A Study On The Self-sealing ZrO₂ Ceramic Coating Preparation Of Applied Electric Field-micro-arc Oxidation On Mg Alloy

In recent years, Micro-arc oxidation(MAO) technology is the most favorable method in the surface treatment of magnesium alloys. With the treatment, the wear resistance, corrosion resistance, mechanical strength, and electrical insulation of the metals and their alloys can be effectively improved. Because the exist microcosmic discharge channels in the MAO ceramic coatings, through which corrosion medium can reach the ceramic membrane inside, and then further the magnesium alloy substrate, causing corrosion of magnesium alloys destruction.Therefore, in order to slow down the corrosion, in addition to the micro-arc oxidation ceramic film corrosion ingredients added, the more important method is made the micro-arc oxidation ceramic membrane pores effectively closed.In this paper, using Micro-arc oxidation-Applied electric field technology lining-up the self sealing type Micro-arc oxidation ceramic film on the surface of magnesium alloy.meanwhile change the pH value, generating Zr(OH) 4 colloids, through the drive of the electric field make the colloidal particles in magnesium alloy micro-arc oxidation membrane surface pores enrichment and participate plasma spark discharge, sintering, to film growth and pore closed once completed. By SEM(scanning electron microscope), EDS(EDS element mapping analysis) and potention dynamic electrochemical corrosion test analyse the closed micro-arc oxidation film microstructure and elemental composition of the sealing material and corrosion resistance.The results show that the surface of porous of micro-arc oxidation film is effectively closed, sealing material mainly constitute four Zr, O, Mg, F, compared to the unsealed micro-arc oxidation film, the closed the maintenance of corrosion oxide film remarkably improved. XRD results show that ZrO2 is the main phase in the films produced in Zr solution.This indicates that the zirconium added in the solution has diffused into the films through complex Micro-arc oxidation-Applied electric field. The existence of ZrO2 phase results in the high hardness of the films. With the applied electric field voltage increasing, the driving force increasing more Zr(OH) 4 colloids move into the hole, participate in plasma discharge 、sintering, which made the hole structure more compact, the film corrosion resistance improved. In addition, as time goes on, the film thickness increases, also improved the corrosion resistance.