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Micro-arc oxidation coloring can be obtained in the non-ferrous metal surface with good corrosion resistance , color uniformity and stability of the ceramic layer , significantly improve the non-ferrous metal corrosion and decorative breakthrough in the presence of magnesium alloy surface shading technology many of the problems , and has broad application prospects . This paper studies the colored liquid formulations of micro-arc oxidation of AZ91D magnesium alloy in silicate system , in the fixed electrical parameters on the basis of using a single factor experimental method of formulation component coloring film . By means of SEM, EDS, XRD material analysis method to observe the surface morphology of the ceramic layer , and determination of the phase composition and elemental distribution of the ceramic layer , and explore the various components of the mechanism . Studies have shown that , the the metavanadate add the right amount of silicate system , good corrosion resistance , uniform color brown yellow ceramic coating , but the concentration of large more than 8g / l , the surface of the larger defects , The pore size increases, the corrosion resistance decreased , the surface quality . Add an appropriate amount of phenol , the film thickness , and the corrosion resistance is increased , darker , but the concentration is too large when more than 8g / l , the surface of microcracks and gray pitting, resulting in deterioration of film performance , another EDS and XRD tests found that the film in the presence of the objects of C , which illustrates C is also involved in micro-arc oxidation reaction of the carbonate to make the film is grayed out . Silicate and sodium hydroxide added to increase the conductivity of the solution , reducing the breakdown voltage , and promote the passivation film deposition , the film thickness increases rapidly , to improve the surface state of the film , but the content is too high , and a negative impact on the film . Glycerol added , reducing the tip discharge , stability of the electrolyte , and to improve the thickness of the film and corrosion resistance and good film properties . Brown film XRD analysis showed that the layer containing the V3 or V5 phase VO3- anions into the discharge channel thermochemical physical reactions are involved , generate vanadate their oxides , deposited in the discharge channel bottom , leaving the film presents some yellow .
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