Electrochemical Behavior of Organic Film with Nano-silica on Galvanized Sheet

Organic-inorganic composite coatings on hot-dip galvanized steel sheet were prepared by adding different contents of nano-SiO2 into acrylic resin emulsion. The electrochemical behaviors of nano-SiO2 modified acrylic resin film in 5% NaCl solution were studied by electrochemical measurement techniques. The results indicated when there were 8%～12% SiO2 in organic film, the anodic polarization curves showed an analogous passivation property and increased the anodic polarization action of the galvanized coat, prohibited the electrode reaction better. The reason is might result from the chemicaal reaction of SiO2 in organic film with Zn and production of zinc silicate compound, with stable performance; or result from dissolution-redeposition of sol SiO2 in the film.