Densification of SiO₂-Al₂O₃-TiO₂ based ceramic film coated on steel for high thermal stabilty and mechanical properties

The densification of a ceramic coating based on SiO₂-Al₂O₃-TiO₂ by using wet processing was investigated by adding excess alkali silicates. Ceramic composite films (80-100 μm thick) added alkali silicates were deposited on a steel plate by slurry coating with a doctor blade, followed by drying and calcination. The corrosion test in 1 mol/l HCl solution revealed that the number of through-holes in the coating decreased drastically with increasing the amount of alkali silicates (26, 30, 33, 40 wt.%) and the calcination temperature up to 800 °C. The coatings involving alkali silicates of 33 and 40 wt.% were stable to heating up to 800 °C for thermal shock tested in air. The adhesive strength was also found to increase by three times with increasing amounts of alkali silicates.