CHROMATE SOLUTION FOR AUTOMOBILE FUEL TANK HAVING SUPERIOR CORROSION RESISTANCE AND FUEL RESISTANCE AFTER PROCESSING AND METHOD FOR MANUFACTURING CHROMATE TREATED HOT DIPPED GALVANIZED IRON USING THE SAME

摘要

PURPOSE: A chromate solution and a method for manufacturing chromate treated hot dipped galvanized iron using the same are provided to improve corrosion resistance and fuel resistance properties after processing by applying a hardening solution of glycidyl based silane so that chromate solution is adequately reacted with a plating steel sheet material, thereby strengthening rigidity of the film material when deep drawing. CONSTITUTION: In a chromate solution for an automobile fuel tank comprising a chromium aqueous solution in which a constituent ratio of trivalent chromium in 7 to 50 g/l of chromium constituents is 0.4 to 0.8, a main solvent solution containing 50 to 80 weight parts of phosphoric acid, 20 to 40 weight parts of fluoric acid, 300 to 2000 weight parts of colloidal silica, and 5 to 15 weight parts of sulfuric acid for the chromium aqueous solution, and a hardening solution of 20 to 60 weight parts for the main solvent, wherein the hardening solution is adjusted to 2 to 3 of pH, and wherein the hardening solution comprises 2 to 10 weight parts of a glycidyl silane aqueous solution. In a method for manufacturing a chromate treated steel sheet by coating a chromate solution on a plating steel sheet, the method comprises the step of baking the chromate solution coated on the plating steel sheet at a steel sheet temperature of 140 to 250 deg.C after coating a chromate solution on a plating steel sheet material in a dry film adhesion amount of 30 to 150 mg/m2.