Anodization of AZ91 magnesium alloy in alkaline solution containing silicate and corrosion properties of anodized films

The anodization of AZ91 magnesium alloy in an alkaline electrolyte of 100 g/L NaOH+20 g/L Na2B4O7·10H2O+50 g/L C6H5Na3O7·2H2O+60 g/L Na2SiO3·9H2O was studied. The corrosion resistance of the anodized films was studied by electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization techniques. The microstructure of the films was examined with scanning electronic microscope(SEM) and X-ray diffractometer(XRD). The results show that, under the experimental conditions, the optimum anodizing time and the optimum anodizing current density are 40 min and 20 mA/cm2 respectively for obtaining the anodic film with high corrosion resistance. The XRD pattern shows that the components of the anodized film consist of MgO and Mg2(SiO4).