Corrosion behavior of 316 stainless steel alloy in high temperature heat storage medium containing oxygen-chloride salt

Understanding the co-adsorption of O2- and Cl- is very important for studying the entire adsorption mechanism of 316 SS corrosion in ternary chlorine salts. The effect of O2 on the corrosion behavior of 316 stainless steel (SS) in ternary chloride salts is quantitatively studied through experiments combined with density functional theory (DFT) calculation and experiments. The experimental results such as Scanning Electron Microscopy (SEM) coupled with X-ray Photoelectron Spectroscopy (XPS) show that Cl- and O2- act on the alloy surface to accelerate the corrosion of 316 SS. DFT calculations show that O2- and Cl- caused more significant surface structure changes and electron losses of alloy surface than single O2- or Cl-. Moreover, the charge transfer of different alloying elements increases in the order of Ni < Fe < Cr. In addition, it is found that the passivation of 316 SS alloy is mainly attributed to the strong oxygen adsorption. The formation of alloy oxides sharply increases the work function on the 316 SS surface, thereby slowing down the corrosion rate of the 316 SS alloy. These research results are helpful in understanding the corrosion mechanism of 316 SS alloy in ternary chloride salts containing impurities under air conditions.