Study Of The Preparation And Performance Of Powder Composite Micro-arc Oxidation On Magnesium Alloys

Magnesium alloy was widely applied in various fields because of its excellent properties. However, the low corrosion resistance has impaired the widespread application of the magnesium alloys. The surface treatment was needed. MAO uses the spark discharge to generate ceramic oxide film on the surface ofmagnesium alloys. The corrosion resistance and strength of film was improved. This article used joining powder into electrolyte to form composite film on the surface of AZ91 D magnesium alloy. The effect of different powder on the performance of composite micro-arc oxidation film was researched. The SEM, XRD, the Tafel, drop test and other testing methods were used to test the performance of the composite film.Joining Ba Zn2Fe16O27 powder which was made by the sol-gel method into the electrolyte of micro-arc oxidation, the composite micro-arc oxide film was prepared on the surface of the magnesium alloy. The effect of electrolyte composition, powder amount, the magnetic field on the performance of composite micro-arc oxidation film was researched, and the best formula of the basis electrolyte and the addition amount of powder was optimized. Results showed that after adding nano Ba Zn2Fe16O27 powder, the holes and cracks on the surface of the film decreased, the Ba Zn2Fe16O27 phase increased, the content of Fe, Ba, Zn in the film significantly increased, the corrosion potential of composite film was raised to-0.869 V from-1.089V(the corrosion potential of micro-arc oxidation film), the corrosion current of composite film was reduced to 2.95×10-7A from 2.26×10-6A, the corrosion resistance was obviously improved. Adding magnetic field condition could contribute to the content of Ba Zn2Fe16O27 powder in the composite film and improve the corrosion resistance of composite film, the corrosion potential of composite film was raised to-0.813 V from-0.869 V, the corrosion current was reduced to 1.86×10-7A from 2.95×10-7A.Adding nickel powder which was made by liquid phase reduction method into the electrolyte of micro-arc oxidation, the composite micro-arc oxide film was prepared on the surface of the magnesium alloy. The effect of addition amount of powder on the surface morphology and structure of composite micro-arc oxidation film was researched, and the best addition amount of powder was optimized. The effect of addition of glycerol and sealing experiment on the performance of composite film were also analyzed. Results showed that after adding nano nickel powder, the holes and cracks on the surface of the film decreased, the Ni phase increased, the corrosion potential of composite film was raised to-0.843 V from-1.089V(the corrosion potential of micro-arc oxidation film), the corrosion current of composite film was reduced to 4.682×10-7A from 2.26×10-6A, the corrosion resistance was obviously improved. The additions of glycerine made the micro-arc oxidation reaction more stable, the discharge apertures of the composite film were smaller and the compactness and the anti-corrosion ability of the film were increased, the corrosion potential of composite film was raised to-0.832 V from-0.843 V, the corrosion current of composite film was reduced to 1.436×10-7A from 4.682×10-7A. The sealing experiment could reduce the holes and improve the corrosion resistance.Nickel coated Si C powder was prepared by chemical plating method. Adding Nickel coated Si C powder into the electrolyte of micro-arc oxidation, the composite micro-arc oxide film was prepared on the surface of the magnesium alloy. The effect of addition amount of powder on the surface morphology and structure of composite micro-arc oxidation film was researched, and the best addition amount of powder was optimized. The effect of ultrasonic oscillation and sealing experiment on the performance of composite film were also analyzed. Results showed that after adding nickel coated Si C powder, the holes and cracks on the surface of the film decreased, the corrosion potential of composite film was raised to-0.913 V from-1.089V(the corrosion potential of micro-arc oxidation film), the corrosion current of composite film was reduced to 1.548×10-6A from 2.26×10-6A, the corrosion resistance was obviously improved. The ultrasonic oscillation condition could contribute to the content of nickel coated Si C powder in the composite film and improve the corrosion resistance of composite film, the corrosion potential of composite film was raised to-0.902 V from-0.913 V, and the corrosion current was reduced to 1.86×10-7A from 1.548×10-6A. The sealing experiment could reduce the holes and improve the corrosion resistance.