Corrosion Resistance of Plasma-Sprayed Ceramic Coatings Doped with Glass in Different Proportions

To improve the corrosion resistance of Al2O3-13 wt.% TiO2 (AT13) coatings prepared by plasma spraying, CaO-MgO-Al2O3-SiO2 silicate glass powder was mixed with AT13 in different proportions (Glass/AT13 = 0/10, 1/10, 2/10 and 3/10, by mass). The morphology and structure of the coatings were characterized by field emission scanning electron microscopy/energy spectrometry, x-ray diffraction and confocal laser scanning microscopy. Their corrosion resistance was evaluated by immersion corrosion and electrochemical corrosion tests. The results show that the glass-doped composite coatings have lower porosity, higher microhardness and lower roughness than the pure AT13 coating. Therefore, the glass-doped coatings exhibited better corrosion resistance than the sealed AT13 coating. In addition, the composite coating with the doping ratio of 2:10 maintained the best overall corrosion resistance with low corrosion zones, low corrosion current values, high pitting potential and high polarization resistance. Therefore, the proper addition of glass frit, with its excellent characteristics of low viscosity and high fluidity at high temperatures during plasma spraying, can fully compensate for the high porosity of ceramic coatings. Proper doping with glass has excellent potential application to improve the corrosion resistance and service performance of plasma-sprayed ceramic coatings.