Study On TC4 Titanium Alloy Micro-arc Oxidation Preparation Process And Coating Sealing Technology

Micro-arc oxidation treatment is beneficial to enhance the corrosion resistance of the material.However,due to the characteristics of micro-arc oxidation coating formation,there are a large number of discharge holes appearing in the prepared coating,which provides convenience for the invasion of corrosive media.Therefore,it is necessary to study the micro-arc oxidation process and film sealing technology to further improve the corrosion resistance of the material by reducing the coating holes.At present,the influence of process parameters on the structure and performance of titanium alloy micro-arc oxide coating is not comprehensive enough,and the domestic and foreign researches on the sealing technology of titanium alloy micro-arc oxidation coating are mostly combined with complex processes,such as magnetron sputtering.In order to solve this problem,TC4 titanium alloy was selected in this paper.By the means of electrochemical impedance spectroscopy,dynamic potential polarization curve,contact angle test,XRD,SEM/EDS and infrared spectroscopy,the effect of micro-arc oxidation process parameters on the coating structure and corrosion resistance was studied in detail,and the changes in coating structure and properties were studied after sealing by two simple processes with stearic acid and BTESPT silane either.The results show that the corrosion resistance of the coating is closely related to the surface porosity of the coating.To achieve the purpose of improving the corrosion resistance of coating,increasing the pulse frequency properly,reducing the current density and duty cycle,and selecting the appropriate oxidation time are beneficial to the preparation of micro-arc oxidation coating with a smaller surface porosity.After sealing by stearic acid or BTESPT silane,the pores of the coating can be effectively closed,and the hydrophobicity of the coating surface can be improved.Compared with the untreated micro-arc oxidation coating,the coating after stearic acid or silane sealing treatment showed lower corrosion current density and higher resistance value,and the corrosion resistance of the coating was obviously improved.The result indicates that both stearic acid treatment and silane treatment are effective surface treatment methods,process is simple and the effect is obvious.It provides an idea for simplifying the micro-arc oxidation film sealing process and is beneficial to broadening the application range of micro-arc oxidation technology.