Hot corrosion of Inconel 625 and NiCrMoAl alloys induced by KCl–55 %ZnCl2 molten salt films in air

This paper primarily investigates the corrosion behavior and mechanisms of Inconel 625 and NiCrMoAl alloys under KCl-55%ZnCl 2 salt films at 550 °C and 650 °C. The results indicate that the weight loss of the NiCrMoAl alloy was reduced by 70.36% and 71.53% at 550 °C and 650 °C for 50 h, respectively, compared to the Inconel 625 alloy. This is mainly because the α-Mo solid solution in the NiCrMoAl alloy exhibits good chemical stability, effectively inhibiting high-temperature chlorine corrosion. Cross-sectional morphology of the corrosion products on both alloys revealed that a dual-layer corrosion product formed on the Inconel 625 alloy surface, with an outer Ni-rich layer and an inner Cr-rich layer. Additionally, a selective dissolution zone of Cr formed at the corrosion interface, preventing the reformation of a protective Cr 2 O 3 layer. In contrast, the corrosion products on the NiCrMoAl alloy surface were primarily loose Al 2 O 3 . This is attributed to the high reactivity of Al, which can not only undergo chlorination with Cl 2 formed during corrosion but also directly react with ZnCl 2 via a displacement reaction to form AlCl 3 , thereby causing preferential dissolution of Al from the β-NiAl phase in the NiCrMoAl alloy.