Research on Anodizing of Magnesium Alloy in Environment-Friendly Electrolyte with Nano-Al2O3

Anodizing is an effective way to improve the corrosion resistance of magnesium alloys. In this paper, an environmentally friendly electrolyte which is free of chromate, fluoride or any other poisonous ingredients was developed for the anodizing of magnesium alloy AZ91D. Additionally, nano-Al₂O₃ was added to this electrolyte. The anodic film can form rapidly in this electrolyte in only 1 minute. The corrosion resistance of the anodic films formed both in the electrolyte with and without nano-Al₂O₃ was investigated by immersion test and potentiodynamic polarization technique. The results showed that the anodic films mentioned above can improve the corrosion resistance property of the alloy surface significantly. And compared with the sample without nano additive, the addition of nano-Al₂O₃ to the electrolyte can not only enhance the corrosion resistance of the film but weaken the anodizing reaction dramatically without prolonging the formation time of the film.