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The interaction of different metal oxides such as AL2O3, TiO2, ZrO2, SiO2, Nb2O5, Ta2O5, Cr2O3, MoO3, WO3, Fe2O3, Co3O4 and NiO with NaCl in the temperature range 800–1200 K in flowing oxygen has been studied. These oxides are present on the scales formed on Na2SO4 or NaCl during the initiation stage of hot corrosion attack and react with Na2SO4 or NaCl during the propagation stage by a fluxing reaction. Thermogravimetric, optical metallography, scanning electron microscopy, {EDAX} and X-ray diffraction techniques were used to identify and to determine the structure of various phases present in the solid state reaction products. The concentration of soluble metal and chloride species in the aqueous solutions of the reaction products of NaCl and metal oxides was determined using atomic absorption spectrophotometry and ion selective electrode analysis respectively. The solid state products usually contain a three-phase structure, i.e. Na2O.M2Ox, {MO} and Cl−. The concentration of various constituents varies according to the composition of interacting species, e.g. metal oxide and NaCl. The formation of Na2O.M2Ox depends upon the solid state solubility of metal oxides in the salt at high temperature.
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