| With the improvement of social environmental awareness,highly polluting chromate conversion process is gradually withdrawing from the stage of surface treatment technology of aluminum,and the environment-friendly silane technology came into being,it was more and more concerned with the advantage of simple process,low consumption,no toxic solution,high corrosion resistance,and was entrusted with the task to replace the chromate conversion treatment.However,the application of silane processing technology was limited because of the traditional single function of silane film,poor mechanical performances and does not have the"self-healing" capacity.The experiments,focus on the defection of the traditional silane technology,we prepared a composite silane film on the surface of aluminum,and combined with the advantages of rare earth conversion coating,we added cerium(Ⅲ)nitrate hexahydrate to silane film in oeder to get a high mechanical strength and self-healing film.The silane treatment solution for the surface pretreatment of aluminum alloy was prepared by mixing γ-(2,3-epoxypropoxy)propytrimethoxysilane and n-Propyltrimethoxysilane.By monitoring the electrical conductivity of the solution during the hydrolysis process,and using the control variable method to studied the influence of factors on the hydrolysis process of composite silane solution,and the results showed that the optimum hydrolysis system of mixed silane solution were:the amount of methanol was 15%,the concentration of silane coupling agent was 8%,the hydrolyzate PH was 6 and the the hydrolysis temperature was 30℃.The silane solution with the equilibrium of hydrolysis was used in the surface treatment process of aluminum alloy.By optimizing the conditions such as silane concentration,curing temperature and film forming time,a composite film was prepared on the surface of the substrate.The results show that the composite silane film prepared with KH560:PTMS 1:2 treatment solution at 150 ℃ for 1.5h has the best performance.The infrared spectroscopy test revealed the formation mechanism of the film.By comparing with different film samples for corrosion resistance and mechanical testing,we intuitively evaluated the comprehensive performance of the composite silane film,among them,The electrochemical test showed that the corrosion current of the composite silane film was1.641×10^-8A/cm2 which was decreased by 1 order of magnitude compared with that of the single layer,and was 2 orders of magnitude lower than that of the blank sample;The contact angle test showed that the contact angle of the composite film with water was 91.5°,which was higher than that of other samples;And the SEM scan of the film surface shows that the composite silane film is more uniform and dense.The cerium nitrate was used to modify the composite silane film,and a hybrid silane film with self-repair ability was prepared on the surface of aluminum alloy.We studied the influenceof the addition of cerium salt on the film forming process,and the results showed that the composite silane treated with 0.5 g of cerium nitrate was cured at 180 ℃ for 1.0 h,and the chemical resistance and mechanical properties was the best.There was no absorption peak associated with cerium in the infrared spectrum,indicating that the cerium nitrate was not react with the silane coupling agent.The white granular material appeared in the SEM scan of the hybrid film contained element Ce was analyzed by EDS,And the absorption peak of cerium oxide appears in the XRD test results,indicating that cerium is filled in the network structure of the silane film in the form of its oxide during the film formation of the hybrid film.The comparison between the hybrid film and the silane film shows that the corrosion resistance of the cerium nitrate is improved intuitively.The salt spray test proves the self-repairing ability of the hybrid film... |
