The Preparation Technology Of Microarc Oxidation Coating For Magnesium And Study Of Coating Corrosion-resistance

The constitutes of microarc oxidation treating solution formulae for magnesium as silicate, phosphate, hexad partial phosphate and carbonate system and the effect of treating process on the properties of ceramic coating were studied systematically using contrast and orthogonal experiment. By SEM, XRD and EPA, the growing characteristic of microarc oxidation ceramic coating for magnesium was observed; the phase constitutes of ceramic coating and element distribution in various thickness were measured; the major factors affecting the corrosion-resistance of ceramic coating were analyzed.The formulaes such as phosphate, silicate and hexad partial phosphate system have been optimized,and the better formulae and its process parameter have been developed on the base. The results indicated that the ceramic coating for magnesium was made up of loose coating ,compact coating and transition coating. The parameters as oxidation time, current density, occupy-empty ratio of current, current frequency, electrolyte constitutes and temperature had obvious influence on the quality and corrosion-resistance of ceramic coating. It was found that the compactness, thickness and phase constitute of coating was inner factors affecting corrosion-resistance from structure observation, in which the-n-compactness is the best key factor. The process parameters were only outer factor affecting corrosion-resistance. The microarc oxidation ceramic coating was mostly made up of MgO, MgAl2O4 and amorphism phase, whose contents varied with different conditions and positions. The content of amorphism phase exceeded 80%,which best content could reach 95%.