Formation of Ti–Si composite oxide films on Mg–Al–Zn alloy by electrophoretic deposition and anodization

TiO2 or SiO2 nanoparticles dispersed in an acetone solvent containing iodine were deposited on Mg–Al–Zn alloy by electrophoretic deposition (EPD). Subsequently, the composite oxide films were formed on the substrate by anodization in KOH–Na2SiO3 aqueous solutions containing TiO2 or SiO2 nanoparticles. The films formed by EPD were improved binding with the substrate by anodization under high voltages with sparking, and then the anodic films consisted of Si–Mg or Ti–Si–Mg composite oxides. The film thicknesses of TiO2 and SiO2 on the alloy increased with anodization time. In polarization tests, the films anodized under high voltages with sparking in the alkaline solutions had high corrosion resistance. Thus, the composite oxide films formed in the present method were successful in providing corrosion resistance to Mg alloy.