An aqueous trivalent chromium electrolyte comprising trivalent chromium ions and amino acids that allow for producing a dark colored hue in the trivalent chromium coating which is plated on a substrate. The amino acids described herein comprise a cationic side chain and are at least essentially free of sulfur. The cationic side chain of the amino acid further comprises nitrogen. When used in the trivalent chromium electrolyte, these amino acids allow for producing significantly darker trivalent chromium deposits. The trivalent chromium electrolyte is used in a method for producing the desired dark colored hue in the trivalent chromium coating that is produced on a substrate using electrodeposition.

A metal material having thermodynamic anisotropy has an X-axis hardness of 160-180 HV, an X-axis hardness thermal expansion coefficient of 5×10-6-100×10-6 K.sup.−1; a Y-axis hardness of 160-180 HV, a Y-axis hardness thermal expansion coefficient of 5×10-6-100×10-6 K.sup.−1; and a Z-axis hardness of 180-250 HV, a Z-axis hardness thermal expansion coefficient of 50×10-6-1000×10-6 K.sup.−1. A method for preparing a metal material having thermodynamic anisotropy is also disclosed.

The invention consists of a chromium electroplating solution comprising a chromium electroplating solution comprising: (1) a water soluble trivalent chromium salt; (2) at least one complexant for trivalent chromium ions; (3) a source of hydrogen ions sufficient to create a pH of from 2.8-4.2; (4) a pH buffering compound; and (5) a sulfur-containing organic compound. The chromium electroplating solution is usable in a method for producing an adherent metallic coating on a decorative article, such coating having enhanced resistance to corrosion in environments containing calcium chloride.

The invention consists of a chromium electroplating solution comprising a chromium electroplating solution comprising: (1) a water soluble trivalent chromium salt; (2) at least one complexant for trivalent chromium ions; (3) a source of hydrogen ions sufficient to create a pH of from 2.8-4.2; (4) a pH buffering compound; and (5) a sulfur-containing organic compound. The chromium electroplating solution is usable in a method for producing an adherent metallic coating on a decorative article, such coating having enhanced resistance to corrosion in environments containing calcium chloride.

A black plated resin part includes a resin substrate, an underlying plating layer formed on the resin substrate, and a black chromium plating layer formed of trivalent chromium and having a thickness of 0.15 μm or more. The black chromium plating layer is formed on the underlying plating layer. The chromium in the black chromium plating layer is present in the form of metallic chromium, chromium oxide, and chromium hydroxide, and the black chromium plating layer exhibits a b* value of 3.0 or less based on the L*a*b* color system.

A metal material having thermodynamic anisotropy has an X-axis hardness of 160-180 HV, an X-axis hardness thermal expansion coefficient of 5×10-6-100×10-6 K.sup.−1; a Y-axis hardness of 160-180 HV, a Y-axis hardness thermal expansion coefficient of 5×10-6-100×10-6 K.sup.−1; and a Z-axis hardness of 180-250 HV, a Z-axis hardness thermal expansion coefficient of 50×10-6-1000×10-6 K.sup.−1. A method for preparing a metal material having thermodynamic anisotropy is also disclosed.

A method for preparing a Cr(III)-plating solution is disclosed. The method comprises or consists of the steps of (a) providing an aged aqueous Cr(III)-solution; (b) adding a polycarbonate or a derivative thereof to the solution of step (a); and (c) adding a borate to the solution of step (b). In addition, a plating solution obtainable by the present method is disclosed, and a plating solution comprising or consisting of Cr(III)-ions, a polycarbonate or a derivative thereof, a borate, water, sulfate, and positive ions selected from the group consisting of hydrogen ions, alkali metal ions and earth alkali metal ions.

A method for preparing a Cr(III)-plating solution is disclosed. The method comprises or consists of the steps of (a) providing an aged aqueous Cr(III)-solution; (b) adding a polycarbonate or a derivative thereof to the solution of step (a); and (c) adding a borate to the solution of step (b). In addition, a plating solution obtainable by the present method is disclosed, and a plating solution comprising or consisting of Cr(III)-ions, a polycarbonate or a derivative thereof, a borate, water, sulfate, and positive ions selected from the group consisting of hydrogen ions, alkali metal ions and earth alkali metal ions.

A method for the electrodeposition of a functional or decorative chromium layer onto a metallic substrate in an electrodeposition process from a halide-ion free and boric acid free aqueous electrolyte solution and to the coated product obtained thereby.

A method for the electrodeposition of a functional or decorative chromium layer onto a metallic substrate in an electrodeposition process from a halide-ion free and boric acid free aqueous electrolyte solution and to the coated product obtained thereby.