Improvement in the corrosion resistance of TiB2/A356 composite by molten-salt electrodeposition and anodization

This study reported a novel treatment to improve the corrosion resistance of TiB2/A356 composites. The method was employed in combination of the molten-salt electrodeposition and subsequent electrochemical anodization technique. By means of molten-salt electrodeposition, the Al coatings were deposited on the surface of TiB2/A356 composites. It was found that the morphology of the Al coatings is closely related to the current density. Thus, under the suitable condition, a dense and uniform Al coating can be obtained, with the crystal size in the range of 0.5–2 μm and the coating thickness of ~ 9 μm. This continuous Al layer can eliminate the adverse corrosion contribution of TiB2 particles in Al matrix. The following step of anodization was designed to convert the Al film to an anodized Al oxide film for further corrosion protection. The electrochemical corrosion behavior was evaluated by potentiodynamic polarization curves and electrochemical impedance spectroscopy. These results showed the corrosion resistance was greatly enhanced in TiB2/A356 composites with an anodized Al-coating than that of the anodized composites. It is evident that the new treatment of metal electrodeposition in molten salts and following anodization is an effective method of anti-corrosion in composites.