Forming corrosion-protection layers on surfaces made of zinc, aluminum or magnesium and alloys of metals, comprises contacting surface of metals/metal alloys with solutions comprising chromium (III) ions, metal ions and complexing agent

摘要

The method for forming corrosion-protection layers on surfaces made of zinc, aluminum or magnesium and alloys of the metals, comprises contacting the surface of metals/metal alloys with first solution comprising chromium (III) ions, metal ions from the surface metal/surface metal alloy and a complexing agent where first treatment solution has pH-value of 1.0-4.0, and then contacting the surface of the metal with second solution comprising chromium (III) ions, metal ions from the surface metal/surface metal alloy and a complexing agent where second treatment solution has pH-value of 3.0-12.0. The method for forming corrosion-protection layers on surfaces made of zinc, aluminum or magnesium and alloys of the metals, comprises contacting the surface of the metals or metal alloys with a first solution comprising chromium (III) ions, metal ions from the surface metal or surface metal alloy and a complexing agent where the first treatment solution has a pH-value of 1.0-4.0, and then contacting the surface of the metal with a second solution comprising chromium (III) ions, metal ions from the surface metal or surface metal alloy and a complexing agent where the second treatment solution has a pH-value of 3.0-12.0. Both treatment solutions contain 0.5-200 g/l of the complexing agent, 0.001-10 g/l of fluoride ions, and 0.1-10 g/l of chloride ions, where 0.5-10 g/l of soluble chromium (III) ions are added to s both treatment solutions. The treatment solution according to the first contacting step has a temperature of 10-50[deg] C. The treatment solution according to the second contacting step has a temperature of 10-80[deg] C. The treatment duration in the treatment solution in both steps is 10-600 seconds. The substrate to be treated is directly dried after contacting with the both treatment solutions without final rinsing step. A passivation treatment is supported in the first contacting step by cathodically switching the substrate in a passivation solution, where the cathodic flow density on the substrate is 0.05-10 A/dm 2.