Abstract
The present work investigates the effect of hot corrosion on ASTM-SA213-T-22 Steel with different coatings of Al2O3-TiO2 at 900℃ in molten salt environment (40wt %Na2SO4+60wt%V2O5). The experimentation consisted of 50 cycles of heating coated and uncoated specimens for 1 hour at 900℃ in muffle furnace and cooling for 20 minutes at ambient temperature. The corroded specimens were analyzed using visual examination, weight change measurement, X-ray diffraction technique and Scanning electron microscopy/Energy-disperse X-ray analysis. The results showed that the uncoated substrate had been more affected with corrosion and gained more mass due to formation of iron oxide (Fe2O3) as compared to coated substrate because of better adhesion of Al2O3 coating with base metal SA213-T22 due to presence of TiO2. The presence of TiO2 increased the strength and durability of Al2O3 coating to withstand with high temperatures.
Highlights
The corrosion occurs at elevated temperatures due to exposure of steels and alloys in atmosphere, which causes formation of oxide layer, when the environmental oxygen reacts with ferrous metal, and is called hot corrosion [1,2,3,4]
The failure occurs in boiler tubes is due to the corrosion of base metal at elevated temperature in the molten salt environment which results in damage to the physical and chemical properties of the substrate [5,6,7]
The experiment was conducted in a molten salt environment (40wt% Na2SO4-60wt% V2O5) kept in silicon tube muffle furnace at 900°C
Summary
The corrosion occurs at elevated temperatures due to exposure of steels and alloys in atmosphere, which causes formation of oxide layer, when the environmental oxygen reacts with ferrous metal, and is called hot corrosion [1,2,3,4]. The failure occurs in boiler tubes is due to the corrosion of base metal at elevated temperature in the molten salt environment which results in damage to the physical and chemical properties of the substrate [5,6,7]. This can be prevented by applying thin layer of coating on the surface of base metal by the various coating processes like plasma spray coating, high velocity oxy fuel (HVOF) and powder coating etc. The corrosion rate is highly dependent on the presence of corrosive elements, such as Na2SO4 and V2O5 in atmosphere with elevated temperature
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