Corrosion Resistance And Inorganic Hole Sealing Of Micro-arc Oxidation Films On Magnesium Alloy

Micro-arc oxidation technology can effectively improve the surface corrosion resistance and abrasive resistance of magnesium alloy.As the micro-arc oxidation process on magnesium alloy needs further improvement,and hole sealing treatment has significant effect on improving corrosion resistance of micro-arc oxidation films,the research and discussion has been conducted about corrosion resistance of micro-arc oxidation films and hole sealing treatment.AZ91D magnesium alloy was used to be treated with micro-arc oxidation process.Some main working achievements are as follows:1.For the consideration of the thickness of the films,the corrosion resistance and environmental protection,sodium aluminate was chosen as the main salt of the electrolyte,and 30%H2O2 was chosen based on the exclusion of Na2EDTA,sodium tartrate,glycerin as the addictive.Finally the composition of electrolyte was determined by controlling single component of electrolyte as a variable,the component of electrolyte is NaAlO2 15g/L,NaOH 10g/L,30%H2O2 3ml/L;2.Microstructure and phase composition of films were examined by SEM and XRD,the micro-arc oxidation films are uniform and compact,and their main phase consists of MgO and MgAl2O4;the thickness of micro-are oxidation films increase as the increase of voltage and concentration of 30%H2O2,it will also increase as the time of treatment extends,frequency has very little influence on thickness of the films;3.The corrosion resistance of both the magnesium alloys and micro-arc oxidation samples were tested by electrochemical analysis to study their corrosion mechanisms.The results show that micro-arc oxidation can improve the corrosion resistance of the magnesium alloys and the E,oor of samples enhance 336mV after being micro-arc oxidation treated.The corrosion resistance of the films increases first then declines as the increase of voltage,frequency and concentration of 30%H2O2 and the extension of time;4.The abrasion resistance of micro-arc oxidation films under the condition of lubrication was studied;the curves of the relationship between the films’ frictional factor and wear rate and the different voltage,time,frequency and concentration of 30%H2O2 were acquired.So the regularity of how the above process parameters influence the wear resistance of the films was concluded.5.The corrosion resistance and wear resistance of the micro-arc oxidation films treated with hole sealing process was studied,and the results show that inorganic hole sealing process can improve the corrosion resistance of the films,the Icorr reduces one order of magnitude.The results of electrochemical analysis and hydrochloric acid immersion test show that the effect of nickel sulfate hole sealing treatment is better;the film has not been corroded by hydrochloric acid after being immersed for 5 hours.However the hole sealing treatment has little influence on wear resistance of the films.