An apparatus for maintaining trivalent chromium plating bath efficiency includes an aqueous electroplating bath, which includes trivalent chromium ions and a sulfur compound, and an ultraviolet (UV) radiation source that provides UV radiation to the bath effective to inhibit a reduction in plating efficiency of the bath.

The invention relates to a method for the adjustment of the lightness L* of electrolytically deposited chromium-finishes on workpieces obtained by an electroplating bath comprising at least chromium(III)-ions and sulfur containing organic compounds, wherein the concentration of the sulfur containing organic compounds in the bath are adjusted by passing at least part of the bath composition through an activated carbon filter. Furthermore, the invention is directed to dark chrome coatings comprising a defined concentration gradient of deposited sulfur containing organic compounds.

The invention relates to a method for the adjustment of the lightness L* of electrolytically deposited chromium-finishes on workpieces obtained by an electroplating bath comprising at least chromium(III)-ions and sulfur containing organic compounds, wherein the concentration of the sulfur containing organic compounds in the bath are adjusted by passing at least part of the bath composition through an activated carbon filter. Furthermore, the invention is directed to dark chrome coatings comprising a defined concentration gradient of deposited sulfur containing organic compounds.

An apparatus for maintaining trivalent chromium plating bath efficiency includes an aqueous electroplating bath, which includes trivalent chromium ions and a sulfur compound, and an ultraviolet (UV) radiation source that provides UV radiation to the bath effective to inhibit a reduction in plating efficiency of the bath.

The present invention relates to an aqueous passivation solution having a pH in the range from 5.4 to 7.2, the solution including trivalent chromium ions, and formate anions and/or oxalate anions as complexing agents for said trivalent chromium ions, in which the trivalent chromium ions with respect to all formate anions together with all oxalate anions form a molar ratio in the range from 1:15 to 1:400.

A metal material having thermodynamic anisotropy has an X-axis hardness of 160-180 HV, an X-axis hardness thermal expansion coefficient of 510-6-10010-6 K.sup.1; a Y-axis hardness of 160-180 HV, a Y-axis hardness thermal expansion coefficient of 510-6-10010-6 K.sup.1; and a Z-axis hardness of 180-250 HV, a Z-axis hardness thermal expansion coefficient of 5010-6-100010-6 K.sup.1. A method for preparing a metal material having thermodynamic anisotropy is also disclosed.

According to the method for producing chromium plated parts, a plurality of workpieces are immersed in a chromium plating bath, a plating treatment is performed by using a pulse current, and chromium plating layers that have compressive residual stress and suppressed cracking are deposited on surfaces of the plurality of workpieces. A direct current from plating separation lower limit current density up to a range in which the chromium plating layers have compressive residual stress is superimposed during downtime of application of the pulse current.

According to the method for producing chromium plated parts, a plurality of workpieces are immersed in a chromium plating bath, a plating treatment is performed by using a pulse current, and chromium plating layers that have compressive residual stress and suppressed cracking are deposited on surfaces of the plurality of workpieces. A direct current from plating separation lower limit current density up to a range in which the chromium plating layers have compressive residual stress is superimposed during downtime of application of the pulse current.

According to the method for producing chromium plated parts, a plurality of workpieces are immersed in a chromium plating bath, a plating treatment is performed by using a pulse current, and chromium plating layers that have compressive residual stress and suppressed cracking are deposited on surfaces of the plurality of workpieces. A direct current from plating separation lower limit current density up to a range in which the chromium plating layers have compressive residual stress is superimposed during downtime of application of the pulse current.

According to the method for producing chromium plated parts, a plurality of workpieces are immersed in a chromium plating bath, a plating treatment is performed by using a pulse current, and chromium plating layers that have compressive residual stress and suppressed cracking are deposited on surfaces of the plurality of workpieces. A direct current from plating separation lower limit current density up to a range in which the chromium plating layers have compressive residual stress is superimposed during downtime of application of the pulse current.