| 摘要 |
PURPOSE: A trivalent chromate solution is provided in which hexavalent chrome and oxidizer are not contained, a method for preparing the solution is provided, and a method for preparing a film of the solution by coating the solution on electro-galvanized automobile parts and hot dip galvanized strip and steel pipe is provided. CONSTITUTION: In a chromate solution that is a passivation agent in which hexavalent chrome and oxidizer are not contained, but trivalent chrome is contained, the chromate solution is characterized in that it contains sulfate and sulfite, wherein the sulfite is sodium sulfite or potassium sulfite, and wherein the chromate solution contains 0.5 to 15 g/L of sulfite. The method for preparing a chromate solution comprises the processes of dry bathing a base compound solution to 3 to 12 vol.% of water; adding 3 to 10 vol.% of subsidiary compound solution to the dry bathed base compound solution; and adding nitric acid to the mixture so that pH of the chromate solution becomes 1.5 to 2.0, wherein the base compound solution comprises one or more selected from the group consisting of 25 to 35 g/L of trivalent chrome and 0.5 to 15 g/L of sulfate and sulfite; one or more selected from the group consisting of 1 to 3 g/L of nitrate and 0.1 to 15 g/L of Co, Mo, Ti and Ni; and one or more selected from the group consisting of 0.1 to 1 g/L of PEG, PVA and formalin condensate of sodium naphthalene sulfonate on the basis of the chromate solution, and the subsidiary compound solution comprises 50 to 350 g/L of phosphoric acid; methanol or methylene chloride, or methanol and methylene chloride; and one or more selected from the group consisting of silica sol, formic acid, meta acrylic acid and acryl amide.
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