Electrophoretic deposition and thermal treatment of boehmite coatings on titanium

Abstract

An aqueous boehmite sol was prepared by the peptization of Al(OH)3. The electrophoretic deposition of boehmite coatings on titanium from the aqueous sol was performed at a constant voltage (from 1.0 to 10 V) and for a constant deposition time (from 10 to 30 min). Increasing the applied voltage and deposition time increased the mass of the boehmite coating. It was shown that boehmite coatings of maximum thickness, low porosity and good adhesion can be formed at lower deposition voltages and longer deposition times. The boehmite powder, obtained by drying the prepared aqueous sol, and the boehmite coatings were thermally treated at 1000°C and 1300°C with a holding period of 1 h at the maximum temperature. X-Ray diffraction analysis of the thermally treated samples confirmed the existence of γ-Al2O3 and α-Al2O3 phases, respectively, while scanning electron microscopy revealed the graininess of the structure of the α-Al2O3 coatings treated at 1300°C, indicating a significantly lower sintering temperature of the boehmite coating obtained by electrophoretic deposition.