Effects of Thermal Spray Coating Composition and Microstructure on Coating Response and Substrate Protection at High Temperatures

Three thermal spray coatings were subjected to high-temperature corrosion experiments to characterize the operative corrosion mechanism(s) and to examine the effects of coating composition and microstructure. Samples were placed in air and sulfur dioxide (SO₂) at 600°C for exposure times up to 1,000 h. The ability of a thermal spray coating to protect its substrate effectively was found to depend upon its tendency to form protective oxides and upon the cross-sectional distance from the coating surface to the substrate via fast diffusion paths such as splat boundaries and voids.