Hot Corrosion Performance Analysis of Microwave Heat-Treated Al₂O₃-Based Coatings Deposited on SA 210 Grade-I Boiler Steels

The selection of the boiler steel SA-210 for this particular application is attributed to its utilization in boilers. The primary factors contributing to surface deterioration in boilers are hot corrosion and oxidation processes. The three coatings used to reduce surface damage from heat corrosion and oxidation were Al₂O₃ (AL), Al₂O₃ + 13% TiO₂ (AL13TI), and Al₂O₃ + 40% TiO₂ (AL40TI). The hot-corrosion and high-temperature oxidation properties of SAE 210 steel, both coated and bare. Coated and uncoated specimens were oxidized cyclically for 50 cycles in atmospheric air and melted salt containing a blend of Na₂SO₄ and 4–60% V₂O₅ at 900 °C. We analyzed the corrosion products using SEM/EDAX, XRD, and thermogravimetric methods. Properties such as coating thickness, constituent distribution, and surface morphology were also examined in the as-coated boiler steel. The molten salt environment with Na₂SO₄-60% V₂O₅ at 900 °C for 50 cycles has shown that the coated boiler steel with the AL40TI post-treatment can resist corrosion at higher temperatures for a longer duration than the untreated SA 210 Grade -I steel. The minimum hot-corrosion in the PT-AL40TI treated samples was because after heat treatment, the refinement of the microstructure restricts the salt attacks on the surface thereby decreasing the degradation.