Anodisation of AZ91D magnesium alloy in molybdate solution for corrosion protection

We report the formation of a protective film on magnesium alloy AZ91D by means of anodisation under potentiostatic conditions in a molybdate solution. Results of the characterisation of the films by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are presented. The anodic film is mainly composed by magnesium oxides or hydroxides and molybdenum oxides. The corrosion protection performance of the coating was investigated in Ringer solution by monitoring the open circuit potential, polarisation techniques and electrochemical impedance spectroscopy (EIS). The coated electrodes exhibit significant corrosion protection properties due to the presence of molybdenum species in the film.