DE3347594A1 - Bath for electrodepositing a wear-resistant gold alloy and process for depositing a wear-resistant gold alloy using said bath - Google Patents

Abstract

The electroplating gold alloy baths disclosed for decorative coatings have a pH of 0.75 to 2.75. The gold is present as alkali-metal auricyanide, while the alloying element is present as a water-soluble salt and the acid matrix is selected from the group comprising oxalic acid, citric acid, sulphamic acid, phosphoric acid, nitric acid and hydrochloric acid. The alloys can be deposited on electronic and decorative substrates in a relatively short time. The colour of the coating can be determined by variation of the pH and the choice of the alloying element. Wear-resistant coatings are obtained if the alloying element is cobalt or nickel. These baths contain nitric acid and an alkali-metal nitrate or phosphoric acid and, optionally, a wetting agent, and they have a pH not exceeding 0.75. The coatings are notable for an improved wear resistance, lower contact resistance and a lower content of concomitantly deposited carbon.

Description

The invention relates to a bath and a method for galvanic deposition of a decorative Goldlegiorun / js coating, wherein trivalent gold is used as a source of gold in an acid matrix in the bath. More precisely relates the invention relates to an electroplating bath containing trivalent gold, from which shiny gold alloy coatings are formed various substrates of the jewelry and decoration area can be preserved in tendon separation and from which Achieve different coating colors simply by controlling the bath composition and / or the electroplating conditions permit.

The invention also relates to an improved galvanic gold alloy bath in which the alloying element is cobalt or nickel, and to a method for Deposit a gold alloy coating using this bath. More precisely, this aspect of the invention is on a gold alloy bath, and a method of depositing one Gold alloy coating on various substrates in the electronic and jewelry and decoration field directed to coatings with improved mechanical properties such as improved wear resistance, increased> thermal stability, to produce decreased contact resistance, increased ductility and the like.

BATH ORIGINAL

yj OM- / V ^ **

kt W -ώ m »r ■» * Μι * -α ψ 4t * «J tt

w * V · 4 »fc # It%> β

8 «V * * WM W K)« *

With the usual electroplating systems for decorative Gold alloy coatings in which the gold plus monovalent, Au (l) -, is present, electrodeposition can be a 'thickness on the order of 0.00254 mm in about 15 minutes for one Current density of 1.08 A / dm can be generated. A well-known system for the deposition of a gold alloy from an Au (l) -containing bath is known, for example, from US Pat. No. 2,905,601 * attempts, " Improving the rate of deposition by increasing the current density has been unsuccessful. On the one hand let themselves be with no gold coatings on the paints in the rapid deposition baths that are required in the jewelry industry. on the other hand the resulting gold alloy coatings became dull when the pH of the bath increased the rate of deposition was increased.

In other processes for galvanic gold deposition that are industrially carried out today, an aqueous bath is used, in which the gold is monovalent positive and the metallic hardening agents are cobalt or nickel. With such a System in which cobalt and nickel are used in the form of their citrates, one can get hard, abor brittle gold alloy coatings receive an internal tensile stress with a Have a tendency to form microcracks. It has also been found that when the gold alloy is deposited from the cyanide-citrate system the co-deposition of carbon up to 0.2 Weight .- $> or above * can achieve »This can cause bad heat-

Stability above 150 ° C with the formation of undesirable fractures and / or result in bubbles in the deposited coating. The wear resistance is measured on coatings with a thickness of 2.5 µm after surviving 2000 passes on the crosshair tester, in two cycles per minute with a load of 200 g. and proceeding, valued.

Previously, the deposition of gold from baths in which the gold is in the trivalent positive state, Au (III) - has been proposed. Mohrnhein in Plating HS ^ (10) 1104 (1961) describes the use of the tetracyanoaurate (III) ion complex in an electroplating system. The complex was formed in situ by the stoichiometric neutralization of the chloroaurate (III) acid with potassium hydroxide and the addition of potassium cyanide. A mixture of three salts was used to buffer the solution. At temperatures of 60 ° C. and current densities in the range from 0.02 to 0.22 A / dm, glossy, firmly adhering finely crystalline coatings were obtained. The structure was ascribed to the presence of the chlorine ions.

Knoedler et al., Plating, 5% ( ⁶ ) 7 ^ 5 (1966) and Knoedler, Metalloberfläche, ^ (7), 269 (1979), examined the properties of the cyanoaurate (III) complex in galvanic solutions, there were several Conclusions were drawn showing: a) that the rate at which the Au (IIl) -

complex tends to convert to the Au (l) complex, with increasing pH increases and temperature increases; b) that in

... / 10 ORIGINAL BATHROOM

Presence of metallic gold of the cyanoaurate (JIl) complex and free cyanide form the cyanoaurate (l) ~ what the use does not make gold anodes seem appropriate; and c) that at low voltages the cathodic reduction to monovalent gold takes place preferably in acidic solutions and those that do not contain free cyanide the redox potential shifts towards more positive values.

US Pat. No. 3,598,706 "discloses a bath for the electrodeposition of gold and gold alloys using the cyanoaurate (III) complex. The preferred form was the cyanoauric acid instead of the potassium or sodium salt because of the advantage that in Operation of the bath no alkali metal hydroxide is formed The solution was at a pH value below 3, preferably at 1.5 using citric acid and phosphoric acid, at current densities between 0.22 and 0.93 A / dm and at temperatures between 35 ^un d 50 C. The solution was buffered with a compound from the group consisting of citrates, phosphates and tartrates. When using the cyanoaurate (III) salt, however, this contained a variable amount of the Au (I) complex and this was always the case, regardless of which method was used to prepare the Au (III) salt: The cyanoaurate (i) complex decomposes with precipitation of AuCN at the low pH value, which is required for optimal deposition conditions is required.

, .. / 11

BATH ORIGINAL

US Pat. No. h 16S 21 * l · discloses aqueous gold and gold alloy baths with a low pH value which contain a cyanoaurate (III) complex which was formed in situ. To aurichloride or auric acid, an excess of less than 15 / ° above the stoichiometric amount of alkali metal cyanide is added in order to prevent the formation of the Au (I) oxidation stage and the subsequent precipitation of aurocyanide. Hydrochloric acid is used to acidify the matrix and a water soluble metal chloride is added as an alloying element. Ethylenediamine and alkali metal nitrate are also added to improve conductivity. The last-mentioned compound reacts with the acid to form ethylenediamine hydrochloride, which is a convenient source of chlorine ions. The PS is directed to the electrodeposition of gold on inactivated stainless steel, and it has been believed that the presence of the chlorine and nitrate ions in an acidic medium would provide a dilute aqua-like composition which would adequately prepare such a surface.

The systems described above have several disadvantages. The production of the electroplating bath requires several Reaction stages. In addition, the presence of the Chlorine ions result in the formation of chlorine gas at the anode and lead to an environmental problem when pulse plating must be considered. Instability of the added organic compounds must be taken into account.

... / 12

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•. · * 41 H 9 + * ο

From an overview of the oinsclilHffi ^ en literature, sick certain criteria for any proposed method, in which Au (IIl) - is used. XTm the cyano-Au (Hl) complex an acidic solution is required to keep it stable; at pH values below about 3, however, the Au (I) complex falls as aurocyanide and therefore the solution must be completely free from Au (l) - to be. In addition, a solution that does not contain chloride is obviously quite useful.

The invention is based on the object of a bath for galvanic To indicate the deposition of a gold alloy that contains Au (IIl), is stable, and leads to wear-resistant coatings allows easy control of the color of the coatings obtained. The bath is said to be nickel or cobalt as the alloying element containing the problems associated with using nickel and cobalt hardening components Au (I) - should also be avoided. In addition, a process for the galvanic deposition of wear-resistant gold alloys should be used can be specified using this bath.

The object is achieved by the bath of claim 1 and the method of claim 16 solved. Preferred Embodiments are specified in the subclaims, -The invention provides an improved galvanic gold bath. It is an aqueous solution which contains: as a source for the gold an alkali metal Au (III) cyanide in one for the deposition of a

... / 13

Ot = IIGINAL

Gold plating on a substrate during electrolyzing the bath in sufficient amount; a water soluble inorganic Salt of an alloying element in an amount that is at least is enough to give the desired color to the gold plating; and an organic or inorganic acid matrix from the group Oxalic acid, citric acid, sulfamic acid, phosphoric acid, salic acid pitric acid and hydrochloric acid. The aqueous solution has a pH ¥ ert · above 0.75 and below 2.75 · Exemplary alloying elements, which can be used in the baths of the invention include: nickel, cobalt, copper, indium, zinc and tin; these metals are introduced into the bath in the form of their water-soluble inorganic salts.

When operating the galvanic baths according to the invention by changes in the pH value and / or the alloying element and / or the acid matrix produces gold coatings that have different colors but the same gold content. So can a galvanic bath, as described above, at a pH value within the specified range for separating a Coating of a certain appearance (color) can be operated and by increasing or decreasing the pH value within the specified area can be a plating with practically the same gold content, but completely different appearance (different color) getting produced. Similar changes in the appearance or color of the coating with no appreciable change in gold content can be changed by changing the alloying element and / or the

BATHROOM ORIGINAL

W W "I" V

the acid matrix can be generated. This way you can now the advantages of an Au (III) system, including increased deposition rate, in the deposition of decorative Gold plating can be realized.

Regarding the aspect of creating wear-resistant gold coatings it has been found that an improved Au (III) bath by using an aqueous bath of pH not above about 0.75 which contains: an alkali metal lauricyanide in combination with an inorganic water-soluble nickel or cobalt salt, such as sulfate, and nitric acid or phosphoric acid as an electrolyte. For most purposes, an alkali metal nitrate such as potassium nitrate is used in conjunction used with nitric acid. It has also been found that it is advantageous if the £ 5ad is a wetting agent or contains a surfactant such as an anionic fluorine-containing wetting agent. The concentration of the alloying elements is like this selected that the resulting coating contains less than about 1 wt% of the alloy metal.

The invention will now be described in more detail.

The aqueous galvanic daders according to the invention have one pH, which is above about 0.75 but below 2.75. It is it has been found that if the pH of the bath is not above 0.75, the properties of the coating change significantly and it is not possible to use the decoration

... / 15

• · η m 9 *

in the desired color when the pH-Vert des Bath is above 2.75, this has an unfavorable effect on the stability of the bath and the desired stable Au (III) bath cannot be sustained. It is therefore an essential feature of the invention that the galvanic baths a pH value above 0.75 »but not above 2.75 can be used.

As already described, another of the essential features of the invention consists in the use of a water-soluble gold complex or a water-soluble gold compound in which the gold ion is in a trivalent state as the gold source. The preferred source of gold is an alkali metal auricyanide and particularly preferred is potassium auricyanide. In general, the bath contains about 1 hour to 16 g / l, preferably 6 to 8 g / l, alkali metal auricyanide. In general, the salts of trivalent gold contain about 52 to 5% gold, preferably about 53 to 50% gold. It is important that the alkali metal auricyanide be substantially free of chlorine ions.

The alloying elements are inorganic salts of nickel, cobalt; Copper, indium, zinc, tin and the like. In the Galvanic baths according to the invention, the concentration of the alloy element salt is in the range of about 0.5 to about 10 g / l, preferably 1 to 5 g / l »

T) io bath or acid matrix used for the present purposes is preferred is sulfamic acid or citric acid. Anor-

BADiOBICatNAL ,,

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ganic acids such as phosphoric acid and sulfamic acid, and organic acids such as oxalic acid and Cxt.ronensa.ure can can also be used. The concentration of the acid matrix is in the range of about 10 to about 100 ml / l, preferably from about 20 to 70 ml / l.

The color of the gold plating that will be adhered to on a particular electroplating bath according to the invention can originally be determined by the particular alloying element and / or the acid matrix selected in the formulation of the bath. Once the color characteristics have generally been determined by the choice of components, the color of the gold coating produced is determined by the particular pH value within the specified range at which the bath is operated. For example, a particular electroplating bath formulated according to the invention, when operated at a pH of 1.5, can produce a gold coating the color of which is 2h K Old English. However, operating the same bath at a pH of 1.9, the color of the gold plating can be changed to 22K Hamilton. It should be noted that these designations do not indicate the purity of the gold coating obtained, but are equivalent color designations. Even if the process according to the invention can produce changes in the color equivalency designation of the resulting coating at different pH values, within the specified range, the purity remains

... / 17

BATH ORIGINAL

of the coating essentially unchanged; it is general in the range of about 22K to 2 ^ K (carats).

In carrying out the method according to the invention for producing different colored coatings, the change in the pH at which the bath is operated is effected simply by adding a suitable alkaline or acidic material to the bath. If an increase in pH is desired, this can be done by adding small amounts of alkaline material such as ammonium hydroxide, sodium hydroxide, potassium hydroxide and the like. If it is desired to lower the pH of the bath, this can be done by adding additional amounts of the acid matrix material to the bath. In general, the process can be carried out over a wide range of current densities. For example, current densities in the range of about 1.08 will be used to about 3.2J A / dm, preferably from about 1.61 to 2.15 A / dm.

In most cases, the electroplating bath is kept at a temperature of about ho to 60 ° C. The deposition time can vary widely, depending on factors such as the type of substrate, the required coating thickness, etc. As indicated above, the electroplating baths according to the invention can be used with benefit for electroplating in the jewelry and decoration sector. The substrates can be made from, for example, brass, copper, copper alloy, steel, stainless steel, and other common metals

... / 18

"BAET

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and be alloys.

In most cases, when carrying out the process according to the invention on an industrial scale, it is expedient to clean the substrate or pretreatment before it is subjected to electroplating. For example, a metal substrate such as a brass plate degreasing using a hot alkaline one Solution and then rinsed with deionized water. The plate can then be put in at an elevated temperature held hydrochloric acid or sulfuric acid can be immersed. Finally it can be rinsed again with deionized water. All of these and other pre-treatments and pre-cleaning treatments are known in the art and the actual process that is used is not Feature of the present invention.

In addition, with respect to wear-resistant coatings, as previously described, one of the essential features of this aspect of the invention is the use of a water-soluble gold complex or compound as the gold source in which the gold ion is trivalent. The preferred source of gold is an alkali metal auricyanide, and the particularly preferred gold salts contain about 52 to 5%, preferably about 53 to 5% gold metal. It is important that the alkali metal auricyanide be substantially free of chlorine ions. Typically wii -d it in the bathroom in quantities of

BATH ORIGINAL

about 4 to about λ6 g / l, preferably from about 6 to about 8 g / l, are used.

The alloy element coraponent is either an inorganic nickel or cobalt salt, such as nickel or cobalt sulfate, usually in the hydrate form. In the baths according to the invention, the nickel or cobalt salt is present in an amount of 1 to 8 g / l. In the preferred baths of the invention the cobalt sulfate is present in an amount of about 3 prior to h g / l, nickel sulfate in an amount of about 2 to 3 g / l · ^ he preferred electrolyte is either nitric acid or phosphoric acid. Nitric acid is used in concentrations in the range from about 30 to 60 ml / l, and phosphoric acid in concentrations from about 100 to 150 ml / l. If nitric acid is used, an alkali metal nitrate, for example potassium nitrate, is added to the bath as an electrolyte booster in quantities of up to 70 g / l.

In accordance with preferred features of the invention, small amounts of an anionic fluorine-containing surfactant such as a mixture of potassium perfluoroalkyl sulfonates (marketed under the tradenames FC-98 and FC-95 by the Minnesota Mining and Manufacturing Company) can be used to advantage . The amount of wetting agent or surfactant is generally in the range of about 2 to 10 ml / l, preferably from about 6 to about k "ml / l.

... / 20

BATH

- 2Ci - * * *

PC-95 and FC-98 are potassium perfluoroalkyl sulfonates, and theirs Use is generally preferred. Both wetting agents, FC-95 and FC-98, decompose at 39O ° C. A 0.1 $ aqueous FC-95 solution has a pH of 7 to 8, an O, aqueous solution FC-98 solution has a pH of 6 to 8. FC-98 has something lower surface activity and creates a foam that is less dense and less stable. Both types of wetting agent have excellent chemical and thermal stability, especially in acidic and oxidizing systems Preparation of these perfluoroalkyl sulfonates is disclosed in US Pat. No. 2,519,983, which discloses the use of such surfactants the area of electroplating is disclosed in US Pat. No. 2,750,330 described. The contents of these patents are here included by mentioning them.

Another essential feature of the invention is that the pH of the bath is maintained so that it the Does not exceed a value of about 0.75. It has been found that where the pH exceeds 0.75, the Ductility of the coating decreases, resulting in deterioration the wear resistance results. Although the reasons for this have not yet been fully clarified, it is assumed that organic materials from the bath at the higher pH values deposited with the gold, causing deterioration caused in ductility.

... / 21

BATH ORIGINAL

* * * · Ml »(1 t at

The pH of the electroplating bath is typically in the range from about 0.1 to 0.5, preferably from about 0.3 to 0. h.

In most cases, the galvanic baths according to the invention are kept at a temperature of about 45 to 60 ° C, and current densities from about 0.05 to 0.65 A / dm, preferably 0.1 to -0.5 ^ A / dm applied. "The separation times can vary widely depending on factors such as the type of substrate, the desired thickness of the coating, and the like. As noted earlier, the galvanic baths according to the invention can be used both in the field of Electronics as well as in the jewelry and decoration sector can be used with success. Examples of suitable substrates include: brass, copper, copper alloys, stainless Steel, steels and other common metals and alloys.

In most cases, when carrying out the process according to the invention on an industrial scale, it is expedient to clean or clean the substrate pretreatment before it is subjected to electroplating. For example, a metal substrate such as a brass plate can be degreased using a hot alkaline Solution and then rinsed with deionized water. The plate can then be put in at an elevated temperature held hydrochloric acid or sulfuric acid can be immersed. Finally, it can be rinsed again with deionized water will. All of these and other pre-treatments and pre-cleaning treatments are common in the relevant technology and that

... / 22 ORIGINAL BATHROOM

certain procedures employed do not form part of the present invention.

It will be apparent to those skilled in the art that the electroplating process and the facility used in the practical implementation; of the invention with regard to the substrate to be treated and the desired results can be greatly modified »

The invention will now be further exemplified by way of the following Embodiments and Tables I and II explained in more detail.

Example I.

An electroplating bath was made from the following components:

Ingredients g / l

Potassium auricyanide 8

Nickel sulfate 2.5

Sulfamic acid 30

Water rest

The bath had a pH of 1.5. A brass plate was placed under vigorous stirring of the bath at 50 ° C. _for a current density of 2.15 A / dm '"and a deposition rate of 0.0025 mm / 8 min. electroplated. A glossy coating of gold color ZkK yellow was obtained,

... / 23

ΒΔΠ ORIRIMAJ

Example TT

It wxirclo oin /: i \ lvnniochos bath from those listed below

Share hor ^ oatollt:

Beatnndtoilo

Potassium nuricy * \ n id °

NiCkGlSUlTat ² »5

SuIf amins tiuro 30

Ammonium hydroxide ¹ ^ ml / l

Water rest

This bath had a pH of 2.2. A brass plate was electroplated therein with vigorous stirring at 50 ° C., a current density of 2.15 A / dm ² and a deposition rate of 0.0025 mm / 8 min. The deposited alloy had the gold color i'iIC Hamilton.

Example III

Another bath was made from those listed below

Components manufactured:

Ingredients g / l

JCalium auricyanide 8

Nickel sulfate 2.5

Citric acid 60

Water rest

BATH ORIGINAL

- zh - ■

The pH of this bath was 2.2. In it was a «

with vigorous stirring at 50 ° C. and a current density of 2.15

A / dm electroplated. The deposited alloy had

the gold color 14K green.

Example IV

Five gold alloy baths were prepared to demonstrate the invention. Bath A is a state-of-the-art Au (l) -Co bath. It was prepared by adding potassium citrate to 500 ^m l of deionized water, after which the salt of the alloying element was added. To the resulting solution, 100 ml of a solution containing Au () in the predetermined amount was added. Citric acid was then added and the volume made up to one liter. The pH value was adjusted with the appropriate salts: potassium nitrate to increase the pH value and citric acid to lower it.

The four other gold alloy plating baths B, C, D and E concluded the use of Au (IIl) - and two different ones Matrices, Nitrate 'and Phosphate, a «The Composition of the Baths A and baths B to E are listed in Table I. Baths B through E were made by adding the metal salts about 800 ml of deionized water were added, after which was acidified, added the wetting agent and made up to one liter with deionized water.

A number of tests were carried out to determine the effect of the

... / 25 ORIGINAL BATHROOM

9 * ♦ ·

different concentrations of Au (IIl) -, alloy elemont salt and electrolyte salt, the temperature, the pH word, the specific gravity and the current density in two different Determine matrices.

All test work was carried out on a 1 liter scale. The anodes were made of 4 x 10 cm platinum-coated titanium wire mesh. The bath was moved by means of a magnetic stirrer. The galvanic

Deposition was carried out on pre-cleaned brass plates

Surface area of approximately 13 »1 cm was made. The actual Surface area was determined from the weight and the known density of brass, which is 8.5 g / cm. Depending on the current density, the electroplating time * was in the range from 5 to 20 minutes. Longer plating times were used for thick coatings required for analytical testing.

The operating conditions used for each of the baths can also be found in Table I.

The chemical, physical and mechanical properties the coatings were determined and the results are shown in Table II.

.. * / 26

BATH ORIGINAL

DO>

ro

TABLE I.

A B _C D E

Bath composition Autronex CI Au-Ni (HNO) Au-Co (HNO) Au-Nz (H-POk) Au-Co (H-POr)

Au as K (Au (CN) ₄ ) g / l 8 8 6 6

Au as K (Au (CN) ₂ ) g / l 8

Co as CoSO,, 7H ₂ O g / l
(21.0% Co) 0.1 - • 40 t 50 1 - Ni as NiSO..6H ₅ O g / l - 1 - ■ 0.35 - 0.5 KNO ₃ g / l 70 1.048 70 FC-98 ml / l 5 0.48 5 5 H PO ₄ ($ 85) ml / l 2.5-2.7 - 120 HN0 "(7O-7ΐ £) ml / l
3 0.30-0.35 40 - Citric acid 50 - - Potassium citrate 70 - - Operating conditions Temperature C 33 50 50 PH value 4.0 0.35 0.5 Specific weight g / cm 1.075 1.048 1.090 Current density 0, 12 0.48 0, 16 Cell voltage 4.0-4.5 2.5-2.7 2.3-2.4 Conductivity, m JX. 0.04 0.30-0.35 0.10-0.13

5 «120

C # * C

50

0.5

1.090

0.16c 2.3-2.4 0.10-0.13 c

Properties of the coating

Alloy element content, wt. Carbon content, wt .- ^ Wear resistance, cycles heat stability

Contact resistance, m internal stress ductility hardness

₂ density g / cm

Corrosion resistance pores / cm ² at 4θ / <tension s ρ annung

TABLE II B.
Auri-Ni
(ENT ₃ ) C.
Auri-Ni D.
Auri-Co E.
Auri-Co
f Τ.Τ Ό Γ \ ι
1 Xi 4-1 Sr \ J f j A.
Autronex CI
(Au-Co) 0.5 o, 9 0.3 0.3 - # 0.2 0.05 0.05 0.05 0.05 0.2 4000 4000 4000 4ooo 2000 - no
0.45 modification
0.45 at 250 ^O C
0.3 -8h-
0.3 I.
Eruptions
at 175 ° C-10
min.
0.6 -58 -55 -55 -190 +240 Well Well Well Well very brittle 2IO-23O 230-250 210-230 2IO-23O 170 19.1-
19.2 19.1-
19.2 19.1-
19.2 19.1-
19.2 17.3-
17.5 5 8th 5 3 10 290 280 300 300 too brittle

co

Many of the differences between the coatings obtained from the Au (III) complex-containing solutions and the Au (I) system show the superiority of the alloys according to the invention with regard to the chemical composition of the alloys it should be noted that the "carbon content of the coatings obtained from Au (III) alloy baths is below the detection limit of the Auger analysis was. The influence of the reduced carbon content was increased Heat stability, reduced contact resistance, increased Ductility and possibly in the nature of internal stresses, none occurred during terapping at 2 ^ 0 C for 8 hours Blistering or eruption on the coating surface. The internal compressive stress contributes to the increased ductility. Thicker coatings show no signs of cracking, the usually for coatings obtained from Au (I) -containing baths occur with their internal tensions.

The greater wear resistance is a function of several Factors. With such a low carbon content, it has to Hardening originate from the alloy element gGha.lt. The hardness, which is a measure of the resistance to deformation, shows that the plastic flow would have to be reduced and the wear resistance is improved. The slightly better ductility in on the order of $ 1, and the elongation also increases the Material resistance to wear. The wear resistance results show a significant improvement over

... / 29

ORlRlNAJ

the results obtained on coatings made from an Au (l) -half Bath were obtained. With advance payment; of the crosshair wear test device and a load of 200 g, both coatings obtained from the Au (III) bath withstood up to 1000 passes 1.91 to 2.03 µm thick.

The many physical and mechanical property improvements which are the alloys which are made up of the auricyanide complex containing solution have been obtained are of quite considerable benefit. The main advantages of the Au (IIl) system compared to the Au (i) system are the following:

a) improved wear resistance compared to Au (l) baths that contain organic acids, while * a comparatively high degree of ductility and hardness is maintained;

b) lower contact resistance; and

c) lower co-deposition of carbon;

For the person skilled in the art, it follows from the description that still numerous modifications and changes to the specified preferred Aixsführungs forms are possible without thereby the scope of the invention is left.

BATH ORIGINAL

Claims (1)

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HAUCK, SCHMITZ ^ * G ^ AAI ^! O "* \ VRHWKRT, DÖRING HAMDlJRO MUNICH DÜSSELDORF PATENT ADVOCATE. NBUER Al . 2000 HA MUUHO OMI International Corp. 2i44i Hoover Road ¥ arren, me. 48089 United States Dlpl.-Phys. W. SCHMiTZ - Dipl.-Ing. B. GRAALFS Neuer Wall 41 · 200O Hamburg Telephone + Telecopier (04O) 86 67 SB Telex 0211769 Input d DlpL-Ing. H. HATJCK - DipUng. W.WBHNERT Mossnrtstrnßo 23 8000 Munich Telephone + Telecopier (Ü89) 50 02 36 Telex 05 216 503 unmu d Or.-In «. W. DORING K.-Wilhelm-Ring 414000 Düsseldorf Telephone (02 11) 57 50 27 ZUSTBLLUNCSANSCHRIFT / PLEASB REPLY ΎΟ: , December 29, 1983 Bath for the galvanic deposition of a 'wear-resistant gold alloy and process for the deposition of a wear-resistant gold alloy using this bath Expectations : 1.) Aqueous bath for the galvanic deposition of a gold alloy improved wear resistance on substrates, characterized in that it has a pH that is above 0.75, but does not exceed 2.75, and an alkali metal auz'icyanid complex, a water-soluble salt of an alloy element and an acid atrix from the group Oxalic acid, citric acid, sulfaniinsätire, phosphoric acid, Contains nitric acid and hydrochloric acid. Buropoan Ptuont Attorneys Zusplnseono Representative at the EuropÖlacheii Patent Office Deutsche Bank AO Ilnmburg, No. 05/28 497 (BLZ SOO 700 OC) Postochock Hamburg 2842-200 Dvcadner Dank AO Ilmnbiii · ;;, No. tKVIfJOHf * (ΙΜ / Λ 200 SOO 00) 2, bath according to claim 1, characterized in that it is as Alkali metal auricyanide complex contains potassium auricyanide. 3. Bath according to claim 1, characterized in that the content of the alkali metal auricyanide complex of metallic gold is in the range of about 52 to 5k wt .- ^, k. Bath according to Claim 1, characterized in that it contains a metal from the group consisting of nickel, cobalt, copper, indium, zinc and tin as the alloying element. 5 «bath according to claim 1, characterized in that the water-soluble Salt of the alloying element is nickel sulfate. 6. Bath according to one of claims 1 to k, characterized in that the water-soluble salt of an alloying element is cobalt sulfate, 7. Bath according to claim 1, characterized in that it contains sulfamic acid as the acid matrix. 8. Bath according to claim 1, characterized in that it is as Acid matrix contains citric acid. 9. A method for the electrodeposition of a gold alloy from a bath which is an aqueous solution containing an alkali metal gold cyanide complex and an alloying element, RAH ORIGINAL characterized in that the bath of claim used and galvanic deposition while maintaining the pH of the bath at a certain value • within the specified range makes a gold alloy plating of a specific desired color to obtain. 10. The method according to claim 9 »characterized in that potassium auricyanide is used as the alkali metal auricyanide. 11. The method according to claim 9 »characterized in that a metal from the group nickel, Cobalt, indium, copper, zinc and tin are used. 12. The method according to claim 11, characterized in that is called the water-soluble salt of the alloying element Nickel sulphate is used. 13 · Method according to claim 11, characterized in that is used as the water-soluble salt of the alloying element cobalt-bilfate. Ik, method according to claim 9, characterized in that the acid matrix used is sulfamic acid. 15. The method according to claim 9, characterized in that Citric acid is used as the acid matrix. BATH ORIGINAL 16. Aqueous bath for the electrodeposition of a wear-resistant binary gold alloy on substrates, the gold alloy being less than about 1 wt .- ^ cobalt or Contains nickel as an alloying element, characterized in that that the bath has a pH that is not above 0.75, and an alkali metal auricyanide Icomplex, a water-soluble one Contains nickel or cobalt salt and nitric acid or phosphoric acid as acidic electrolytes. 17. Bath according to claim 16, characterized in that it is as Allcalimetal auricyanide complex contains potassium auricyanide. 18. Bath according to claim 16, characterized in that the content of the allcalimetal auricyanide complex of metallic gold is in the range from about 52 to $ h wt .- ^. 19. Bath according to claim 16, characterized in that it is the contains water-soluble cobalt or nickel salt in an amount ranging from about 1 to 8 g / l. 20. Bath according to claim 19 »characterized in that it contains nickel sulfate as the water-soluble nickel salt. 21. Bath according to claim 19f, characterized in that it is as contains water-soluble cobalt salt ICobalt sulfate. 22. Bath according to claim 16, characterized in that it is as acidic electrolytes containing nitric acid. ... / 5 ORIGINAL BATHROOM. 23 · bathroom. after. Claim. 22, characterized in that it is additionally Contains potassium nitrate. Zh, bath according to claim 16, characterized in that it contains phosphoric acid as the acidic electrolyte, 25. Bath according to claim 16, characterized in that it is additionally contains a small amount of wetting agent. 26. Process for the electrodeposition of a gold-cobaltor Gold-nickel alloy from a bath containing an aqueous solution of an alkali metal gold cyanide complex and a Contains cobalt or a nickel salt ", characterized in that the bath of claim 16 is used as the galvanic bath. 27. The method according to claim 26, characterized in that a bath is used, which as an alkali metal auricyanidkomplex Contains potassium auricyanide. 28. The method according to claim 26, characterized in that a bath is used which contains nickel sulfate as a water-soluble nickel salt. 29. The method according to claim 26, characterized in that a bath is used as the water-soluble cobalt salt BATH ORIGINAL " 6 «· · ·» W * for 1 » Contains cobalt sulphate. 30. The method according to claim 26, characterized in that a bath is used whose acidic electrolyte is nitric acid, 31. The method according to claim 30t, characterized in that one uses a bath that also contains potassium nitrate. 32. The method according to claim 26, characterized in that one a galvanic bath is used, the acidic electrolyte of which is phosphoric acid, 33. The method according to claim 26, characterized in that a bath is used that also contains a small amount of wetting agent. RAH ORIRIMÄJ