| 摘要 |
A phosphating process employs an acidic phosphating solution containing metal ions, oxo acid ions and phosphoric acid ions to which alkali is added for in situ generation of oxidising agent including nitrite ions by the oxo acid, the solution having a temperature of max. 40 deg.C, a PH of 2.5-4.5 and a redox potential of 150-550 mV. The process is useful in the zinc phosphating of steel. Phosphating can be carried out at ambient temperature under automatic control, without direct addition of oxidising agent to the bath. The bath is stable, phosphating reaction occurs only at the steel surface, and H2 gas and sludge formation are reduced.
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