Electrolyte for the Deposition of Anthracite/Black Rhodium/Ruthenium Alloy Layers

Abstract

The present invention is directed toward an electrolyte which allows for electrolytically producing a black metal layer consisting of rhodium and ruthenium. The present invention also relates to a method for producing a corresponding article, and to the use of the electrolyte.

Claims

1. An aqueous, acidic electrolyte for producing dark metal layers on conductive materials, comprising: 0.5-15.0 g/l of a soluble rhodium compound (in relation to the metal); 0.5-10.0 g/l of a soluble ruthenium compound (in relation to the metal); 5-150 g/l of an acid; and a phosphonic acid and a dicarboxylic acid.

2. The electrolyte according to claim 1, wherein the ruthenium is present as a binuclear complex in the electrolyte.

3. A method of producing an article having an electrodeposited metal layer comprising the metals rhodium and ruthenium in a wt %-based composition of from 40:60 to 90:10, based on the sum of the weights of both metals, the metal layer having an L* value of less than 65 and an a* value of from −3 to +3 according to the Cielab color system (EN ISO 11664-4, newest version as of the application date), which comprises using the electrolyte according to claim 1 to deposit the electrodeposited metal layer on the article.

4. The method according to claim 3, wherein the b* value of the metal layer is between −7 and +7.

5. The method according to claim 3, wherein the metal layer serves as an underlayer for a further electrodeposited metal layer of rhodium, the latter having a thickness of 0.05-0.5 μm.

6. The method according to claim 5, wherein the L* value of the layer sequence is below 50.

7. The method according to claim 3, wherein the produced metal layer(s) has/have an abrasion resistance of less than 0.75 μm/1000 strokes (in the Bosch-Weinmann test).

8. A method for electrodepositing a metal layer on a conductive material, which comprises a) contacting the conductive material as a cathode with an aqueous, acidic electrolyte according to claim 1; b) contacting an anode with the electrolyte; and c) establishing a current flow between the cathode and the anode.

9. The method according to claim 8, wherein the current density in the electrolyte is 0.1-50 A/dm.sup.2.

10. The method according to claim 8, wherein the pH value of the electrolyte is between 0.2 and 2.

11. The method according to claim 8, wherein the temperature during electrolysis is between 20° C. and 65° C.

12. The method according to claim 8, and further comprising subjecting the deposited metal layer to anodic post-treatment.

Description

EXAMPLE 1

[0046] An electrolyte according to the invention which, in addition to 1.5 g/l of rhodium [dirhodium trisulfate], also contained 0.5 g/l of ruthenium as [Ru.sub.2NCl.sub.8(H.sub.2O).sub.2].sup.3−, 4 g/l of ethylene diamine tetra (methylene phosphonic acid) EDTMP, and 11 g/l of potassium hydrogen phtalate as a blackening agent in water, and 10 g/l of sulfuric acid, was used for producing black, well-conductive, and abrasion-resistant layers on consumer goods. The temperature of the electrolyte was 45° C.; the pH around 1.0.

[0047] In a rack coating process, suitable substrates were finished at a set current density of 0.25 to 5 A/dm.sup.2. The obtained layers had very good mechanical stability and exhibited a black, very appealing neutral hue in the color range (a* and b* value).

[0048] The color values are visible in the appended diagrams (FIGS. 1-3). The electrolyte according to the invention is referred to as RA black.

[0049] Ruthuna® 490 and Ru 479 are commercially available black ruthenium electrolytes. Rhoduna® 470 and 471 are commercially available black rhodium electrolytes (https://ep.umicore.com/en/products/productfinder).

EXAMPLE 2

[0050] An electrolyte according to the invention which, in addition to 1.0 g/l of rhodium [dirhodium trisulfate], also contained 1.0 g/l of ruthenium as [Ru.sub.2NCl.sub.8(H.sub.2O).sub.2].sup.3−, 5 g/l of ethylene diamine tetra (methylene phosphonic acid) EDTMP, and 7.5 g/l of potassium hydrogen phtalate as a blackening agent in water, and 10 g/l of sulfuric acid, was used for producing particularly black and abrasion-resistant layers on consumer goods. The temperature of the electrolyte was 45° C.; the electrolyte had a pH value of about 1.2.

[0051] In a rack coating process, suitable substrates were pre-coated at a set current density of 0.75 to 2 A/dm.sup.2. A thin cover layer of a very dark (L*=47) black rhodium electrolyte (e.g. Rhoduna® 470) was then applied. It was anodically post-treated in a solution containing 10 g/l of potassium hydrogen phtalate at 4 volts. The post-dip solution was tempered at 30° C. The obtained layers showed a deep black hue and had very good mechanical stability.