Evaluation of the corrosion behaviour of plasma-sprayed Ni3Al coatings on steel in oxidation and molten salt environments at 900 °C

Ni3Al coatings were obtained on boiler tube steels through a plasma spray process. Ni–Cr–Al–-Y was used as a bond coat before applying Ni3Al coatings. Characterisation and hot corrosion behaviour of coatings after exposure to air and molten salt at 900 °C were studied under cyclic conditions. The Ni3Al coating was very effective in decreasing the corrosion rate in air and molten salt at 900 °C in the case of ASTM-SA210 grade A1 and ASTM-SA213-T-11 types of steel. whereas the coating was least effective for ASTM-SA213-T-22 steel. Uncoated ASTM-SA213-T-22 steel showed very poor resistance to hot corrosion in molten salt environment, with spalling of the oxide scale.