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An anticorrosion conversion coating on metal magnesium surface was prepared using immersion method in an aqueous solution containing mainly phytic acid. The coating after the preparation could be dry in the air without a rinse process using water in the final stage. Hence there is no discharge of waste water and waste gas in the whole process. Influence of several factors on the anticorrosion performance of coating was tested. And optimal parameters in the coating formation process were obtained from orthogonal test. The results indicated that the coating had better corrosion resistance, when the solution contained 3% phytic acid, and the immersion time is 7 minutes and the PH value was 3.5. The surface conversion coating was characterized by SEM and EDS. The conversion coating is better than the traditional chromate passive film by testing corrosion speed of coatings using hydrogen evolution method. The technology of the environment-friendly conversion coating containing phytic acid has the potential to be a new anti-corrosion technology for magnesium surface.

An Al coating and black passive film technique was developed in this research. Meanwhile, a fine and uniform Al coating with good binding force on steel surface was prepared. And a black passive film was used as a post-treated film of the electroplated Al coating. The result proves that the corrosion resistance of electroplated Al coating was over one time higher than that of zinc coating by black passivation. Besides, Al coating was less brittle with good ductility and, it could be used as a pretreatment layer before conducting laser heat treatment to significantly improve the efficiency of laser heat treatment.

A composite phosphate film was formed on magnesium aluminum (Mg-Al) alloy which was impregnated in phosphating solution containing phosphate, cerium salt, organic ammonium and corrosion inhibitor. The sample was examined by scanning electron microscope (SEM), X-ray diffraction (XRD), and Energy Dispersive Spectrometer (EDS) to analyze the organization and structure of the film. Additionally, the corrosion resistance of the film of composite phosphate was also investigated by salt spray test. As a result, it shows that the components of the film formed on Mg-Al alloy contain phosphates and elemental zinc. On the other hand, the composite phosphate film possessing photo-absorption property can be used for protective layer and laser pretreatment of Mg-Al alloy.