Study Of Chromium-free Composite Passivation Solution Based On Acrylic Emulsion

In this paper, the organosilicon modified acrylic emulsion synthesized by soap-free emulsion polymerization and ?-(2,3-epoxypropoxy)propytrimethoxysilane were used as the film-forming material and polypyrrole was used as corrosion inhibitor. Chromium-free composite passivation solution for galvanized steel sheet was prepared by solution blending through orthogonal experimental design. Also,another chromium-free composite passivation solution for galvanized steel sheet was prepared via solution mixing by using the commercial acrylic emulsion and KH560 as film-forming material, polypyrrole and phytic acid as corrosion inhibitor and ammonium hydroxide as pH regulator through orthogonal experimental design.The effects of organic silicon functional monomer and methyl glycidyl ester of acrylic(GMA) dose on the emulsin polymerization were studied. The size and size distribution of latex particles were characterized by nanoparticle size analyzer. The optimal conditions of the preparation of organic silicone modified acrylic emulsion is that organic silicon functional monomer and GMA monomer were 25% weight parts and 3% weight parts of the acrylate monomer, respectively.The optimal formula of chromium-free composite passivation solution based on organic silicone modified acrylic emulsion determined through the orthogonal experiment test contained 12% of organic silicone modified acrylic emulsion, 8% of the KH560 hydrolysate and 0.02% of the polypyrrole. The optimal passivation process is that the curing temperature was 120? and the curing time was 5 min. The optimal formula of chromium-free composite passivation solution based on commercial acrylic emulsion determined through the orthogonal experiment test contained 14% of the commercial acrylic emulsion, 1% of the KH560 hydrolysate,0.03% of the polypyrrole, 1% phytic acid and the passivation solution pH value is4.00. The optimal passivation process is that the curing temperature was 140? and the curing time was 5 min.The morphology and elements of the passivation film were analyzed by scanning electron microscopy(SEM) and EDX spectroscopy. The corrosion resistance of the composite film was characterized by AC impedance, tafel test and salt spray test. The results show that the film with compact structure is mainly composed of C and Si elements and exhibit good humidity resistant, adhesion and corrosion resistance.