| Magnesium alloy is the lightest structural metallic materials in practical applications, withspecific strength, high stiffness, and excellent machinability and damping performance, such as inaerospace, automotive, electronics and3C, and other fields have broad application prospects, andwas known as the richest potential development and application of "green engineering materials"in the21st century. However, magnesium alloys’ poor corrosion resistance has limited the furtherexpansion of its applications. Therefore, the research based on improving the protectionperformance of magnesium alloy surface, prolong the service life of the anodic oxidation processand corrosion behavior of magnesium alloys has the vital significance. Anodic oxide as a newtechnology on the ceramic surface of material, has simple process and low production cost, andfor porous structure, it can be used for decorative and protective purposes, and can effectivelyimprove the corrosion performance of magnesium alloy.On the basis of a broad investigation to the related literature at home and abroad, this paperhas summarized the research status of the magnesium alloy anodic oxidation process and therelated basic theory, and using magnesium alloy as raw materials, mainly from the developmentdoes not contain chromium, fluoride and phosphorus non-toxic harmless green anode oxidationprocess, and the factors affecting the performance of magnesium alloy anodic oxidation film hascarried on the preliminary study, and the surface observation technology has potentiodynamicpolarization curve, the detection means for all wetted experiment, scanning electron microscopy,electronic energy spectrum,and so on.Selectiing NaOH, Na2SiO3, Na2B4O7, Na2CO3as the main component of anodic oxidationelectrolyte, and using the orthogonal experiment method and poor analysis to determine the bestelectrolyte anodic oxidation. The results showed that the best electrolyte anodic oxidation has50g/L sodium hydroxide,100g/L sodium borate,20g/L sodium silicate,30g/L sodium carbonate.On the basis of having determined the electrolyte composition, studying other anodicoxidation parameters on the influence of the oxide film formation.The results showed: theoptimum technological parameters was: at room temperature, oxidation time was15min, workingvoltage was60V, pulse frequency was200Hz. And the longer oxidation time, the larger workingvoltage, the thicker the oxide film, but when the parameter value is too large, the formation ofrough surface oxidation film, corrosion resistance decrease. However, the pulse frequency just onthe opposite. When the pulse frequency was more than400Hz, the oxide film was transparent andthin.At the same time, by scanning electron microscope to observe the surface morphology ofanodic oxide film, and using coating thickness gauge to measure the thickness of oxide film,and through EDS analyzing layer membrane elements. The results showed that,after optimizationprocess, the oxide film thickness was about15μm, and has excellent adhesion with magnesiumalloy matrix, and having good appearance, uniform density, better corrosion resistance; Judgingfrom the microstructure, oxide film had porous structure, which can provide a good base for orderprocessing after, and make order after coating processing more and more strong, such as adhesionon it; Oxide film is a kind of composite ceramic membrane, and the elements of it were C, O, B,Mg and Si. The existence of elements C, Si and B showed that, in the process of anodic oxidation,electrolyte had taken part in film-forming process or changed the film-forming process, andeffective form part of the oxide film;... |
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