Research On Environmental-friendly Silane Coating On Steel Surface

Technique of silicon alkylation treatment on the surface of metal is a new green technology,and it is one of the most hopeful way to instead of the process of phosphating and chromizing.The process of silicon alkylation is pollution-free,simple,low-cost,ect.40 Cr alloy steel passivated by silane is rare,and the protection to metal of the traditional silicon alkylation process is limited,This article explored thetreatment of silicon alkylation on the surface of 40 Cr alloy steeland modifing the silane solution.In the article,BTESPT was selected as the main agent of silane fluid, with ethanol as main solvent,acetic acid and ammonia asthe regulator of pH,suitable amount of water to promote hydrolysis of silane.Single factor experiments with eight major factors which affect the hydrolysis of silane and shaping film was carried out,and the optimum range of the etight factors’ values were obtained.Selecting optimum values from the range of the values ofsingle factors,by two-step orthogonal test,the best technology of silane treatment was obtained.After 72 h hydrolysis,through the infrared spectrum analysis of the silane solution,the result showed that the condensation reaction and hydrolysis reaction of silane had happened and Si-O-Si and Si-OH shaped.The analysis of surface morphology and composition of the silane film by SEM and EDS has proved that the metal surface had formed dense silane film.XPS analysised the elements of surface and the form of the elements,the result showed that the surface of the silane film may exist with Si-O-Si,C-H,Si-CandC-Ofoim and-O-C2H5 and Si-OH groups which were not hydrolyzed.Through the copper sulfate titration test, salt spray weightless test,Salt water immersion test,sour alkali soak test of the BTESPT silane film,the corrosion resistance was analyzed and compared,coming to the conclusion that the silane of BTESPT had as goodcorrosion resistance as the film of zinc phosphating.By Tafel curve and electrochemical impedance spectroscopy,the electrochemical properties of the silane film were analyzed,The tests had the conclusion that BTESPT silane treatment of 40 Cr sample was anode corrosion polarization controling process and silane film.And silane film had mianly physical protection.In order to improve the performance of the silane film, zirconium fluoride sodium and TEOS were added in the silane solution.Two kinds of hybrid membrane were prepared and the process of mading hybrid membrane was optimized respectively by single factor test and orthogonal test.Based onSEM analysis,a number of uniform particles could be seen on the surface of hybrid membrane added sodium fluoride zirconate and these small particles filled in the micro pore of silane film. these micro particles may be chemical compound about Zr. Through the copper sulfate titration test, salt spray weightless test,Zr-silane hybrid filmis more slushing than the film of silane and phosphating.Through comparing the tafel curves,the conclusion showed that the hybrid membrane not only suppressed the reaction of anode corrosion,but the cathodic corrosion reaction was suppressed. Corrosion potential had shifted positively.EIS spectrum proved that the silane film mixed with zirconium fluoride acid sodiumhad improved the compactness.Through XPS,possible chemical valence state and form of Zr element on the surface of silane film was analyzed.Finally,according to tests of this paper,the modelof the hybrid membrane’ structure was put forward.Based on SEM analysis ofTEOS-silane hybrid,the morphology of the hybrid membrane could be saw and the surface of membrane layer was uneven.There were a few of small particles existing on the surface of the film,maybe the Nano silica formed.Through the copper sulfate titration test, salt spray weightless test,TEOS-silane hybrid filmis more slushing than the film of silane and phosphating. Tafel curves and EIS impedance graph showed that the density of silane film was greatly improved,after adding TEOS. According to tests of this paper,a model of the hybrid membrane’ structure was put forward.