The electrolyte of traditional magnesium alloy anodizing generally contains elements such as chromium, fluorine and phosphorus, which not only pollutes the environment, but also harms human health. In recent years, compared with the classic processes Dow 17 and HAE, the corrosion resistance of oxide films obtained by environmentally friendly processes has been greatly improved. The excellent corrosion resistance comes from the uniform distribution of Al, Si and other elements on its surface after anodic oxidation, which makes the formed oxide film have good compactness and integrity.

It is generally believed that the porosity in the oxide film is the main factor affecting the corrosion resistance of magnesium alloys. It is found that the thickness, density and porosity of the oxide film can be improved to some extent by adding appropriate amount of silica-alumina sol into the anodic oxidation solution.

Moreover, the composition of the sol will increase the film-forming speed rapidly and slowly in stages, but it will not affect the X-ray diffraction phase structure of the film. However, the anodic oxide film is fragile and porous, so it is difficult to obtain a uniform oxide film on complex workpieces.

Extended data

Magnesium alloys have attracted much attention because of their small volume and mass, high specific strength, good machinability, good electromagnetic shielding, good vibration damping, good electrical conductivity and thermal conductivity. Magnesium alloys have been widely used in automobile materials, optical instruments, electronic communication, military industry and so on from the early aerospace industry to the present.

However, the chemical stability of magnesium is low, the electrode potential is very negative, and the wear resistance, hardness and high temperature resistance of magnesium alloy are also poor. This restricts the wide application of magnesium alloy materials to a certain extent. Therefore, how to improve the comprehensive properties of magnesium alloys, such as strength, hardness, wear resistance, heat resistance and corrosion resistance, and carry out appropriate surface strengthening has become an important topic in the development of materials.

Magnesium alloy is one of the lightest metal structural materials, and its density is only1.3g/cm3 ~1.9g/cm3, which is about 2/3 of that of al and 1/4 of that of Fe. Magnesium alloy has high specific strength, high specific stiffness, good shock absorption, electrical conductivity, thermal conductivity, electromagnetic shielding and dimensional stability, and is easy to recycle.

Known as the most promising green material in 2 1 century for its light weight and excellent comprehensive performance, it is widely used in aerospace, automobile manufacturing, electronic communication and other fields. However, the high chemical and electrochemical activity of magnesium alloy seriously restricts its application. Proper surface treatment can improve the corrosion resistance of magnesium alloys.

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