High temperature corrosion of Hastelloy C22 in molten alkali salts: The effect of pre-oxidation treatment

Abstract The optimum protective oxide layer was expected to provide protection and reduce the corrosion damage of superheater material. The corrosion behaviour of raw and pre-oxidised Hastelloy C22 was investigated by exposing the selected samples to molten alkali salts (95.5 wt% KCl +4.5 wt% NaCl) at 700 °C for 100 h. The pre-oxidised Hastelloy C22 exhibited better corrosion resistance than raw Hastelloy C22 during exposure to molten alkali salt. The pre-oxidation treatment delayed the penetration of the corrosive reagent into the superalloy substrate. Schematic models of oxidation behaviour and corrosion mechanism in molten salts were presented in this work.