| 摘要 |
PURPOSE:To dispense with the pretreatment and aftertreatment such as pickling, washing with water, etc., and to simplify the bath control by treating an alloyed galvanized steel sheet in two steps by using two kinds of treating liqs. wherein the weight ratio of a florine complex salt to CrO3 and the concns. are specified. CONSTITUTION:The weight ratio of >=1 kinds of fluorine complex salt selected from Na3AlF6, Na2SiF6, (NH4)2SiF6, and K3AlF6 to CrO3 is regulated to 1/10-1/2, the concn. of the fluorine complex salt is regulated to 1-20g/l, and the concn. of CrO3 is regulated to 10-40g/l in an aq. soln. to be prepared. An alloyed galvanized steel sheet is dipped into the first treating liq. Then the sheet is dipped in the second treating liq. wherein the weight ratio of the fluorine complex salt to CrO3 and the concn. of CrO3 are respectively regulated to a value equal to or more than the corresponding value of the first treating liq. The sheet is pulled out of the treating liq., and dried in that condition. Namely, high-speed treatment is made possible by the first treating liq., a plural- layered film is formed by the second treating liq., and the quality of the chromate film is improved. |
