Effect of Al content on in-situ formation of Al2O3 protective layer on Ni-Al coatings in high-temperature chloride molten salt

Abstract

The microstructure, strength, toughness, and resistance to chloride molten salt corrosion of Ni-Al coatings with varying Al content were investigated. Increasing the Al content from 9.9 to 61.1 at.% resulted in a decrease in adhesion strength and toughness, while an increase in corrosion rate. Contrary to previous reports, it is noteworthy that Ni-Al coatings with the lowest Al content exhibited superior resistance corrosion due to the formation of an oxidation layer which effectively blocked corrosion. This protective layer was primarily in-situ formed through the reaction between crystalline water present in the molten salt and an appropriate amount of Al. The balance between Al and O content is precisely regulated, resulting in the in-situ formation of Al2O3 protective.