Modification of Nano-SiO_2 and Its Effect on the Properties of Waterborne Polyurethane Resin Coating

In aqueous ethanol solution,the surface of nano-SiO2 was modified by silane coupling agent KH560.And the particle sizes were measured.The effects of nano-SiO2 content,alcohol percentages and the modification agents on dispersity were discussed.The chromium-free passivation solution was made from the modified nano-SiO2 dispersions,water polyurethane resin and inorganic constituent compound,and it may be coated on the hot galvanized sheet.Corrosion resistances of nano-SiO2 modified polyurethane composite passivation film and unmodified polyurethane composite passivation film were characterized by the electrochemical Tafel polarization curves,AC impedances(EIS) and the neutral salt spray tests.The results may show that compared with the latter the former corrosion resistance have been greatly improved.