As structural materials, magnesium and its alloys have excellent properties such as low density, high strength and non-toxicity, but their corrosion resistance is poor, and many applications are limited. At present, there are many methods to control the degradation rate of magnesium alloys, and micro-arc oxidation composite film is an effective and economical means.
Magnesium alloy micro-arc oxidation technology refers to the technology of in-situ growth of porous thin films with porous structures on the surface of non-ferrous metals with the help of micro-spark discharge on the surface of the matrix. The micro-arc oxide film has the advantages of good adhesion, corrosion resistance, wear resistance, biological anti-corrosion, high temperature impact resistance, and low dielectric Changshu. Micro-arc oxidation technology is one of the commonly used surface treatment technologies for magnesium, aluminum, titanium and other metals and their alloys, which can control the oxide thickness, electrochemical composition, pore size and roughness of magnesium alloy micro-arc oxide film. Microarc oxidation
The micro-arc oxide film includes an inner dense layer and an outer porous layer, the inner layer is a physical shield of the corrosive medium, and the microporous and microporous cracks of the outer layer can enhance the adhesion of organic matter or polymer on the film. At present, the density of the film layer is improved by adjusting the micro-arc oxidation process or the post-treatment of the micro-arc oxide film, so as to improve its corrosion resistance, while the research on the adjustment of the micro-arc oxidation process is mostly focused on the adjustment of electrical parameters and electrolyte composition, and the post-treatment of the micro-arc oxide film is to further improve the performance of the micro-arc oxide film through the traditional sealing or composite film process. Because the micropores and microcracks in the outer layer of the micro-arc oxide film provide mechanical interlocking sites for organic matter or polymers, composite films with good structure and corrosion resistance can be developed on the basis of magnesium alloy micro-arc oxide films, which can be combined with low-friction layers or lubricating films, including hydrophobic films, electroless plating, diamond-like films and hard coatings.
In recent years, although magnesium alloy micro-arc oxidation has developed rapidly, the magnesium alloy micro-arc oxide film is prone to micropores and microcracks to reduce the corrosion resistance of magnesium alloy, and there are still problems such as the lack of large-scale magnesium alloy micro-arc oxidation industrial production lines in China, and the failure of a single magnesium alloy micro-arc oxidation to meet the actual requirements, complex process and high cost.
Therefore, from a technical point of view, strengthening the development of magnesium alloy surface treatment technology and in-depth study of the formation mechanism of protective film can further improve the performance of surface protective film to solve the pain point of magnesium alloy corrosion, which has great practical significance and economic benefits in promoting the application of magnesium alloy materials in aerospace, transportation and electronics industry in the field of industrial application.
Composite oxidation technology is a kind of magnesium alloy surface treatment technology developed for the corrosion resistance, wear resistance, high temperature resistance and other performance problems of magnesium alloy materials, the process perfectly optimizes these problems, composite oxidation technology is the latest technology developed after the surface treatment of magnesium alloys such as electroless plating, conversion coating, anodizing, organic coating, thermal spraying and vapor phase treatment.
Magnesium alloy composite oxidation technology has the characteristics of simple process and wide adaptability of materials, the obtained film layer is uniform and hard, which can play a long-term protective role, the salt spray time can reach 200 hours, and the combination of coating and matrix is tight, which is also an important breakthrough in the development of magnesium alloy surface treatment technology.
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