High-Temperature Corrosion and Thermal Spray Protection of Heat-Transfer Surfaces in Municipal Solid Waste-to-Energy Boilers

Municipal solid waste-to-energy (MSW-WTE) boilers are increasingly operated at higher steam temperatures and pressures to improve efficiency. Under these conditions, heat-transfer surfaces are exposed to high-temperature oxidation, chlorine-induced corrosion, molten-salt corrosion and thermomechanically coupled damage, which compromise long-term operational safety. Thermal spraying offers flexibility in tailoring coating composition and microstructure and is therefore widely used to improve the service reliability of these surfaces. This review examines the corrosive environments, principal damage mechanisms and development of thermal spray protection systems for MSW-WTE boiler heat-transfer surfaces. It first considers how variations in temperature, flue-gas composition and deposit evolution among boiler regions influence corrosion behavior, with particular emphasis on chlorine-induced active oxidation, sulfate/chloride-assisted hot corrosion and molten-salt corrosion. It then relates spraying processes and coating microstructures to the corrosion-protection mechanisms, advantages and limitations of MCrAlY, NiCr/NiCrMo and carbide-reinforced coatings under different service conditions. Finally, future developments in multifunctional coatings, structural optimization and condition-based maintenance are discussed. By linking corrosive environments, damage mechanisms, coating structures and service reliability, this review provides a framework for the design and engineering application of protective coatings for MSW-WTE boiler heat-transfer surfaces.