Conversion layers for surfaces containing zinc
OwnerBjörn Dingwerth, Andreas Noackinventors
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Abstract
The invention relates to a process for producing a coating layer which protects against corrosion, in which a surface to be treated is brought into contact with an aqueous treatment solution containing at least one source of chromium(III) ions and also at least one organic compound which oxidizes zinc in weakly acidic or acidic solution. Here, the decorative and functional properties of the surface are retained or improved. In addition, the known problems associated with the use of chromium(VI)-containing compounds are avoided.
Claims21
A process for producing essentially chromium(VI)-free conversion layers on zinc or zinc alloy layers, comprising
- immersing a surface comprising a zinc or zinc alloy layer in an aqueous treatment solution containing Cr3+ ions and further comprising at least one organic compound selected from:
- where R1 to R5 are each, independently of one another,
- a) a hydrogen atom or an alkyl group which has from 1 to 10 carbon atoms and may be linear or branched or
- b) an —NR2, —NO2, —COOR, —OR, —SO3R group where R═—H or an alkyl group which has from 1 to 5 carbon atoms and may be linear or branched,
- with the proviso that from 0 to 2 radicals R1 to R5 are selected from group b).
A process for the treatment of a zinc or zinc alloy surface,
- characterized in that the surface to be treated is dipped into a treatment solution comprising
- at least one source of Cr3+ ions and
- at least one organic compound selected from the group consisting of
- where R1 to R5 are each, independently of one another,
- a) a hydrogen atom or an alkyl group which has from 1 to 10 carbon atoms and may be linear or branched or
- b) an —NR2, —NO2, —COOR, —OR, —SO3R group where R═—H or an alkyl group which has from 1 to 5 carbon atoms and may be linear or branched,
- with the proviso that from 0 to 2 radicals R1 to R5 are selected from group b).
Dependencies are inferred from the claim text.