Study On The Preparation And Performance Of Microarc And Electrophoresis Composite Film On Aluminum Alloy

A new composite film was prepared by formed a dense and porous oxide ceramic layer by microarc oxidation firstly and then deposited an electrophoresis layer on the former, namely, a microarc and electrophoresis composite film was prepared. The surface and cross-section morphologies of composite film were observed by SEM and the element distribution along cross-section was analyzed by EDS. The effects of microarc oxidation parameters and electrophoresis parameters on the quality of composite film were investigated. The effect of oxidation parameters and electrophoresis parameters on the corrosion resistance of composite films was investigated by immersion testing and electrochemical analysis, respectively. Then, the resistance mechanism was analyzed. The corrosion resistance of microarc and electrophoresis composite film was compared with the traditional electrophoresis. The effects of oxidation parameters and electrophoresis parameters on cohesion property between film and substrate was investigated by cross cut test.The results indicate that the possibility of the proceeding of microarc and electrophoresis and the roughness of the composite film were influenced by oxidation parameter and electrophoresis parameter. The proceeding of the composite treatment was determined by oxidation voltage, oxidation time and electrophoresis voltage. When oxidation voltage 500V, oxidation time 10min and electrophoresis voltage 60V, the driving force of electrophoresis particle was very small, as a result, the composite treatment was difficult to proceeding or the roughness of film was bad. Excellent films with well roughness were prepared at oxidation voltage 450V, oxidation time 5min, electrophoresis voltage 170V, oxidation frequency 700Hz and oxidation duty cycle 8%. The corrosion resistance of composite film was influenced by oxidation parameter and electrophoresis parameter. As the increase of frequency and duty cycle, the corrosion resistance of composite film was elevate. The film prepared at electrophoresis voltage 170V and electrophoresis time 3min presents excellent corrosion resistance. The corrosion resistance of composite film prepared by optimal parameter was good than traditional treatment. The cohesion between composite film and substrate was influenced by oxidation frequency and duty cycle. The optimal cohesion was obtained at oxidation frequency 400～ 700Hz,duty cycle 8～24%. The composite film which prepared by the optimal parameter presented excellent cohesion with substrate.