| 摘要 |
PURPOSE:To enhance the corrosion resistance of a steel sheet, by coating an aq. acidic soln. contg. the water-soluble chromium compd. consisting essentially of trivalent chromium, an inorg. colloidal compd., and an inorg. anion on the steel surface, and then drying the soln. CONSTITUTION:The aq. acidic soln. contg. the water-soluble chromium compd. consisting essentially of trivalent chromium, an inorg. colloidal compd., and an inorg. anion is prepared. The aq. acidic soln. is coated on the metal surface, and then dried to obtain a chromate film having excellent corrosion resistance. As an alternative method, a >=2-valent metal ion is incorporated into the above- mentioned aq. acidic soln., and the obtained aq. acidic soln. can be used. Silica sol is preferably used as the inorg. colloid, and the ions of phosphoric acid and condensed phosphoric acid are preferably used as the anions. The ions of Mg, Ca, Sr, Ba, Al, Zn, Cu, Bi, etc., are exemplified as the metal ions.
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