Abstract: The present invention relates to a method for forming a black-passivation layer on a zinc-iron alloy of a substrate, a black-passivation composition for depositing a black-passivation layer on such, in which the black-passivation composition includes one or more than one blackening agent selected from the group consisting of formula (I) and formula (II) as described hereinafter, and a respective use of said blackening agents for blackening a zinc-iron alloy.

Abstract: The present invention is related to an aqueous post treatment composition for providing a post treatment layer on at least a part of a passivation layer, which is covering at least a part of a zinc layer being on at least a part of an iron containing substrate, characterized in that the aqueous post treatment composition comprises at least one chromium (III) ion source and at least one compound containing the chemical element silicon; wherein a molar ratio of silicon versus chromium is given in said composition, with the proviso that said molar ratio is ranging from 2600:1 to 1:1 for the zinc layer obtained by an electrolytic acid zinc deposition process; or that said molar ratio is ranging from 5200:1 to 1:1 for the zinc layer obtained by an electrolytic alkaline zinc deposition process.

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 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 a method for coating metallic surfaces with an aqueous composition as a solution or as a dispersion, wherein the composition contains a) at least one phosphate, b) at least 0.1 g/L of at least one titanium and/or zirconium compound, c) at least one complexing agent, d) cations of aluminum, chromium(III), and/or zinc and/or at least one compound containing aluminum, chromium(III), and/or zinc, and e) 1 to 500 g/L of at least one acid-tolerant cationic or nonionic organic polymer/copolymer, relative to the content of the solids and active substances in these additives.