| 摘要 |
The invention relates to a chromium-free, corrosion prevention treatment for steel, zinc or zinc alloys, aluminum, magnesium or alloys thereof in which the metal surfaces are contacted in a first step with a first aqueous solution having a pH of 1.5 to 5 which contains Ti and/or Zr and/or Si ions and at least such a quantity of fluoride that the atomic ratio of Ti to F and/or Zr to F and/or Si to F is in the range from 1:1 to 1:6 and then, optionally after rinsing with water, and thereafter in a second step are contacted with a second aqueous solution having a pH of 1.5 to 5 which contains Ti and/or Zr and/or Si ions and at least such a quantity of fluoride that the atomic ratio of Ti to F and/or Zr to F and/or Si to F is in the range from 1:1 to 1:6, and which additionally contains such a quantity of soluble anions of oxo acids of Mo (VI) and/or W (VI) that the total concentration of molybdenum and/or tungsten is in the range from 5 to 1500 mg/l.
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