| 摘要 |
<p>Metal surfaces, particularly the zinciferous surfaces of zinc-coated steel, can be given a chromate conversion coating that is superior in terms of blackening resistance and white rust resistance by drying into place on the surfaces a layer of a treatment liquid that contains water, hexavalent chromium atoms, trivalent chromium cations, nitrate ions and one or more types of metal ions selected from the group consisting of Ni, Co, Zn and Al, the molar ratio of the total of these metal ions to nitrate ions being in the range from 0.05 to 1.0, the molar ratio of trivalent chromium ions to hexavalent chromium atoms being in the range of 0.11:1.0 to 1.0:1.0, and the molar ratio of nitrate ions to total chromium atoms being in the range of 2.1 to 5.5. Preferably, the coating formed has a chromium content of 10 to 100 mg/m2.</p> |
