Hot Corrosion Behaviour of Sol-Gel Alumina Coated IN625 Alloy in Alkali Metal Chlorides and Sulphates Salt Deposit Systems

Abstract

Sol-gel derived alumina coating was applied on Inconel 625 alloy using dip coating technique and their hot corrosion studies were carried out in LiCl-NaCl and Na₂SO₄-K₂SO₄ salt deposits system at 650 °C and 850 °C respectively.  Oxidation kinetics measurement indicated the occurrence of an order of magnitude lower oxidation rate and around 15–20 % higher activation energy for the coated substrate as compared to uncoated one. EDS analysis of the oxidized substrate suggested that some of the Al of the coating get dissolve due to the fluxing of the salt melt. On the basis of microstructural examination and elemental X-ray mapping through scale/coating interfaces of the oxidized substrate, oxidation mechanism has been discussed.