A Comparative Analysis of Conventional Slurry Spray and Thermal Spray Coatings for Anti-Slagging and Corrosion Resistance for Boilers

Abstract Slag deposition and high-temperature corrosion are major ash-related issues in biomass-fired boilers. Protective coatings are used as countermeasures to these challenges. The coatings are produced by methods such as slurry spray and thermal spray. Nevertheless, studies on the comparative performance of these coatings on slag deposition and corrosion resistance are limited. Furthermore, there is currently no standard method to evaluate the anti-slagging capabilities of boiler coatings. Therefore, this study investigated and compared the slag and high-temperature corrosion resistance of a slurry spray coating and its thermally sprayed counterparts: atmospheric plasma spray and suspension plasma spray coatings. Anti-slagging evaluation of the coatings was conducted using an in-house “slag testing rig”, which was designed to investigate coating performance under simulated boiler conditions. A suspension plasma spray coating with a cauliflower-like surface exhibited the largest biomass fly ash reduction of ~ 12% by weight, which was contributed by the formation of air pockets at the interface between the biomass ash deposit and the coating. The slurry spray coating provided the highest corrosion resistance capability against molten salts with a linear corrosion rate constant of 3.40 × 10 -4 mg/cm 2 ·s ( p = 0.003).