Electrical properties and corrosion resistance of APS Al2O3-TiO2 coatings

Atmospheric plasma sprayed (APS) Al2O3 TiO2 coatings are used decades in many industrial applications. Commercially available powders contain 3, 13 and 40% TiO2 and differ significantly with respect to the homogeneity of distribution of aluminum and titanium and the phase composition. This strongly influences their processability, and, consequently the coating properties, which have not been systematically studied so for the full composition range. In order to complete the picture experimental spray powders with special compositions and structure were prepared. In total 13 commercial and four experimental spray powders containing 0, 3, 13, 40, 80, 100 wt.% TiO2 were used in this study to prepare coatings. As part of a larger project, in this contribution focus is made on the electrical properties (dielectric strength, electrical resistivity) and the corrosion resistance against 1N H2SO4 for 300 h and molten glass at 800°C for 4 h for the coatings of this sys. The results are discussed linking microstructure and phase composition with the electrical and corrosion properties.