| 摘要 |
PURPOSE:To easily and stably obtain a coated product having superior corrosion resistance by forming a film on a metal with a chemical treating soln. contg. Zn ions and phosphate ions and by treating the film with an acidic aq. phosphoric acid soln. to form a base film for improving the corrosion resistance of a coated product. CONSTITUTION:A steel sheet cleaned by degreasing and washing is dipped in a chemical treating soln. contg. Zn ions and phosphate ions to form a film. The steel sheet is then washed and sprayed with an acidic aq. phosphoric acid soln. prepd. by adding phosphoric acid to Zn ions, Mn ions, etc., and carrying out dissolution and dilution with water. By the spraying, zinc phosphate in the upper layer part of the film is dissolved and removed to form a base film for improving the corrosion resistance of a coated product. After the steel sheet is washed, cationic electrodeposition paint is electrodeposited, washed and cross-linked by heating to obtain a coated product. The pH of the acidic aq. phosphoric acid soln. is desirably made lower than or nearly equal to the pH of the chemical treating soln. |
