Abstract: The present invention relates to a process for corrosion protection of an iron-containing substrate wherein a first zinc-nickel alloy layer, a second zinc-nickel alloy layer and a black passivate layer are deposited onto the substrate. The nickel concentration in the second zinc-nickel alloy layer is higher than the nickel concentration in the first zinc-nickel alloy layer. The substrate surface obtained is homogenously black with an appealing decorative appearance and both resistance against white rust and red rust are improved.

Abstract: Additives for electrolyte baths for the electrodeposition of zinc or zinc alloy layer are described. The additives are polymers with terminal amino groups. These polymers are obtainable by reaction of at least one diamino compound (having two tertiary amino groups) with at least one di(pseudo)halogen compound, wherein the diamino compound is used in stoichiometric excess. The additives effect, in particular, a very little formation of bubbles and only few burnings as well as a uniform distribution of layer thickness in the electrodeposition of zinc or zinc alloy layers.

Abstract: The present invention is related to an apparatus and a method for the electrolytic deposition of a zinc or zinc alloy layer on a workpiece, the apparatus comprising a container to hold the metal plating bath divided into at least two compartments with an electrode assembly in the container, the assembly comprises in a first compartment a soluble anode to provide ions of the at least one metal to be deposited and a cathode corresponding to the workpiece to be metal plated and in an anolyte compartment separated from the first compartment by an ion exchange membrane comprises an insoluble anode and wherein the electrode assembly in the compartments are connected by an adjustable power supply.

Abstract: The present invention relates to a process for corrosion protection of an iron-containing substrate wherein a first zinc-nickel alloy layer, a second zinc-nickel alloy layer and a black passivate layer are deposited onto the substrate. The nickel concentration in the second zinc-nickel alloy layer is higher than the nickel concentration in the first zinc-nickel alloy layer. The substrate surface obtained is homogenously black with an appealing decorative appearance and both resistance against white rust and red rust are improved.

Abstract: The invention relates to chromium- and cobalt-free treatment solutions for producing black coatings which afford corrosion protection. The treatment solution of the invention contains oxo cations or complex halogen ions or mixtures of oxo cations and complex halogen ions, an oxidant and an organic sulphur compound.

Abstract: 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, —SO3H, —NH2, —NHR, —NR2, —NR3+, and —COOH (wherein R is a C1-C6 alkyl group), (iii) 20 to 400 mmol/l Cr3+ and (iv) 50 to 2000 mmol/l NO3?. 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.

Abstract: The invention relates to a method for producing a coating layer protecting against corrosion wherein a surface which is to be treated is brought into contact with an aqueous treatment solution containing chromium(III) ions and at least one phosphate compound, wherein the ratio of the molar concentration of the chromium(III) ions to the molar concentration of the at least one phosphate compound (calculated as orthophosphate) lies between 1:1.5 and 1:3. The method improves the corrosion protection of metallic, in particular, zinc-containing, surfaces provided with conversion layers. The decorative and functional properties of the surface are maintained or improved. Furthermore, the known problems resulting from the use of chromium(VI)-containing compounds or from post-treatments with polymer dispersions are avoided.

Abstract: The invention relates to chromium- and cobalt-free treatment solutions for producing black coatings which afford corrosion protection. The treatment solution of the invention contains oxo cations or complex halogen ions or mixtures of oxo cations and complex halogen ions, an oxidant and an organic sulphur compound.

Abstract: Additives for electrolyte baths for the electrodeposition of zinc or zinc alloy layer are described. The additives are polymers with terminal amino groups. These polymers are obtainable by reaction of at least one diamino compound (having two tertiary amino groups) with at least one di(pseudo)halogen compound, wherein the diamino compound is used in stoichiometric excess. The additives effect, in particular, a very little formation of bubbles and only few burnings as well as a uniform distribution of layer thickness in the electrodeposition of zinc or zinc alloy layers.

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.

Abstract: The invention relates to a method for producing a coating layer protecting against corrosion wherein a surface which is to be treated is brought into contact with an aqueous treatment solution containing chromium(III) ions and at least one phosphate compound, wherein the ratio of the molar concentration of the chromium(III) ions to the molar concentration of the at least one phosphate compound (calculated as orthophosphate) lies between 1:1.5 and 1:3. The method improves the corrosion protection of metallic, in particular, zinc-containing, surfaces provided with conversion layers. The decorative and functional properties of the surface are maintained or improved. Furthermore, the known problems resulting from the use of chromium(VI)-containing compounds or from post-treatments with polymer dispersions are avoided.

Abstract: 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, —SO3H, —NH2, —NHR, —NR2, —NR3+, and —COOH (wherein R is a C1-C6 alkyl group), (iii) 20 to 400 mmol/l Cr3+ and (iv) 50 to 2000 mmol/l NO3?, 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 NO3? to Cr3+ is ?1, and (d) the following prerequisite is met (formula (I)), 0.