Research On Preparation And Properties Of Self-healing Coating On Mg Alloys

The organic coating which is one of the methods to improve the corrosion resistance performance is the most effective method with the advantages of low cost,simple preparation process,good protective performance and low reactivity with metal substrate,etc.But the difference of chemical properties between the organic coating and metal substrate greatly reduces the bonding force,which shortens the lifetime of coatings with the appearance of defects in the coatings.Therefore,silane coupling agent technology and self-healing technology solved this problems well.In this paper,silane coupling agent was used as the Mg alloy surface treatment agent firstly.And then,the organic-inorganic composite coating with the certain self-healing function was prepared on the surface of silane treated Mg alloy substrate by sol-gel method.The self-healing properties of the composite coating was also investigated.In this paper,the surface treatment agents used on Mg alloy surface were KH550 and KH570.The optimum hydrolyzation conditions were obtained by single factor experiments.The optimum hydrolyzation conditions of KH550 were showed as:volume concentration,10%;solvent,ethanol;hydrolysis temperature,40℃;hydrolysis time,18 h.The optimum hydrolyzation conditions of KH570 were showed as:volume concentration,5%;solvent,methanol;hydrolysis temperature,room temperature;hydrolysis time,15¹8 h.The anticorrosion property of KH550 and KH570 silane film prepared under optimum conditions was studied.The results showed that the corrosion resistance of KH570 silane film was better,and the corrosion current density was 1.647×10-5 A·cm^-2,and the corrosion potential was-1.469 V.The influence of rare earth element La on the protective properties of the KH570 silane coating was studied by FTIR、SEM and electrochemistry tests.The results showed that the corrosion resistance of the KH570 film was decreased obviously as the increase of the concentration of La³⁺.The optimum addition of La³⁺in this experiment was 5×10^-4 mol·L^-1,and the corrosion current density was 0.192μA·cm^-2,and the corrosion inhibitory efficiency for the Mg alloy was up to 95.8%.Ordered mesoporous SiO₂ nanoparticles was synthesized by sol-gel method.Furthermore,the obtained SiO2 nanocontainers were loaded with saturated acetone solution of corrosion inhibitors MBT under vacuum conditions.After that,the SiO2 loaded with MBT was added into epoxy resin,and then,an organic-inorganic composite coating was prepared on the surface of Mg alloy.The physicochemical properties and load capability of SiO2nanocontainers was performed by XRD,TEM,N2 adsorption isotherms and TGA,respectively.The results revealed that the SiO₂ nanocontainers were MCM-41 with hexagonal system,and the load amount of MBT was 83.7%.The influence of the addition amount of SiO2 nanocontainers on the protective properties of composite coatings was also studied.In addition,the self-healing property of the composite coating was investigated by artificial defect experiment,and the mechanism of self-healing was also discussed.The study of interfacial treatment and anticorrosion materials applied on magnesium alloy has very important theoretical significance and engineering application values.