| 摘要 |
PURPOSE:To form a chromate film with superior corrosion resistance and superior suitability to coating on each surface of a galvanized steel sheet by chromating the steel sheet with an aqueous chromating soln. having a specified composition contg. chromic anhydride, fluorine ions or fluorine complex ions, and silicic acid sol. CONSTITUTION:A chromating soln. contg. 5-50g/l chromic anhydride, 0.1-10g/l fluorine ions or fluorine complex ions, and 2-200g/l (expressed in terms of SiO2) silicic acid sol is prepd. Hydrofluoric acid, ammonium fluoride, sodium hexafluoroaluminate or the like is used as an additive for feeding fluorine ions or fluorine complex ions. A chromate film is formed on each surface of a galvanized steel sheet by chromating the steel sheet with the chromating soln. |
