| As a kind of metal anticorrosive coating with excellent properties,zinc-aluminum coating(Zn/Al coating)is widely used in all walks of life.Traditional Zn/Al coating as chromate film skeleton,although the preparation of zinc chromate aluminum coating has excellent corrosion resistance,Cr6+is toxic carcinogenic,which is harmful to the environment and human body,so the preparation of a kind of green environmental protection,and excellent corrosion resistance and good mechanical properties of Zn/Al coating is a kind of development trend.In this paper,based on the traditional Zn/Al coating research,starting from the basic components,the single factor experiment method was used to determine the basic components of the Zn/Al coating without chromium.Through the orthogonal experiment of 5 factors and 4levels,the adhesion,appearance and corrosion resistance of the coating were used as evaluation indexes to determine the optimal formula of the Zn/Al coating without chromium coating was improved by the addition of nanometer reinforcing materials.The optimal formula of coating solution is:30%zinc-aluminum powder,ratio of zinc-aluminum to 6:1,6%binder,20%wetting agent,2%thickener,2 to 3 drops defoamer,and the remaining amount is distilled water.Based on the optimized formulation,Zn/Al coating was prepared,and the appearance,hardness and corrosion resistance of the coating were evaluated.The coating is made of sheet zinc powder and aluminum powder stacked on top of each other,with a coating thickness of about 21mm and a good adhesion to the substrate.In 3.5% NaCl solution,the corrosion potential and corrosion current of the Zn/Al coating were-0.86V and1.1556×10-5A×cm-2,respectively.In order to further improve the corrosion resistance and hardness of Zn/Al coating,nano-reinforced materials such as nano-particle zirconia(ZrO2),nano-graphene oxide(GO)and ZrO2+GO mixture were added to Zn/Al coating,and corresponding nano-composite coating was prepared.The corrosion resistance of different coatings was analyzed by electrochemical experiments.The results showed that the corrosion potentials of pure Zn/Al coating,Zn/Al+ZrO2 composite coating,Zn/Al+GO composite coating and Zn/Al+ZrO2+GO composite coating were-1.049V,-0.965V,-0.895V and-0.849V respectively,and the corrosion current densities were 6.183×10-5A×cm-2,4.063×10-5A×cm-2,1.784×10-5A×cm-2and1.104×10-5A×cm-2,respectively.The addition of nano-reinforced materials has a significant effect on the improvement of corrosion resistance of Zn/Al coating.The microhardness test showed that the hardness of pure Zn/Al coating,Zn/Al+ZrO2 composite coating,Zn/Al+GO composite coating and Zn/Al+ZrO2+GO composite coating were 118.37HV,135.86HV,141.52HV and 159.14HV,respectively.The addition of nano-reinforcing particles improved the hardness of chromium-free Zn/Al coating. |
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