Alloying Elements On The Mechanical Zinc Coating Corrosion Resistance

Mechanical Plating is a kind of way with no crystallization of anticorrosion technology formed metal coatings. In recent years, along with the technological progress and the development of the society, mechanical plating technology develops rapidly in surface treatment field. At present for mechanical galvanizing research mainly focuses on technology research and coating in the form of zinc layer mechanism. The corrosion resistance performance of coatings for the study was just in single alloy element influence on the coating, while the study about the effect of different alloy elements on mechanical galvanized layer corrosion resistant performance is very rare. Therefore this paper researches RE,Al,Sn alloy elements on mechanical galvanized layer to the influence of the corrosion resistance and erosion mechanism.This paper reviews mechanical galvanizing process, mechanical galvanizing layer's type and mechanical galvanizing in the developing situation of domestic and foreign. Adopt mechanical galvanized little tin salt deposits fabrication processes to prepare the optimized Zn, Zn-2%RE, Zn-3%Al, Zn-3%Al-1%RE, Zn-25%Sn coating. And then with neutral salt spray corrosion test, immersion, polarization curve technique, AC impedance technology, electronic scanning microscope and XRD methods. Comparative studies five kinds of coating in the environment of 5% NaCl solution corrosion resistant performance. According to the test results, analyse RE, Al, Sn alloy elements on mechanical galvanized layer at 5% NaCl solution influence of corrosion resistance and reason, discussing on mechanical galvanized coating corrosion behavior in the environment.Through analyzing the phenomenon and the relevant data, which can reach the following conclusion:At 5% NaCl solution adding RE, Al and Sn alloying element of zinc corrosion layer's corrosion resistant performance was obviously superior than the corrosion resistant performance of Zn coating. Namely, add alloy elements coating corrosion resistant performance than the Zn coating; The corrosion resistance rule is:Zn-25%Sn> Zn-3%Al-1%RE> Zn-2%RE> Zn-3%Al> Zn. This shows that addition of suitable amount of alloying elements can obviously improve corrosion resisting property of the coating.Alloy elements improve coating corrosion resistant performance reasons for:Rare earth can improve the plating metal micropowder adsorption sedimentary way, enhance the oxide film adhesion and self-healing capability, absorb coating formed produced hydrogen, and play the role of purification coating, thus reducing coating the defects to improve corrosion resistance. Adding appropriate amount of Al element in galvanized layer makes its surface produces densityβ-Al2O3·3H2O passivating film in corrosion process, leading to increasing reaction resistance and delaying the process of the corrosion. Furthermore, aluminum has the self-healing capability. Meanwhile the reaction between Al and Zn can produce amorphous zinc and aluminum compounds that is "the shield", which is further protective coating effect and impoves corrosion resisting property of the coating. Sn in coating effect, makes a adhesive coating have greater densify; In a neutral aqueous solution Sn is very stable, corrosion SnO2 generated extremely stable. Because of the standard Sn potential isφ°Sn2+/Sn=-0.136V, and according to the cathode element enrichment doctrine, adding an appropriate amount of Sn can make coating surface oxidation film maintain stability.