Study On Preparation And Corrosion Resistance Of Micro-arc Oxidation Coatings Of Mg-2Zn-1Mn-0.5Ca Alloy

Magnesium and its alloy have excellent biocompatibility, they are widelyused in medical convenience. But magnesium in the periodic table of elements inrow IIA, more lively and easy corrosion, this greatly limits the application ofmagnesium alloy. In order to improve the corrosion resistance of magnesiumalloy, to further expand its scope of application. In this paper, Mg-2Zn-1Mn-0.5Ca biological magnesium alloy is researched, preparation of a corrosionresistant biological coating on the surface by Micro-arc Oxidation, research andoptimization of micro arc oxidation process and parameters of Mg-2Zn-1Mn-0.5Ca alloy, and further reveals the influence law of process parameters on thecoating corrosion resistance.NaOH, Na2SiO3, KF are slected as three basic components of theelectrolyte, at higher power frequency of1000Hz and the duty cycle of15%, bychanging oxidation voltage, oxidation time, additive content parameters toprepare different oxidation coating. Using SEM, XRD and other experimentalmethods to reveal the influence of different processing parameters on the coatingthickness, surface topography and phase composition. The results show that withthe increasing oxidation voltage, the coating thickness first increase and thendecrease, the micropore size of coating surface gradually decrease, but thedensity of the micropore continues to increase, the surface roughness graduallydecrease, when the voltage reaches a certain value, the coating will easily lead toa breakdown. With the increasing oxidation time, coating thickness continue toincrease, when reaching the equilibrium state, no further increase in coatingthickness. The addition of the additive make the coating thickness increasesignificantly, and with the increasing additive content, coating surface is more densification and smoothing.The affect of different technological parameters on the corrosion resistanceof coating was studied by drop test, simulated body fluid immersion and thepolarization curve test. It turns out that the corrosion resistance of coatingweakens after reaching a peak with the increasing of oxidation voltage, thethickness of coating has an influence on the corrosion resistance, which isconnected with oxidation time. At the same time, the corrosion resistanceincreased with the ascend of corrosion potential when the additive was added.When the Micro-arc Oxidation process parameters is oxidation voltage350V, the oxidation time10min, the addition of sodium benzoate content2g/L,micro-arc oxidation coatings of Mg-2Zn-1Mn-0.5Ca alloy is smooth and dense,no microscopic defects, after soaking in the SBF for four weeks, surface coatingis in good condition, coating degradation uniform under metallographicmicroscope, no substrate exposed, corrosion resistance is good.