DE2226699A1 - Electroplating bath for the deposition of rhodium-platinum alloys - Google Patents

Description

of rhodium-platinum alloys

The invention relates to an electroplating bath for .the rebound of rhodium-platinum alloys.

Electroplated rhodium deposits are used as a decorative coating and, because of their extraordinary hardness and resistance to corrosion and wear, as contact base metal. Rhodium coatings are particularly useful as a protective layer for silverware, deep dishes, jewelry, and electronic products. However, such coatings, in particular thick ones, tend to be brittle.

Electroplating of platinum is not so popular in jewelry and decorative coatings like rhodium precipitates as their color is darker than rhodium or silver and tends to deteriorate over time to darken. There is a strong interest in the achievability of shiny, low-stress deposits of rhodium, platinum or leather

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alloys of these two metals.

It is an object of the invention to provide a new rhodium-platinum electroplating bath indicate that it produces shinier precipitates than it does from a bath with either of the two Metals alone are obtainable.

Another object of the invention is to provide a new method for obtaining brighter galvanic rhodium-platinum deposits to be provided.

A more specific object of the invention is to provide a new electroplating bath that has a ductile, low stress, generated mirror-like rhodium-platinum precipitate, as well as to indicate an electroplated object that has a ductile, low-stress, mirror-like rhodium-platinum precipitate.

Further objects and advantages of the invention will be apparent from the following description.

Although sulfamic acid Pt (NH ^) ₂ (N0 ₂ ) ₂ baths produce silky shiny or semi-bright galvanic deposits, it was unexpectedly found that when Pt (NH ^) ₂ (N0 ₂ ) ₂ (also platinum-P-salt called), rhodium sulfate, phosphate or sulfamate and sulfaminosulfuric acid are used for electroplating, a rhodium-platinum precipitate of improved gloss is obtained. If, in particular, rhodium is the predominant metal in the bath, the precipitate obtained is as bright as a mirror.

In the practice of the invention, are platinum P salt and Sulfaminschwefelsäure mixed with a sufficient amount of water rhodium sulfate, to obtain the following approximate concentrations:

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Rhodium metal (in the form of sulfate,

Phosphate or sulfamate) 0.1-15 g / l

Platinum metal (in the form of platinum-P-

SaIz)

0.04 - 24.0 g / l

Sulphamic acid 20 g / l - saturation concentra tion

Preferably the rhodium metal concentration ranges from about 0.5 to 12 g / l, in particular from about 2 to 10 g / l. Preferably the platinum metal varies from about 0.07 to 12 g / l, in particular from about 0.1 to 10 g / l .. The sulfamine sulfuric acid concentration varies from 30 g / l to the saturation concentration, in particular from 50 to 100 g / l.

A bath rich in rhodium is used for the galvanic Precipitation of a predominantly rhodium-containing alloy used. In this bath, which contains a lot of rhodium, is enough the rhodium metal concentration generally from about 1 to 12 g / l, preferably from about 2 to 7 g / l; the platinum metal concentration varies from about 0.04 to 1.2 g / l., preferably from about 0.1 to 0.7 g / l and the sulfamine sulfur elic acid concentration varies from about 30 g / l to the saturation concentration, preferably from 50 to 100 g / l, The rhodium concentrations for the bath with a high concentration of rhodium can be further subdivided depending on the desired Precipitation thickness. For precipitates up to 51 µm (2 microinches) thick, it is preferred that the rhodium content of the bath is 1-2 g / l; for precipitation from 51 to 254 / µm (2 to 10 microinches) is the rhodium content preferably 2-5 g / l; and for precipitates thicker than 254 / µm (10 microinches) the rhodium content is preferably 2-10 g / l. The platinum content varies for everyone Thickness range proportional to the rhodium content.

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2226693

A high platinum bath is used for electroplating with an alloy predominantly containing platinum. In this high platinum bath, the platinum metal concentration varies from about 2 to 24 g / l, preferably from about 5 to 12 g / l; the rhodium metal concentration varies from about 0.10 to 5 g / l> preferably from about 0.2 to 2 g / l j and the sulfaminosulfuric acid concentration varies from about 30 g / l to saturation, preferably from about 50 to 100 g / l.

In all of the baths mentioned above, the limits of the current density can usually be increased by adding concentrated sulfuric acid generally to about 100 ml / l of the solution, preferably from 1 to 50 ml / l of the solution.

The electroplating solution according to the invention can be coated any substrate suitable for receiving an electroplating can be used, in particular such base metals as copper, brass, nickel, soft iron, silver and the like Dissolution of the base metal could result in contaminating the bath, it is preferable that the base metal be protected is, e.g. by coating by means of electrical short-term coating with palladium, palladium-gold or preferably gold, so that attacking the base metal is prevented. If the base metal contains iron, it is preferred to use the base metal first to be pre-plated with e.g. nickel, copper or Silver before the short-term plating takes place. The rhodium-platinum alloy can be removed from the electroplating bath at a temperature from about 15 to 83 ° C can be precipitated in that a current with a current density of about 0.015 to 0.12 A / cm (5 to 40 ASF) is sent through the bath to the cathode immersed in it. Preferably the current density is

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about 0.03 to 0.09 A / cm ² (10 to 30 ASF) and the temperature about 36 to 55 ° C. The lower temperatures are generally used for rapid precipitation and the higher temperatures are generally used for heavier precipitation and high platinum precipitation.

The precipitate obtained using a high platinum bath contains about 90 to 99% platinum, preferably from about 93 to 98 weight percent. The high rhodium-containing bath results in a low-tension one, predominantly rhodium containing precipitate which is mirror-like and ductile and contains from about 90 to 99.5% rhodium, preferably from about 93 to 99% rhodium, in particular from about 96 to 98.5% by weight rhodium and from about 6.5 to 10% platinum, preferably from about 1.0 to 7% platinum, in particular from about 1.5 to 4.0% by weight platinum.

The precipitates obtained by the method according to the invention range from short-term coatings, e.g. 0.5 / µm (2 microinches) to thick coatings of 5.08 / µm (200 microinches) or more thickness. Preferably the method is used to produce low stress deposits from 1.27 to 3.87 / µm (50 to 150 microinches).

The addition of trace amounts of lead to the high rhodium bath according to the invention increases the life of the Bades in terms of mirror-like precipitation. In general, up to 10 mg of lead metal per liter of bath liquid added, preferably from 2 to 6 mg / l. The lead is added as a water-soluble salt, preferably as lead nitrate .

L) = xr> Ei bark rhudium-containing bath is particularly useful for dixB !, Lektropiabieren of coins, jewelry, hollow vessel

^Ί 'ι ⁽ ] R f "! / Lf) f] / ·

sen, tableware and the like and gives a mirror-like sheen, which contributes greatly to their appearance. That Highly rhodium-containing bath is particularly useful for electroplating silver objects, preferably of those containing more than 90% by weight of silver, insofar the precipitate the tarnishing of the silver, probably because of the pore-free nature of the precipitate, prevented. When electroplating silver objects with the high rhodium-containing bath, the objects preferably first given a short-term coating of gold.

The invention is further illustrated by the following examples:

example 1

Bath volume 1 liter:

Rhodium metal 2g (as sulfate,

Phosphate or sulfamate)

Platinum metal, 0.05 g (as PIa-

tin-P salt)

Sulfamine sulfuric acid 30 g

Sulfuric acid 5 ml concentrated

Cathode power:

with stirring 12 mg / A min

without stirring 6-9 mg / A min

The test plates had a brass-gold short-term coating

Mistake. Mirror-like corsetry was at 0.015 A / cm (15 AÜfc ¹ ) - 0.0217 A / cm * "(20 ASF) and 43-49 ° C without stirring

obtain.

η η ^r : ι / ι

- V _

With stirring at 0.015-0.022 A / cm ² (15-20 ASF) and 43-49 C, bright precipitates were obtained throughout, with the exception of a slight veiling on the edges of the plates, which had higher current densities.

When the platinum metal content was increased to 0.12 g / l, the result was mirror-like precipitates when stirred and the slight obscuration was avoided at 0.015 A / cm (15 ASF). However, slight fogging occurs at 0.022 A / cm ² (20 ASF) at the edges of the test panel.

The test plate was set to 2.54 / µm (100 microinches) Thick plated with stirring, and the analysis showed that the precipitate contains 2-5% platinum and is low in tension.

Various items have been electroplated with similar success in the aforementioned bathrooms, including nail clippers, Tie pins, rings and salad forks.

Example 2

Rh metal 2 g / l (as sulfate, phosphate

or SuIfamat)

Pt-metal 0.2 g / l (as P-salt)

Sulphamic acid 90 g / l

Operating conditions:

Temperature 40 - 48 ⁰ C

No bath movement

Current density 0.016 A / cm ² (15 ASF) maximum

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Trial Plates: Bare nickel-plated brass with thin
Gold plating.

Participation results:

The test plates were plated mirror-like [

(0.016 A / cm ² (15 ASF)) with a surface finish \

whose color is that of a highly polished piece of silver ^;

approaching. - - 0.5 to 5 min .:

Thickness: 0.254 µm (10 microinches) short term coating. '/

Other objects coated with a mirror-like finish in the above bath are: ' /

Nail clippers bare nickel + thin gold over- ■

train ι

Coins (silver with a thin gold coating j

nes palladium and short-term gold plating '

2 '

Candlelabrum ... total area 0.186 m

(2 square feet) bare nickel,

plated + short-term gold plating.

Example 3

Rhodium metal 5 g / l I.

Platinum metal 0.5 g / l

Sulphamic acid 90 g / l

Sulfuric acid 5 ml / 1

Objects plated with this bath:

a) Brass watch glass bezels are at 48 to 50

r \

and 0.022 A / cm ² (20 ASF) plated for 20-42 minutes. Mirror-like, silver-colored precipitates are obtained, the thicknesses of 2.54 - 5.08 yum (100 - 200 microns)

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croinches).

b) 2-14 K gold rings are ² (20 ASF) plated at 46 ⁰ C and 0.022 A / cm 5 min without agitation. Precipitates were obtained 0.25-0.39 yum (10 15 microinches) thick, mirror-finished and silver in color.

c) test plate nickel-plated brass with a thin gold coating is carried out at 43 - 46 ⁰ C and plated 0,022 A / cm (20 ASF) with agitation for 10 minutes. The precipitate is 1.27-1.78 / µm (50-70 microinches) thick, mirror-like and low-tension, and is silver in color.

Example 4

Rhodium metal .......... 2 g / l (as sulfate, phosphate

or SuIfamat)

Platinum metal 0.2 g / l (as P-salt)

Sulphamine sulfuric acid ... 90 g / l

Sulfuric acid 5 ml / 1 (concentrated HpSO,)

Distilled water ... according to volume

a) A test plate made of nickel-plated brass with a thin gold coating was at 43-46 ⁰ C and

0.022 A / cm (20 ASF) plated for 2 minutes with no bath agitation. A 0.05 / µm (2 microinches) thicker, mirror-finish Precipitation of silver paint is obtained.

b) A test plate made of nickel-plated brass with a thin gold coating was at 46 ⁰ C and θ, 022 A / cm

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(20 ASF) plated for 10 min with bath agitation. A mirror-like precipitate of .1.02 - 1.27 / um (40-50 microinches) is obtained.

c) sterling silver coins are being provided with thin gold coating and then 2 min at 43 - / cm ² (20 ASF) plated 46 ⁰ C and 0.022 A without agitation. Mirror-like precipitates of 0.077-0.127 µm (3-5 microinches) were obtained.

Example 5

Rhodium metal 2 g / l (as sulfate, phosphate

or SuIfamat)

Platinum metal 12 g / l (as P-salt)

Sulphamine sulfuric acid ... 100 g / l

Distilled water ... according to volume

A test plate made of nickel-plated brass with a thin gold coating was ^{plated with bath agitation at 65-80 ° C. and 0.022 A / cm 2} (20 ASF) for 17 minutes. A 2.5 µm (100 microinches) thick, mirror-like precipitate was obtained.

Claims - 11 -

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Claims (18)

Patent claims: 1. Electroplating bath for the precipitation of a rhodium-platinum alloy, marked
by an aqueous solution of Rhodium metal (in the form of sulfate, phosphate or
• sulfamate) 0.1 to 15 g / l Platinum metal (in the form of the P-salt) 0.04 to 24 g / l Sulphine sulfuric acid 20 g / l - saturation concentration tion 2. Bath according to claim 1, characterized
by an aqueous solution of: Rhodium metal (in the form of sulfate, phosphate or Sulfamate) 0.5 to 12 g / l Platinum metal (in the form of the salt) 0.07 to 12 g / l Sulfamic acid 30 g / l - saturation concentration tion 3. Bath according to claim 2, characterized in that it is up to about 100 ml / l
contains concentrated sulfuric acid per liter of the solution. 4. Electroplating bath for the precipitation of a predominantly rhodium-containing alloy, marked by the aqueous solution of: Rhodium metal (in the form of sulfate, phosphate or Sulfamate) ₀ "1 to 12 g / l Platinum metal (in the form of the P-salt), 0.04 to 1.2 g / l SuIf amine sulfuric acid _c . 20 g / l - satiety concentration 209853/1004 "~ 5. Bath according to claim 4, characterized by an aqueous solution of: Rhodium metal (in the form of sulfate, phosphate or SuIfamats) 2 to 7 g / l Platinum metal (in the form of the P-salt) 0.1 to 0.7 g / l Sulphamine sulfuric acid 30 g / l - saturation conc tion 6. Bath according to claim 5, characterized in that that the concentration of sulfamic acid is 50 to 100 g / l. 7. Bath according to claim 5, characterized in that it is additionally up to about 100 ml / l concentrated sulfuric acid per liter of the solution contains. 8. Bath according to claim 6, characterized in that it is additionally up to about 100 ml / 1 concentrated sulfuric acid per liter of the solution contains. 9. Bath according to claim 6, characterized in that there are additional trace amounts of lead in solution. 10. A method for applying a rhodium-platinum alloy by electroplating, characterized in that that the rhodium and platinum from the aqueous bath according to claim 1 on a base metal are deposited galvanically. 11. Process for applying a predominantly rhodium-containing - 13 -209853/1004 tend alloy by electroplating, thereby characterized in that the rhodium and the platinum from a bath according to claim 4 on a base metal are deposited galvanically. 12. A method of electroplating an alloy predominantly containing rhodium, thereby characterized in that rhodium and platinum from the bath according to claim 5 on a base metal are deposited galvanically. 13. Method for applying a predominantly rhodium-containing Alloy by electroplating, thereby characterized in that rhodium and platinum from the bath according to claim 8 on a base metal are deposited galvanically. 14. Article provided with an electroplating, characterized by a base metal and a ductile, mirror-finish, essentially stress-free, electroplated electroplating layer made of a rhodium-platinum alloy containing about 90 to 99.5 % by weight of rhodium and about Contains 0.5 to 10% by weight of platinum. 15. The object provided with an electrical plating according to claim 14, characterized in that the electroplated layer contains from about 96 to 98.5% by weight of rhodium and from about 1.5 to 4% by weight of platinum. 16. The object provided with an electroplating according to claim 15, characterized in that that the base metal is at least about Contains 90 wt% silver. : - 14 - 209853/1004 17. The object provided with an electroplating according to claim 16, characterized in that that it contains a temporary coating of gold between the base metal and the alloy layer. 18. Electroplating bath for depositing a rhodium-platinum alloy, characterized by an aqueous solution of rhodium metal in the form of sulfate, phosphate or sulfamate, of platinum metal in the form of the P salt and sulfamic acid. Wb / Pe - 25 007 209853/1004