Research On Magnesium Alloy Surface Treatment With AC Micro-arc Oxidation

At present, micro-oxidation treatment technology is a good idea for the surface treatment technology of magnesium alloy. The ceramic coating which has quality can be generation on the surface of magnesium within this technology, and it can significantly improve the corrosion resistance of magnesium alloy. But The technology of processing efficiency is not high, processing time is usually in 15-90 minutes. In order to improve the efficiency of micro-arc oxidation, Magnesium alloy, we have embarked on the research of magnesium alloy surface treatment with AC micro-arc oxidation, and studied the process of micro-arc oxidation of AZ91D magnesium alloy in alkaline solution systems. The morphology and microstructure of the coating were observed through SEM, XRD techniques. The effects of processing parameters including electrolyte concentration, output voltage, electrolyte temperature and treating time on the growth and properties of micro-arc oxidation coating were investigated. And the use of immersion test, acid drip experiment to study the corrosion resistance of the coating. The linear formula is concluded as follows:During the process of micro-arc oxidation, experiment results show that the ceramic coating in the surface of magnesium alloy is mainly compose of MgO phase and MgF₂ phase, parameters in the process of micro-arc oxidation such as electrolyte concentration, electrolyte temperature and oxidation time have the existence of non-linear relationship between the ceramic coating; When oxidizing at constant frequency, the parameters had an optimum point. Over or below the point, the ceramic coating quality was degraded..During the process of micro-arc oxidation, according to orthogonal experiments, the optimum formulation for the solution system which has better combination of strength ceramic coating, corrosion resistance was determined by the thickness of ceramic coating and the acid dripping test time: KOH360g/l, KF₂1000g/l.In this study, the time for the process of micro-arc oxidation of magnesium alloy was reduce to less than 1 minutes, greatly improve the efficiency of micro-arc oxidation treatment., the research results about the surface treatment technology of magnesium alloy have lay the foundation for the use in the industry.