| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a surface-treated steel sheet, by which a Zr oxygen compound film can be continuously and stably formed on a steel sheet.SOLUTION: The method for manufacturing a surface-treated steel sheet comprises immersing a steel sheet 1 in an electrolytic treatment solution 31 containing Zr ions and F ions to continuously carry out an electrolytic treatment to form a film essentially comprising a Zr oxygen compound with a Zr amount in the film of 30 mg/mor more on the steel sheet. The electrolytic treatment solution 31 has a Zr ion concentration of 3,000 to 10,000 ppm by weight and a pH of 2 to 4. A first replenishment solution and a second replenishing solution described below are each continuously supplied to the electrolytic treatment solution 31. The first replenishment solution contains a zirconium fluoride compound with a Zr ion concentration in the range from 10,000 to 250,000 ppm by weight and has a pH of 5 or less; and the second replenishment solution contains a zirconium compound containing no fluorine, with a Zr ion concentration in the range from 10,000 to 200,000 ppm by weight and has a pH of 5 or less.SELECTED DRAWING: Figure 1 |
