| Magnesium alloys were recognized as the green engineering materials in 21st century because of their low density, high strength/weight ratio, relatively high thermal and electrical conductivity and reclamation property. The application of them in automobile,aerospace components,communication parts,3C equipments,mechanical equipments and so on, has been increasing in the past decade. However, magnesium has highly activity and its alloys usually have poor corrosion resistance, which is actually one of main obstacles that impedes the application of magnesium alloys in practical environments. Therefore, the protection is a major issue for research and development of magnesium alloys.Based on the advantages of magnesium alloys and their potentially widespread applications, the process of non-chrome chemical conversion on magnesium alloys is study in this dissertation, conversion film which has good corrosion resistance has been obtained, the influence of pH value on conversion film in corrosion resistance, and forming film mechanism. The specimens have been coated, and property of organic coating has been study.Magnesium alloys have been processed by non-chrome Phosphate- permanganate, and different conversion films have been obtained in different pH value. The macrograph,micrograph,chemical composition,phase status,property of corrosion resistance and binding strength have been tested and analyzed by metallogrophy,scanning electron microscopy(SEM),energy dispersive spectrometer (EDS),X-ray diffraction (XRD),X-ray photo- electron spectroscopy (XPS),corrosion weight-loss and testile test.AZ91D magnesium alloys processed have been immersed in 3.5% NaCl solution, corrosion resistance of conversion film varies from height to low with rising pH value, and its corrosion resistance is better than DOW7 when pH value is between 4 and 5.It is tested that the film, which the compositions of are distributed well, is amorphous, including elements of Mg,Al,Mn,O, comprised of MgO,Mg(OH)2,MgAl2O4,Al2O3,Al(OH)3,MnO2.AZ91D magnesium alloy is protected perfectly by MgAl2O4,Al2O3,MnO2. The reticular crackle, which can make the coating adhere to each other without process, can be observed. The pH value of Phosphate-permanganate conversion solution is an important influence on corrosion resistance of conversion film. However, corrosion resistance of conversion film on AZ31 magnesium alloy is too poor, which corrosion rate of is higher than AZ91D. AZ31 is not protected well. Because the conversion film on AZ31 is distributed uncontinuously, and they form galvanic corrosion. Subsequently, AZ91D converted was coated by organic matter, compared by contrast experiment to Q235.The adhesion between organic coating and former is better than latter. It is tested by SEM that organic coating is distributed well on the fracture. It is made further confirmation that AZ91D processed by non-chrome chemical conversion provide a good substrate for organic coating.
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