This study investigates the influence of pre-oxidation treatment on the corrosion of SS316L in molten solar salt with added chloride ions. The results show that bare SS316L is subjected to severe corrosion in a molten solar salt containing a large amount of chloride ions, with a loose oxide layer forming on the surface and exhibiting pronounced delamination. However, after being pre-oxidised at 800 °C for 5 h, a continuous and dense oxide layer on the surface of SS316L was formed. The pre-formed Fe3O4 and Cr2O3 oxide layer enables the oxide/matrix interface to maintain low oxygen and chlorine pressure, thereby slowing down the oxidation–chlorination reaction rate. Finally, corrosion products with a three-layered structure consisting of Fe2O3, Fe3O4, FeCr2O4 and NiFe2O4 are formed, which maintains the integrity structure during the whole immersion and improves the corrosion resistance of SS316L. Roles of the pre-oxidation mechanism give new insights into alloy protection in molten nitrates with chloride ions. It offers a novel approach to enhancing the corrosion resistance of next-generation concentrated solar power equipment.
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