Fabrication and Corrosion Resistance of Plasma-Sprayed Glass-Powder-Doped Al2O3-13 wt.%TiO2 Coatings

Silicate-based glass powder was prepared and doped into commercially used Al2O3-13 wt.%TiO2 powder (AT13) for plasma spraying. The morphology and phase structure of the glass-doped AT13 coating (G-AT13) were characterized by scanning electron microscopy/energy-dispersive spectroscopy and x-ray diffraction analysis. The results revealed that the glass particles were able to fully spread to adapt to the roughness of the ceramic sheet layer and fill the pores between the ceramic particles, thereby reducing defects such as pores and microcracks inside the coating layer. Compared with the AT13 coating, the G-AT13 coating was more compact with lower porosity of 4.2% and higher microhardness of 1938 HV. After 2400 h of immersion corrosion in 3.5 wt.% NaCl solution, the AT13 coatings displayed severe corrosion with cracks and rust on the surface, whereas the G-AT13 coating only exhibited a small amount of rust on the surface. Electrochemical measurements (Tafel polarization and electrochemical impedance spectroscopy) also indicated that the G-AT13 coating possessed higher corrosion resistance than the pure AT13 coating. Doping of glass into the ceramic coatings therefore improved the long-term corrosion resistance of the coatings.