| Water-born zinc aluminum alloy coating is developed on the technology of Dacromet coating. Corrosion resistance is not good as the Dacromet, the price is expensive, which limits its wide application in our country. This paper aimed at the key technical problems of non chromatedacromet, using the water-based acrylic resin and silane passivating agent as binder instead of chromic anhydride to prepare a new type of non chromium zinc- aluminum alloy coating and systematically analyzed the corrosion resistance and corrosion resistance mechanism of Cr free Zn-Al based coatings.Firstly, the effect of the ratio of water based acrylic resin and silane on the comprehensive properties of the coating was discussed. Based on the five factors of metal powder, binder, wetting agent, dispersing agent and corrosion inhibitor, L16(45) orthogonal experiment was designed, and the best formula of coating was obtained by using the combined force, appearance and corrosion resistance of the coating.Secondly, the comprehensive performance of the coating was studied in the paper. Firstly, the viscosity, fineness and pH value of the optimized coating were tested, and the thickness, hardness and surface morphology of the coating were tested. The corrosion resistance, neutral salt spray test and electrochemical corrosion performance were analyzed. The transition process of the corrosion products was obtained from the intact coating and the coating with the immersion time. The corrosion resistance of the coating was tested.Finally, the corrosion resistance mechanism of optimized coating was studied by electrochemical impedance spectroscopy and the transformation mechanism of zinc aluminum alloy coating in NaCl solution.In this paper, XRD, SEM, EDS and EIS were used as the main means to characterize the morphology and composition of the coating. The optimized coating had excellent corrosion resistance. |
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