| The traditional surface passivation process of galvanized plate mainly employs hexavalent chromium passivating treatment. However, hexavalent chromium is deadly poisonous and seriously harmful to human body and environment, thereby products containing hexavalent chromium are restricted strictly. In addition, with the increase of the requirement for coating in galvanized plate processing technology, the requirements for heat resistance, water resistance, self-lubrication and corrosion resistance become more and more stringent. Therefore, the development of chromium-free self-lubricating passivation technology to solve the pollution problem caused by hexavalent chromium is an inevitable trend of green industry technology.1) Through response surface curve method, the optimum formula of chromium-free self-lubricating passivating liquid was screened:3.88% of composite silane coupling agent,1.55% of ammonium molybdate,3.53% of nano silica sol, 3.15% of tannic acid,3.4% of water emulsion solid and 0.15% of polyethylene wax. Finally, the self-lubricating fluid with 15%?16% of solid portion,6.5?7 mPa·S of viscosity,1.01?1.2%kg/dm3 of density and of 6.5 of pH value was obtained.2) Through advanced pressure roll coating technology, uniform and transparent chromium-free self-lubricating film was prepared, and the industrial production standard curve of the amount of self-lubricating film was established; scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), glow discharge optical emission spectrometry (GD-OES) and infrared spectroscopy (IR) were applied to analyze the micro characteristics of film; With electrochemical test and salt spray test, the corrosion resistance of film was investigated comparatively to analyze the surface properties such as fingerprint resistance, water resistance and heat resistance, the experiments proved that the performance of the self-lubricating layer is excellent.3) The formation mechanism of chromium-free self-lubricating film was studied:(i) Silane molecules form a compact three-dimensional network structure on the surface of galvanized plate to wrap the inorganic inhibitor; (ii) The zinc molybdate generated by the reaction of zinc and ammonium molybdate is filled in the reticular silane film; (iii) Aqueous styrene acrylic emulsion and polyethylene wax form uniform and stable self-lubricating film on silane film; And the corrosion resistance mechanism of chromium-free self-lubricating passivation film was analyzed:firstly, aqueous styrene acrylic emulsion forms homogeneous film to resist the corrosive medium diffusing to base metal; secondly, compounds generated by ammonium molybdate and tannic acid separately improve the electric resistance of self-lubricating film simultaneously, thereby inhibiting corrosion reaction, reducing reaction rate, so as to alleviating corrosion finally.4) Numerical modeling and finite element simulation concerning the punching process of chromium-free self-lubricating passivation galvanized plate were carried out. The results showed that, the production of passivation galvanized plate should mainly apply rolling method to avoid the use of stamping/extrusion with large load; Optimum operation parameters of the self-lubricating passive film were obtained: 0.48 of filler ratio,900 mg/m2 of film thickness,150? of temperature and 150N of load; It is obvious that the stamping property of passivation galvanized plate with self-lubricating performance is significantly better than other products.Chromium-free passivation film has been applied and spread in industry, this research was subsidized through 863 Program decreed by Ministry of Science and Technology, and the obtained research results have an important reference value for the research and development of self-lubricating passive film. |
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