Atotech Deutschland Gmbh

Jaroslava Krizova

Björn Dingwerth

Vaclav Kriz

Jiri Kloubek

The invention relates to a treatment solution for producing substantially chromium(VI) free black conversion layers on alloy layers containing zinc, the solution comprising the following: (i) at least one first carboxylic acid having 1 to 8 carbon atoms, the acid containing no polar groups with exception of the carboxyl group and being a monocarboxylic acid, (ii) at least one second carboxylic acid having 1 to 8 carbon atoms, comprising at least one further polar group that is selected from &#x2014;OH, &#x2014;SOH, &#x2014;NH, &#x2014;NHR, &#x2014;NR, &#x2014;NR, and &#x2014;COOH (wherein R is a C-Calkyl group), (iii) 20 to 400 mmol/l Crand (iv) 50 to 2000 mmol/l NO. The invention further provides a method for the black passivation of surfaces containing zinc, wherein the surface to be treated is immersed into such a treatment solution.

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Lucany n.N., Czechia

Jaroslava Krizova