Investigation On Silane Treatment Of Aluminum Alloy And Corrosion Behavior Of Film

Silanization treatment is a kind of surface treatment technology method which was prepared by polycondensation of silane hydrolysate and hydroxyl group on metal surface.Compared with traditional chemical conversion film technology（such as phosphating,chromate passivation,etc.）,it has advantages of simple operation,low cost,excellent performance and environmental protection.Therefore,it has a wide application prospection in the surface anti-corrosion treatment of metal material components in automobile,ship and aviation fields.To improve the corrosion resistance of silane film on the aluminum alloy,based on the fundamental BTSE silane process,the paper discussed the feasibility of silane doping modification process,compound silane process and double silane film technology.Furthermore,the paper focused on the corrosion behavior and corrosion resistance mechanism of various silane films.Firstly,6061 aluminum alloy was silanized by BTSE silane coupling agent.The effects of hydroxylation pretreatment process,silane hydrolysis process（alcohol-water ratio,silane concentration and hydrolysis time）,silane film curing process（curing temperature and curing time）on the corrosion resistance of the film were investigated.Then,the optimal process parameters were obtained and the complete and compact silane film was fabricated via the investigated optimal process.The results showed that hydroxylation pretreatment increased the content of hydroxyl compounds on the surface of aluminum alloy,which was conducive to the condensation reaction during silanization treatment.After silane treatment,the corrosion process of 6061 aluminum alloy changed from active dissolution state to passivation state,the corrosion current density decreased from 1.86×10^-6A·cm^-2to 5.51×10^-9A·cm^-2,the low-frequency impedance modulus increased from 6.47×10²Ω·cm²to 1.86×10⁶Ω·cm²,the corrosion resistance was also significantly improved;the scratch test showed that the BTSE silane film soaked in Na Cl solution had a certain self-repairing propertyBased on the study of the basic process of BTSE silanization,phytic acid,pentasulfosalicylic acid and Ce O₂ nanoparticles were selected in this paper to conduct doping modification of BTSE silanization process,and the optimal concentration of modifier was obtained through optimization experiments.After doping modification,the corrosion resistance of BTSE silane film modified were significantly improved.From the results of corrosion resistance evaluation,the BTSE film modified by PA has the best corrosion resistance property and the self-curing property.Combined with the results of XPS,FR-IR and FIB-TEM to conduct the investigation of the mechanism.It was found that phosphate group in phytic acid can chelate with trivalent aluminum and react with silanol to make the film more dense.Based on the research on the basic process of BTSE silanization,this paper also explored the composite silanization process to expect making advantages of different types of silane coupling agents to improve the corrosion resistance of silane film,finally,the BTSE-KH560-OTES（BKO）trisilane composite film was successfully prepared.The results indicated that the trisilane composite system made the breaking potential increasing to+0.467V/SHE,beyond that,the film had better corrosion resistance,adhesion,hydrophobicity,and excellent comprehensive performance.However,compared with BTSE silane film,the cyclic polarization results indicated that although the breaking potential increased,the protective potential changed not significantly.Furthermore,the hysteresis ring area increased,indicating that the self-healing performance of the composite film was not improved,the good corrosion resistance was mainly due to the physical shielding effectTo obtain self-healing performance and good physical shielding effect of the film layer simultaneously,based on the exploration and research of doping modified silanization and compound silanization processes,a bilayer silane film with BTSE silane film modified by PA as the bottom layer,the BKO composite silane film as the surface layer was successfully prepared.On the basis of the above,the dimensional blunt current of the bilayer membrane decreased more,and the breaking potential increased further to+0.561 V/SHE,the protection potential increased to-0.354 V/SCE.After 5000 h immersion in Na Cl solution,the low-frequency impedance modulus was still as high as 10⁶Ω·cm²,maintaining a good protective effect.