| Hot dip galvanizing is one of the most economical and effective means to improve the corrosion resistance of steel materials.However,Galvanized steel is easy to produce white rust during storage and transportation in damp conditions,affecting the appearance,and even reducing the service life of galvanized steel.In order to solve the problem of the corrosion of zinc on galvanized steel surface,the traditional treatment method is to use chromate passivation.However,chromate has been phased out due to its highly toxic,carcinogenic and harmful to the environment.Silane coupling agent treatment on metal surface is an ideal substitute for chromate passivation due to its advantages of non-toxicity,non-pollution,and high adhesion.However,the corrosion resistance of silane coating has limited and does not have well long-term protection performance on the metal surface resulted from its thin thickness,micro-pores and micro-cracks.Graphene oxide(GO)has received extensive attention due to its large specific surface area,excellent barrier performance and its surface containing a large number of modifiable functional groups.However,when the GO film is directly formed on the metal surface,the weak adhesion between the film layer and the metal and the vulnerability to holes limit its application.Therefore,we want to prepare a coating with high corrosion resistance on the surface of zinc by combining the advantages of GO and silane.The strong adhesion of silane can enhance the adhesion between GO and metal matrix,and the strong barrier performance of GO can improve the barrier performance of silane coating.Herein,we preparing a GO doped modified silane composite films with a certain thickness and high corrosion resistance on the surface of zinc.In this dissertation,a reduced graphene oxide(rGO)coating was prepared on the surface of zinc by immersing in GO aqueous dispersion.A reduced graphene oxide/?-(2,3-glycidoxypropyl)propyltrimethoxysilane(GPTMS/rGO)composite coating was prepared on the surface of zinc by immersing zinc plate in a graphene oxide(GO)and GPTMS mixed aqueous dispersion.The formation mechanism of the coating was investigated by means of scanning electron microscopy(SEM),Raman spectroscopy(Raman),Fourier transform infrared absorption spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS).The corrosion resistance properties and anticorrosion mechanism of the coating were studied by electrochemical impedance spectroscopy(EIS)and Tafel polarization curves.The following main results are obtained:The GO was reduced and some oxygen-containing functional groups were reduced in the process of rGO coating formation on the surface of zinc.The structure of rGO coating is loose and porous.With the increase of coating formation time,the rGO coating becomes thicker,and cracks appear on the surface and increase continuously.The EIS results showed that the rGO coating did not have a good protective effect on the zinc substrate,and the impedance value decreased compared with the untreated zinc.As the film thickened,the impedance value decreased.The GO was reduced in the process of GPTMS/rGO coating formation on the surface of zinc,and a dense network structure was formed by chemical bonding between GPTMS and GO and between GPTMS and metal.With the increase of film formation time,the thickness of the GPTMS/rGO composite film increased continuously and can reach more than 20 ?m.The coating was densest at forming 6h,and after 6h,holes appeared in the coating and increased continuously.EIS and Tafel polarization results show that the GPTMS/rGO composite coating with high corrosion resistance and good resistance to immersion,the impedance value reached 2.21M?·cm2,polarization.The resistance Rp of GPTMS/rGO coating reached 1.34 M?·cm2,increased 1000 times compared to the pure zinc,200 times higher than GPTMS coating,and the self-corrosion current density icorr decreased to 0.029 ?A·cm-2,two orders of magnitude smaller than pure zinc and GPTMS. |
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