HK1138044B - Electrolyte and method for depositing decorative and technical layers of black ruthenium - Google Patents

Description

Electrolyte and method for depositing a decorative technical layer of black ruthenium

The invention relates to a ruthenium electrolyte which is suitable for depositing decorative technical layers having a specific blackness. Furthermore, the invention relates to a method for depositing decorative technical layers of ruthenium with a specific blackness ("black ruthenium") on items of jewelry, decorative items, consumer items and technical articles.

Consumer articles and technical articles, jewelry items and decorative articles are finished with thin oxidation-stable metal layers to avoid corrosion and/or to improve visual quality. These layers must be mechanically stable and should not show rust or marks even in the case of relatively long-term use. Attempted and tested means for producing these layers include electroplating processes by means of which various metal and alloy layers can be obtained with high quality. Well known examples of everyday life are electrodeposited bronze and brass layers on door handles or buttons, chromium coatings on vehicle parts, galvanized tools or gold coatings on watch straps.

A particular challenge in the field of electrochemical finishing is the production of oxidation-stable and mechanically robust ferrous metal layers, which can be of interest not only in the decorative and jewelry fields, but also for technical applications, for example in the field of solar engineering. Only some metals are available for producing the oxidation-stable black layer. In addition to ruthenium, rhodium and nickel are suitable. The use of rhodium, a noble metal, is limited to the jewelry field because of its high raw material cost. In particular in the field of jewellery and consumer goods, economical nickel and nickel-containing alloys can be used only in exceptional cases and in view of the demanding requirements, since nickel and nickel-containing metal layers are contact allergens. The use of ruthenium is a suitable alternative for all the fields of application described.

Electrolytes for producing black ruthenium layers in an electroplating process for finishing are known from the prior art. The most common baths contain ruthenium in the form of a complex with sulfamic acid or ruthenium in the form of a nitrilo-chloro or nitrilo-bromo complex

For example, JP63259095 discloses a method for electroplating ruthenium using a bath containing 5g/l ruthenium and 100-150g/l sulfamic acid. WO2001/011113 discloses ruthenium electrolytes containing ruthenium sulfate and sulfamic acid. Thio compounds are used as blackening additives. In order to protect the thio compound from decomposition by anodic oxidation, sacrificial materials must also be added. According to DE 19741990, an electrolyte for the electrochemical deposition of low-stress ruthenium layers with good tensile strength contains ruthenium and pyridine or N-alkylated pyridinium salts in the form of complexes with sulfamic acid. US4375392 claims an acidic electrolyte for the deposition of ruthenium on various substrates, containing a complex of ruthenium and sulfamic acid in a molar concentration of 4 to 10mol sulfamic acid per mol of ruthenium and at a suitable concentration, and containing a second compound of a metal selected from the group consisting of nickel, cobalt, iron, tin, lead and manganese. The concentration of the second metal is chosen so that a ruthenium layer with good tensile strength can be deposited. The bath has a pH of 0.1-2.2.

DE 1959907 discloses dinuclear ruthenium complexes [ Ru₂NCl_xBr_8-x(H₂O)₂]^3-Use in an electroplating bath. In one embodiment, a nitrilo chloro complex [ Ru ] is used₂NCl₈(H₂O)₂]^3-. This nitrogen-based chloro complex is also used in an aqueous non-acidic bath to electrodeposit ruthenium, as described in US 4297178. Oxalic acid or an oxalate salt is also present therein.

JP56119791 has as subject of the invention a ruthenium electrolyte which, in addition to containing from 1 to 20g/l of ruthenium, contains one or more selected from di-and tricarboxylic acids, benzenesulfonic acids, N-containing aromatics and amino acids or derivatives of said compounds, and furthermore, wherein from 0.01 to 10g/l of a thio compound is present as blackening additive.

JP2054792 preferably contains, In addition to an inorganic ruthenium salt, ruthenium sulfate, an inorganic acid, preferably sulfuric acid, and a "group III metal", preferably Sc, Y, In or Ga.

In order to finish jewelry and decorative articles, the black layer must not only have excellent mechanical adhesive strength, but must also have satisfactory visual quality. If desired, they must be produced in bright or dark form and with a very deep blackness. The same applies to the technical field, in particular to the application of solar engineering. Furthermore, the black layer of finished consumer goods must meet high requirements of mechanical stability. In particular, they do not exhibit any black abrasion over a relatively long period of time in the case of frequent use.

Ruthenium baths disclosed in the prior art and meeting these requirements either rely on the use of toxic, unsafe compounds, such as thio compounds, as blackening additives, or contain further transition metals to ensure the required mechanical bond strength, which complicates the handling of the bath during the deposition process.

It is therefore an object of the present invention to provide a non-toxic electrolyte for the deposition of ruthenium layers having a specific blackness ("black ruthenium"), by means of which, in standard electroplating methods, black layers can be produced which are characterized by a high mechanical stability, in particular with frequent use, by abrasion resistance, and moreover by the various blackness in order to maintain brightness.

This object is achieved by an electrolyte containing one or more phosphonic acid derivatives as blackening additives. Also provided is a process for applying decorative technical layers of ruthenium having a specific blackness ("black ruthenium") to jewelry items, decorative articles, consumer articles and technical articles by means of using the electrolyte according to the invention, wherein the substrate to be coated is immersed in the electrolyte according to the invention.

In the context of this document, "non-toxic" is understood to mean that the electrolyte according to the invention, so designed, does not contain substances classified as "toxic" (T) or "extremely toxic" (T) according to the regulations adopted in europe when handling hazardous materials and hazardous substances⁺) The substance of (1).

The ruthenium is used in the form of a water-soluble compound, preferably of the formula [ Ru₂N(H₂O)₂X₈]^3-The dinuclear, anionic nitrilo-halogenated complex compound of (1), wherein X is used in the form of a halide ion. Particular preference is given to chloro complexes [ Ru₂N(H₂O)₂Cl₈]^3-. The amount of complex compound in the electrolyte according to the invention is chosen so that, after complete dissolution of the compound, the volume concentration of ruthenium is between 0.2 and 20g per liter of electrolyte, calculated as ruthenium metal. The finished electrolyte particularly preferably contains from 1 to 15g of ruthenium/l of electricityThe electrolyte, very particularly preferably 3 to 10g of ruthenium per liter of electrolyte.

By suppressing the deposition rate from the electroplating bath in a targeted manner, blackening of the electrochemically produced ruthenium layer is achieved. One or more phosphonic acid derivatives are present as inhibitors and thus act as blackening additives in the baths of the present invention.

Compounds which are preferably used are aminophosphonic acid AP, 1-aminomethylphosphonic acid AMP, aminotri (methylenephosphonic acid) ATMP, 1-aminoethylphosphonic acid AEP, 1-aminopropylphosphonic acid APP, (1-acetylamino-2, 2, 2-trichloroethyl) -phosphonic acid, (1-amino-1-phosphooctyl) phosphonic acid, (1-benzoylamino-2, 2, 2-trichloroethyl) phosphonic acid, (1-benzoylamino-2, 2-dichlorovinyl) phosphonic acid, (4-chlorophenylhydroxymethyl) phosphonic acid, diethylenetriaminepenta (methylenephosphonic acid) DTPMP, ethylenediaminetetra (methylenephosphonic acid) EDTMP, 1-hydroxyethane (1, 1-diphosphonic acid) HEDP, hydroxyethylaminodi (methylenephosphonic acid) HEMPA, hexamethylenediaminetetra (methylphosphonic acid) HDTMP, ((hydroxymethylphosphomethylamino) methyl) phosphonic acid, nitrilotris (methylenephosphonic acid) NTMP, 2, 2, 2-trichloro-1- (furan-2-carbonyl) -aminoethylphosphonic acid, salts derived therefrom, or condensates derived therefrom, or combinations thereof.

Particularly preferred is one or more compounds selected from the group consisting of aminotris (methylenephosphonic acid) ATMP, diethylenetriamine penta (methylenephosphonic acid) DTPMP, ethylenediamine tetra (methylenephosphonic acid) EDTMP, 1-hydroxyethane (1, 1-diphosphonic acid) HEDP, hydroxyethylaminobis (methylenephosphonic acid) HEMPA, hexamethylenediamine tetra (methylphosphonic acid) HDTMP, salts derived therefrom or condensates derived therefrom, or combinations thereof.

Aminotris (methylenephosphonic acid) ATMP, ethylenediamine tetra (methylenephosphonic acid) EDTMP and 1-hydroxyethane (1, 1-diphosphonic acid) HEDP and salts derived therefrom or condensates derived therefrom, or combinations thereof, are particularly outstandingly suitable as coatings for decorative and consumer articles.

The concentration of the blackening additive determines the degree of blackness of the layer to be produced. The concentration must be chosen so as to achieve the desired degree of blackness, but not necessarily too high. If the concentration of the blackening additive is chosen too high, the current density at which the adhesion strength of the resulting ruthenium layer is no longer ensured must be chosen in order to ensure an economical deposition rate. The electrolyte according to the invention preferably contains from 0.1 to 20g of phosphonic acid derivative per l of electrolyte, particularly preferably from 1 to 10g of phosphonic acid derivative per l of electrolyte. If a dark grey colour other than darker black is to be achieved, then 0.1-4g of phosphonic acid derivative per l of electrolyte is preferred.

The phosphonic acid derivatives used have the effect of maintaining brightness. In all the variants, the color of the resulting layer can be adjusted from light black to dark black by suitable choice of the type and amount of phosphonic acid derivative without changing its characteristic brightness.

The pH of the bath of the invention has an important influence on the controllability of the electrolyte during the deposition process and on the quality of the resulting black ruthenium layer. It is preferably from 0 to 3, particularly preferably from 0.5 to 2. To establish the pH, the electrolyte of the present invention may contain a mineral acid, preferably selected from the group consisting of hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, nitrous acid, amidosulfonic acid, sulfuric acid, sulfurous acid, pyrosulfuric acid, dithionic acid, pyrosulfurous acid, and dithionous acid, or a combination thereof. Hydrochloric, hydrobromic, amidosulfonic and sulfuric acids or combinations thereof are particularly suitable. Depending on the phosphonic acid derivative used and the concentration in which it is used and the mineral acid chosen, the preferred volume concentration of the mineral acid is from 0 to 50g/l of electrolyte, particularly preferably from 0 to 40g/l of electrolyte. Electrolytes particularly suitable for depositing uniform decorative black ruthenium layers contain 1-10g sulfuric acid per liter of electrolyte.

In addition to ruthenium and phosphonic acid derivatives, the electrolyte may also contain organic additives which function as wetting agents. Preferably one or more compounds selected from the group consisting of alkanesulfonic acids or ionic and nonionic surfactants or combinations thereof are added. Alkanesulfonic acids are particularly suitable.

The bath of the invention is suitable for depositing pure ruthenium layers, but not for depositing ruthenium alloys. The electrolyte does not contain transition metal ions other than ruthenium.

The ruthenium electrolyte described, which is the subject of the present invention, is particularly suitable for depositing decorative, dark and bright layers, for example on jewelry items and decorative items. It can preferably be used in drum and rack (rack) coating processes.

In a corresponding method for the electrochemical application of black ruthenium layers, the pieces of jewelry, decorative articles, consumer articles or technical articles to be coated (together collectively referred to as substrates) are immersed in the electrolyte of the invention and form a cathode. The electrolyte is preferably thermostatted in the range from 20 to 80 ℃. In particular, the decorative layer is obtained at an electrolyte temperature of 60-70 ℃.

In order to obtain a strongly bonded uniform layer, the maximum current density should not exceed 10A/dm²[A/dm²]. Beyond this value, amorphous portions of ruthenium are deposited. As a result, the layer becomes inhomogeneous and shows dark-colored abrasion under mechanical load. Preferably, a current density of 0.01-10A/dm is established²Particularly preferably 0.05 to 5A/dm². The selected value is also determined by the type of coating method. In the drum coating method, the preferred current density is 0.05-1A/dm². In the stent coating method, 0.5-5A/dm²The current density of (a) results in a visually satisfactory black ruthenium layer.

Insoluble anodes are suitable for electrochemical deposition processes from the acidic ruthenium baths of the present invention. Anodes preferably used are those comprising a material selected from the group consisting of platinized titanium, graphite, iridium transition metal mixed oxide and special Carbon material ("Diamond Like Carbon" DLC) or combinations thereof.

The following examples are intended to explain the invention in more detail:

example 1:

the electrolyte of the present invention contains 2.5g/l of [ Ru₂NCl₈(H₂O)₂]^3-In addition to ruthenium in the form, 15g/l of 1-hydroxyethane (1, 1-diphosphonic acid) HEDP dissolved in water was also included as a blackening additiveAdditives, and 20g/l sulfuric acid were used to deposit a black layer on consumer goods. The pH of the electrolyte was 0.8.

In the stent coating method, the coating is carried out at 2-10A/dm²A suitable substrate is coated at a current density in which the electrolyte is thermostatted at 60 ℃.

After the deposition process is complete, the substrate has a mechanically stable abrasion-resistant black layer, which is considered visually satisfactory in the field of consumer goods. Slight irregularities in the layer thickness of the resulting layer limit the application of this bath of the invention to applications outside the jewelry field.

Example 2:

containing 5g/l of [ Ru₂NCl₈(H₂O)₂]^3-Ruthenium in the form and 1.5g/l ethylenediamine tetra (methylenephosphonic acid) EDTMP in water as an electrolyte for the blackening additive were used for producing black ruthenium layers on decorative articles. 4g/l sulfuric acid was added to the electrolyte to determine the pH so that the pH at the start of deposition was 1.3.

In the bracket device, the length is between 0.5 and 3A/dm²A suitable substrate was finished with a black ruthenium layer at a set current density. During the deposition process, the electrolyte is kept at a constant temperature of 60-70 ℃.

The resulting layer has very good mechanical stability and exhibits a deep black color and a large brightness. The visual quality of the layer thus produced is so high that the bath according to the invention is also suitable for the jewelry and decoration field.

Example 3:

study of a composition containing 5g/l in [ Ru₂NCl₈(H₂O)₂]^3-Further bath according to the invention of ruthenium in the form and 5g/l of aminotri (methylenephosphonic acid) ATMP in water. The pH was adjusted to 1.4 using 4g/l sulfuric acid.

In the stent coating method, the coating thickness is 0.5 to 2.5A/dm²At the set current density and in a constant temperature bath at 60 c, a dark black layer of high visual quality is likewise obtained.

Claims (13)

1. Non-toxic electrolyte for the deposition of decorative technical layers with black ruthenium, characterized in that the electrolyte contains one or more phosphonic acid derivatives as blackening additives and the mass concentration of ruthenium is 0.2 to 20g/l electrolyte, calculated as ruthenium metal.

2. The electrolyte as claimed in claim 1, characterized in that the ruthenium has the formula [ Ru₂N(H₂O)₂X₈]^3-In the form of a dinuclear, anionic ruthenium-nitrilo halogenated complex compound.

3. The electrolyte of claim 2, characterized in that the electrolyte is free of other transition metal ions.

4. Electrolyte according to claim 2, characterized in that it contains as phosphonic acid one or more compounds selected from the group consisting of: aminophosphonic acid AP, 1-aminomethylphosphonic acid AMP, aminotri (methylenephosphonic acid) ATMP, 1-aminoethylphosphonic acid AEP, 1-aminopropylphosphonic acid APP, (1-acetylamino-2, 2, 2-trichloroethyl) -phosphonic acid, (1-amino-1-phosphoric acid octyl) phosphonic acid, (1-benzoylamino-2, 2, 2-trichloroethyl) phosphonic acid, (1-benzoylamino-2, 2-dichlorovinyl) phosphonic acid, (4-chlorophenylhydroxymethyl) phosphonic acid, diethylenetriamine penta (methylenephosphonic acid) DTPMP, ethylenediamine tetra (methylenephosphonic acid) EDTMP, 1-hydroxyethane (1, 1-diphosphonic acid) HEDP, hydroxyethylaminodi (methylenephosphonic acid) HEMPA, hexamethylenediamine tetra (methylenephosphonic acid) HDTMP, ((hydroxymethyl phosphomethylamino) methyl) phosphonic acid, nitrilotris (methylenephosphonic acid) NTMP, 2, 2, 2-trichloro-1- (furan-2-carbonyl) -aminoethylphosphonic acid, salts derived therefrom or condensates derived therefrom, or mixtures thereof.

5. Electrolyte according to claim 4, characterized in that it contains 0.1 to 20g of phosphonic acid derivative per liter of electrolyte.

6. Electrolyte according to claim 4, characterized in that the pH of the electrolyte is between 0 and 3.

7. The electrolyte of claim 6, characterized in that the electrolyte contains an inorganic acid selected from the group consisting of: hydrochloric, hydrobromic, hydroiodic, nitric, nitrous, amidosulfonic, sulfuric, sulfurous, pyrosulfuric, dithionic, pyrosulfurous, and dithionous acids, or mixtures thereof.

8. Electrolyte according to any of claims 4 to 7, characterized in that the electrolyte contains as wetting agent one or more compounds selected from alkanesulfonic acids or ionic and nonionic surfactants or mixtures thereof.

9. Method for electrochemically applying decorative technical layers with black ruthenium to jewelry items, decorative articles, consumer articles and technical articles, wherein a substrate to be coated is immersed in an electrolyte containing ruthenium in dissolved form, characterized in that an electrolyte is used which contains one or more phosphonic acid derivatives as blackening additives.

10. A method according to claim 9, characterised in that the electrolyte is thermostatted in the range 20-80 ℃.

11. The method of claim 10, characterized in that the range of 0.01 to 10 amperes per decimeter is established²The current density of (1).

12. Method according to claim 11, characterized in that an insoluble anode is used, which comprises a material selected from the group consisting of platinized titanium, graphite, iridium transition metal mixture oxides and special carbon materials or mixtures of these anodes.

13. The method of claim 12, characterized in that the specialty carbon material is diamond-like carbon.