Disclosed is an electrolyte for the electrolytic deposition of chromium as a metal, comprising (a) a chromium (III) salt and (b) metallic chromium, the use of the electrolyte for producing chromium layers on rotationally symmetrical components, in particular gravure printing cylinders, and methods, in which this electrolyte is used.

Disclosed is an electrolyte for the electrolytic deposition of chromium as a metal, comprising (a) a chromium (III) salt and (b) metallic chromium, the use of the electrolyte for producing chromium layers on rotationally symmetrical components, in particular gravure printing cylinders, and methods, in which this electrolyte is used.

In a method for passivating the surface of a tinplate using electrolytic deposition of a passivation layer containing chromium oxide/chromium hydroxide on the surface, the electrolytic deposition of the passivation layer is carried out at least partly from an electrolyte solution which contains a trivalent chromium compound, at least one salt for increasing the conductivity and at least one acid or one base for adjusting a desired pH value and is free from organic complexing agents and free from buffering agents. In order to increase the amount of chromium oxide in the passivation layer, after the electrolytic deposition of the passivation layer, the passivated tinplate is subjected to a thermal treatment in which the passivated tinplate is kept at a treatment temperature of 100° C. or more for a treatment time of at least 0.5 seconds.

In a method for passivating the surface of a tinplate using electrolytic deposition of a passivation layer containing chromium oxide/chromium hydroxide on the surface, the electrolytic deposition of the passivation layer is carried out at least partly from an electrolyte solution which contains a trivalent chromium compound, at least one salt for increasing the conductivity and at least one acid or one base for adjusting a desired pH value and is free from organic complexing agents and free from buffering agents. In order to increase the amount of chromium oxide in the passivation layer, after the electrolytic deposition of the passivation layer, the passivated tinplate is subjected to a thermal treatment in which the passivated tinplate is kept at a treatment temperature of 100° C. or more for a treatment time of at least 0.5 seconds.

An object comprising a chromium-based coating on a substrate is disclosed. The chromium is electroplated from an aqueous electroplating bath comprising trivalent chromium cations, wherein the chromium-based coating comprises: a first chromium-containing layer, on the substrate, having a thickness of at least 100 nm, and a Vickers microhardness value of 700-1000 HV; a second chromium-containing layer, on the first chromium-containing layer, having a Vickers microhardness value that is at least 1.3 times higher than the Vickers microhardness value of the first chromium-containing layer, and a crystal size of 8-35 nm; and wherein the chromium-based coating exhibits a critical scratch load value (L.sub.c2) of at least 60 N in the adhesion test according to ASTM C1624-05 (2015; point 11.11.4.4), and wherein the chromium-based coating does not contain chromium carbide. Further is disclosed a method for its production.

An object comprising a chromium-based coating on a substrate is disclosed. The chromium is electroplated from an aqueous electroplating bath comprising trivalent chromium cations, wherein the chromium-based coating comprises: a first chromium-containing layer, on the substrate, having a thickness of at least 100 nm, and a Vickers microhardness value of 700-1000 HV; a second chromium-containing layer, on the first chromium-containing layer, having a Vickers microhardness value that is at least 1.3 times higher than the Vickers microhardness value of the first chromium-containing layer, and a crystal size of 8-35 nm; and wherein the chromium-based coating exhibits a critical scratch load value (L.sub.c2) of at least 60 N in the adhesion test according to ASTM C1624-05 (2015; point 11.11.4.4), and wherein the chromium-based coating does not contain chromium carbide. Further is disclosed a method for its production.

To provide a trivalent chromium plating film, in which the generation of cracks penetrating from the film surface to a substrate interface is suppressed, and a sliding member coated with the trivalent chromium plating film, plating is conducted with a chromium plating bath containing trivalent chromium as a chromium source, with a second phase dispersed in a planar and/or fibrous form, such that the second phase in a planar and/or fibrous form is dispersed in the hard chromium plating film to prevent or deflect the propagation of cracks, and to suppress the increase of the crack width, thereby suppressing the propagation of cracks in the hard chromium plating film.

To provide a trivalent chromium plating film, in which the generation of cracks penetrating from the film surface to a substrate interface is suppressed, and a sliding member coated with the trivalent chromium plating film, plating is conducted with a chromium plating bath containing trivalent chromium as a chromium source, with a second phase dispersed in a planar and/or fibrous form, such that the second phase in a planar and/or fibrous form is dispersed in the hard chromium plating film to prevent or deflect the propagation of cracks, and to suppress the increase of the crack width, thereby suppressing the propagation of cracks in the hard chromium plating film.

The present invention relates to a very specific electroplating bath for depositing a black chromium layer, a respective method thereof, and a respective substrate with said black chromium layer thereon. The substrate comprising said black chromium layer is excellently suited for decorative purposes.

The present invention relates to a very specific electroplating bath for depositing a black chromium layer, a respective method thereof, and a respective substrate with said black chromium layer thereon. The substrate comprising said black chromium layer is excellently suited for decorative purposes.