| 摘要 |
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-OH,-SOH,-NH,-NHR,-NR,-NR, and-COOH (wherein R is a C-C-alkyl group), (iii) 20 to 400 mmol/l Crand (iv) 50 to 2000 mmol/l NO, and wherein (a) the total concentration of carboxyl groups of the first carboxylic acid(s) is within a range of 5 to 150 mmol/l, (b) the total concentration of carboxyl groups of the second carboxylic acid(s) is within a range of 5 to 150 mmol/l, (c) the ratio of the concentration (in mol/l) of NOto u Cris >= 1, and (d) the following prerequisite is met (formula (I)), wherein(C1) is the total concentration (in mol/l) of carboxyl groups of the first carboxylic acid(s),(C2) is the total concentration (in mol/l) of carboxyl groups of the second carboxylic acid(s),(Cr) is the concentration (in mol/l) of Cr, and(NO) is the concentration (in mol/l) of 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. |
