Magnesium Alloy Micro-arc Oxidation And Sol - Gel Surface Modification

The 21st century is the rapid development times for magnesium and alloys material, magnesium alloys have unique characteristics of low density, high strength-to-weight ratio, high rigidity and the abundant raw materials, and AZ91 is one of the most widely used as a magnesium alloy. However, the Magnesium is a very active metal, and the chemical stability of magnesium alloys is poor. In the service environment the magnesium alloy is very easy to be corroded, so poor corrosion resistance greatly limits the application of magnesium alloy. Now the corrosion resistance of magnesium alloys has become the focus of research at home or abroad, because it has a direct bearing on the future development and applications of magnesium alloys.Based on the summary of the corrosion characteristics of magnesium alloy and the surface modification technologies of magnesium alloy, this paper studied the change of corrosion resistance of Mg alloys by the micro-arc oxidation and sol-gel method.Micro-arc oxidation technique is the most favorable method in the surface treatment of magnesium alloys in recent years. With the treatment, the mechanical strength, corrosion resistance, wear resistance and electrical insulation of magnesium alloys can be effectively improved. The electrolyte of micro-arc oxidation is alkaline solution. In this study, we get an oxide ceramic layer on the surface of magnesium alloy in the silicate electrolyte. We studied the surface morphology, surface coating composition and corrosion resistance of magnesium alloy after treatment by using scanning electron microscopy, X-ray diffraction, energy disperse spectroscopy (EDS) and electrochemical polarization methods. The results show that after micro-arc oxidation treatment the corrosion resistance of magnesium alloys has been greatly improved.As the micro-arc oxidation process go with discharge phenomenon, there exist microcosmic discharge channels in the micro-arc oxidation ceramic coatings, through which corrosion medium can reach magnesium alloy substrate, resulting in corrosion. It is very necessary to perform sealing treatment to the micro-arc oxidation ceramic coatings. Sol-gel method is a relatively new surface treatment method for magnesium alloy. In this paper, it uses silica solution coating on magnesium alloy. After getting better coating process, it re-use sol-gel method to perform sealing treatment to the micro-arc oxidation ceramic coatings, which then received a composite coating of micro-arc and sol. Characterizing the surface film show that, the corrosion resistance are further improved through complex layers than the separate treatment of micro-arc oxidation.