Dip coating of alumina films by the sol-gel method

Thin alumina films were prepared on stainless steel and glass surfaces by dip coating from an aluminum alkoxide solution. Multiple coatings from a low-viscosity solution were necessary for high quality and sufficient thickness of the films. To determine the bonding mechanism and strength, wavelength dispersive x-ray was used. Aluminum was found to diffuse into the substrate in both cases. The possible bonding mechanism is a combination of diffusion and the formation of chemical compound between the alumina and the substrates. The surface properties of stainless steel, such as microhardness, electric resistance, and corrosion resistance, were substantially improved when coated with alumina.