Silane Coupling Agent Of Electro-assist Deposition And Its Application On The Carbon Steel Surface

As we all know,it is commonly known that corrosion is a conundrum worldwide,how to improve the corrosion protection of materials has always been a vital issue in the field of materials science.Strong biological toxicity and serious environmental pollution are two fatal flaws that exist in both phosphating technology and chromate passivation technology which are faced being eliminated.Silanization technology is expected to replace the traditional phosphating technology and chromate passivation technology,and it is fully consistent with the development of green environmental requirements.This paper mainly studies the technology of silane film preparation under different process conditions,to know the optimum process conditions.Besides,the silane film is modified by zinc-nickel particles.The electrochemical deposition technique is effectively combined to improve the thickness and unevenness of the film.Afterwards,electrophoretic coating modified by silane to establish a metal matrix/silane film/electrophoretic coating corrosion protection system for carbon steel and other materials.The main results are as follows:（1）The optimal hydrolysis conditions of KH560 silane solution is p H=4.5,hydrolysis time is 48h.The optimal hydrolysis conditions of KH550 silane solution is p H=8.0,hydrolysis time is 8h.The optimal ratio in both silane hydrolysis is V_silane:V_{Et OH}:V_H2O=5:75:25,the film forming time is 3min,and at 100℃curing 1h.Under the conditions,the corrosion potential of KH-560 silane film is-0.492V,and KH-550silane film is-0.532V.The corrosion current density of both silane films is close to10^-6A/cm².（2）The films modified by Zr（SO₄）₂,Zn（NO₃）₂ and Si O₂,show improvement of corrosion resistance in different degrees.The zinc-nickel particle doping experimental results show that:when the concentration of zinc-nickel solution in the sulfate system is about 15%,the properties of the silane composite film are the best,and the corrosion current density is 10^-6A/cm².The concentration of zinc-nickel solution in the zincate system is about 20%,the corrosion current density is 10^-7A/cm².In addition,both impedance values of the silane composite film modified with zinc-nickel particles are 10⁵Ω.（3）The test results of the electrophoretic coating doped with silane show that:the resistance of the electrophoretic coating increases with the increasing concentration of silane in the electrophoretic solution.The largest impedance value is 10⁷Ωwhen silane in the electrophoretic solution exceeds a certain value,this process will fail.Therefore,the choice of appropriate silane concentration is the premise of preparation of excellent electrophoretic coating.（4）The results of infrared spectroscopy showed that the cross-linked product[-Si-O-Si-]_n and the strong chemically bonded Si-O-M were produced after the hydrolysis and condensation reaction of the silane.And the Si-O-Si absorption peak near the 1010cm^-1 has different degree of broadening,indicating that silane has a good chemical bonding on the metal surface.Scanning electron microscopy revealed that the modified silane film effectively improved the cracks and holes.In addition,the modified silane film also has dense structure and excellent uniformity.（5）Based on the original research contents,KH-570,KH-792 and JSC-1120 were selected to repeat the experiment on 3003 aluminum alloy and AZ91D magnesium alloy substrate to verify the universality of the experimental study,and the results are very satisfactory.Therefore,the research ideas and methods of this experiment is feasible.