| 摘要 |
PROBLEM TO BE SOLVED: To provide a chemical processing method for forming a trivalent chromium chemically processed coating film having excellent heat corrosion-resistance similar to the initial make-up of an electrolytic bath even when metal ions of Zn and Fe or the like are dissolved in a trivalent chromium chemically processing liquid in a step of forming the trivalent chromium chemically processed coating film on zinc or zinc-alloy plating. SOLUTION: In the chemical processing method for forming the trivalent chromium chemically processed coating film on zinc or zinc alloy plating, a chelate agent is added to the trivalent chromium chemical processing liquid in a range of 0.1-1.0 mol to the total increase of 1 mol of zinc and iron ions dissolved in the trivalent chromium chemical processing liquid during the step of forming the trivalent chromium chemically processed coating film on zinc or zinc alloy plating by using hexavalent chromium-free trivalent chromium chemical processing liquid containing the chelate agent of 0.5-1.5 mol to trivalent chromium ions of 1 mol. COPYRIGHT: (C)2009,JPO&INPIT
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