rolled conditions. Cold-rolling increased the number of grains, grain boundaries and density of dislocations. Initially, faster corrosion accompanied by more areas of localized attack was confirmed by Volta potential measurements. However, recovery and the formation of a surface film were found to decelerate corrosion for longer times. Cold-rolling-induced dislocations were found to facilitate carbon diffusion and subsequently carburize the material leading to increased corrosion resistance. Consequently, the overall long-time corrosion rate was not noticeably affected by cold-rolling.