The preparation and characteristics of a rare earth/nano-TiO2 composite coating on aluminum alloy by brush plating

Nano-TiO2 modified rare earth composite coatings are prepared on 2024 aluminum alloy by brush plating. The composite coating is composed of mainly Ce(OH)3, Ce(OH)4, CeO2 and TiO2, with less cracks and lower porosity. The addition of nano-TiO2 enhances the adhesive strength of the rare earth coating to Al substrate, results in refined coating grains and increases the micro-hardness of the coating. The nano-TiO2 modification obviously improves the corrosion resistance of the rare earth coating. For the composite coating containing 2% TiO2, both the corrosion current density and the impedance are reduced by more than one order of magnitude in contrast to the values for the pure rare earth coating. The higher barrier ability and increased Ce3+ content in the Ce oxides may explain the increase of the corrosion resistance.

► Nano-TiO2 modified Ce coating is prepared on 2024 aluminum alloy by brush plating.
► The composite coating shows finer grains, less cracks and lower porosity.
► TiO2 addition increases the adhesive strength and micro-hardness of the coating.
► Corrosion resistance of the Ce coating is greatly improved by nano-TiO2 modification.
► Increased barrier ability and Ce3+ content in coating may explain the effects of TiO2.