Preparation And Formation Mechanism Of Black Ceramic Coating By Micro Arc Oxidation On6063Aluminum Alloy

Aluminum alloy is widely applied to engineering field due to its outstanding specificstrength, thermal conductivity, electrical conductivity, no magnetic, easily forming, makingand recycling, etc. However, its lower surface hardness and poor corrosion resistance limit itsscope of application. So, it is important to improve its engineering properties by surfacetreatment on aluminum alloy.Micro-arc oxidation technology is a new surface ceramic treatment technology of Alalloy, The coating prepared by micro-arc oxidation with excellent hardness, corrosionresistance, stable color and well-adhered with aluminum and its alloy. Black ceramic coatinghave broad application prospect in protection of material, decoration and optical propertiesdue to ceramic properties and special optical properties.Black ceramic coating process has been developed by micro-arc oxidation on6063aluminum alloy in an electrolyte system containing Na2SiO3, Na3PO4, A, NH4VO4andadditives. Through the single factor experiment and orthogonal tests optimization electrolyteand electric parameters, finally obtained optimal technology parameters of black MAOcoating. The influences of technology parameters on micro-arc oxidation process andperformance of black ceramic coatings were investigated, such as color value, chromaticaberration, surface roughness and adhesion.SEM, EDS, XRD, XPS, Spectrophotometer, Auto Lab electrochemical workstation,Electrochemical polarization test, Neutral salt spray test and other means of measurementwere used to characterize the surface and section morphology, composition, microstructure,blackness, corrosion resistance of ceramic coating. The results were shown that the blackceramic coating has smooth surface and uniform color. Black MAO ceramic coating is dense,no obvious hierarchical structure, a few discharge pores were found on the coating surface. Thecoating mainly composed of amorphous or microcrystal oxides except of a small amount ofAl2O3and W. The formation of Vanadium oxide, W and Tungsten oxide result in the blackcolor of ceramic layer. The polarization curve shown that corrosion current density of blackceramic coating was0.00071μA/cm2, four orders of magnitude lower than that of the bared alloy (5.248μA/cm2), a little of corrosion spot appeared after774h neutral salt spray test,which reveal that corrosion resistance of black ceramic coating formed on6063aluminumalloys by MAO is significantly improved.