| 摘要 |
The Cr concentration is made to 0.01-1 mol./l by mixing one, or two above species among Na2CrO4, Na2Cr2O7, K2CrO4, K2Cr2O7, or CrO3 and the PO4-3 concentration is made to 0.4-0.75 mol/l by mixing one, or two above species among H3PO4, NaH2PO4, Na2HPO4, (NH4)H2PO4, or (NH4) 2HPO4. The Cr3+ concentration ratio to the total Cr is made to 0.1- 0.5 by adding reducing agent, so the chromate solution is made by adding water soluble Cu compound for the Cu2+ concentration to be 0.004-0.012 mol/l. Chromate treated steel plate with good corrosion resistance and good surface figure can be manufactured by using this chromate solution.
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