Comparative study of hot corrosion behavior of thermal sprayed alumina and titanium oxide reinforced alumina coatings on boiler steel

Abstract

The current work evaluates the effect of hot corrosion on ASTM-SA213-T-22 Steel with a coating of 100Al2O3 and 20TiO2-Al2O3 at 900 °C in the molten salt environment of (Na2SO4-60% V2O5). The coatings were sprayed by plasma spray technique. The bare and coated samples were placed inside the muffle furnace at 900 °C for 50 cycles. Each cycle consisted of heating for 1 h and 20 min of cooling at ambient temperature. The kinetics of hot corrosion was analyzed by measuring mass gain after each cycle. The results were achieved by using visual examination, mass change measurement, XRD and SEM/EDS analysis. The result revealed that bare steel was more affected with corrosion and gained more mass due to the development of iron oxide (Fe2O3) than the coated sample. Fe2O3 and Cr2O3 were found as major phase in oxide scale of T-22 uncoated steel specimen. The 100Al2O3 and 20TiO2-Al2O3 coated specimen indicated the reduction in mass gain by 25.41% and 67.02% respectively as compared to uncoated specimen. Al2O3 coating with the combination of TiO2 showed better adhesion properties. The presence of TiO2 enhanced the durability and strength of Al2O3 coating to withstand high temperatures.