Function of Nanoscale Silica in the Process of Trivalent Chromium Passivation for Galvanizing Coating

Nanoscale SiO_2 was introduced into trivalent Cr passivation solution to conduct room temperature coloring passivation-simultaneous sealing of galvanizing coating.The corrosion resistance of resultant passivation coating was evaluated by conducting neutral salt-spray test and measuring electrochemical polarization curve.It was found that the trivalent Cr passivation solution containing 3.5 g/L nanoscale SiO_2,had good stability.Nanoscale SiO_2 was co-deposited with trivalent Cr and had synergistic effect with the latter,resulting in significantly improved brightness of the passivation coating and greatly increased corrosion resistance of the galvanizing coating.