Effect of SiO2 Sol Sealing on Corrosion Resistance of Anodic Films of AZ31 Mg Alloy

Silica sol was used to seal the pores of anodic oxide film of AZ31 magnesium alloy. The effect of the immersion time, the calcinating temperature and the immersion times on morphology and corrosion resistance of the film was discussed. Scanning electron microscope (SEM) was employed to characterize the surface morphology of the composite film, and potentiodynamic polarization curves were used to analyze the corrosion behaviors. The surface composition of the sealed anodic films was studied by energy dispersion spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). It has been found that the corrosion resistance of anodic film is improved by sealing by silica sol. When the dipping time is 1.5 min and the calcination temperature is 350 °C, the corrosion resistance of the film is the best. Times of dipping and calcination have a greater influence on the performance of the film. When the dipping-calcination is 7 times, the film has a good corrosion resistance. After sealing, silica sol is adsorbed on inner pores and outside pores of the anodic oxidation film.