ITFI20130057A1 - SOLUTION FOR THE ELECTRODEPTITION OF A GOLDEN LEAGUE AND THE LEAGUE THEREOF DERIVING. - Google Patents

Description

PATENT APPLICATION FOR INDUSTRIAL INVENTION WITH THE TITLE:

SOLUTION FOR THE ELECTRODEPOSITION OF A GOLD ALLOY AND THE ALLOY RESULTING FROM IT FIELD OF THE INVENTION

The present invention refers to the field of solutions for electrodeposition of metal alloys and deriving alloys; in particular it refers to a solution for the electrodeposition of a gold alloy and the resulting alloy having color coordinates defined in the interval (L: 65-75; a: 6â € "9; b: 10-20 ).

STATE OF THE ART

The metal alloys obtained by electrodeposition are widely used in various production fields, both for their physical qualities and for their particular aesthetic aspect.

For this last purpose colored alloys are of interest, obtained through the electrodeposition of both single and alloyed metals; these alloys find practical applications in various fields: furniture, clothing, jewelery, and in general in all sectors that require objects with certain aesthetic characteristics.

The colored gold alloys are among the most used as they allow to obtain a wide range of colors and shades depending on the formulation used and the working conditions applied to obtain them.

Today it is possible to obtain the entire range of colors and shades of white, yellow, pink and even green with galvanic gilding baths; on the other hand, shades of brown and brown are difficult to obtain under simple conditions, and with chemically stable solutions.

It is therefore interesting to formulate chemically stable galvanic baths, easy to conduct and maintain, usable for the electrodeposition of brown gold alloys with color coordinates included in the range: (L: 65-75; a: 6â € “9; b: 10-20) that have a lucid and coherent deposit.

SUMMARY OF THE INVENTION

The present invention solves the above problems by means of an aqueous solution for electrodeposition of a gold alloy; said solution comprising a salt of Gold (Au), a salt of Iron (Fe) and a salt of Vanadium (V), and optionally one or more salts of other metals suitably chosen from the salts of Cobalt (Co), Palladium (Pd ), Ruthenium (Ru), to modulate the shades of the final color; and also optionally comprising small quantities of one or more salts of Tellurium (Te), Gallium (Ga) or Bismuth (Bi), acting as brighteners and grain refiners.

The alloy resulting from the above solution has color coordinates in the range: (L: 65-75; a: 6â € “9; b: 10-20).

The object of the present invention is also a gold alloy, having color coordinates in the range: (L: 65-75; a: 6â € "9; b: 10-20), said alloy, obtainable from the above solution , having the following weight percentage composition:

∠’Au 86-91%;

∠’Fe 6-8%

∠’V 4-6%

- Co, Pd, Ru or their mixtures 0-0.5% Te, Ga, Bi or their mixtures do not enter the alloy, but have the sole function

rinse aid.

The subject of the invention is also a method for the electrodeposition of a gold alloy as described above by using the above solution.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, an electrodeposition solution is a galvanic bath and the solvent used is water.

The solution preferably contains a suitable buffer system, one or more complexing agents which, in addition to modulating the trend of the alloying metals, guarantee their stability in solution, and a surfactant agent which also acts as a rinse aid.

The salt of Gold can be Gold Chloride, Gold Sulfite, Potassium Dicyanoaurate, Potassium Tetracyanoaurate, Ammonium Cyanoaurate, or a combination of these.

Preferably the concentration of Gold as a metal ranges from 0.5 to 3 g / L, more preferably between 0.7 and 1.8 g / L, each time choosing the most suitable concentration to obtain the desired color coordinate triplet. included in the range of interest (L: 65-75; a: 6â € “9; b: 10-20).

The metals that are alloyed with Gold are mainly Iron and Vanadium, introduced into the solution in the form of their most common salts, such as for Iron for example - but not only - Iron sulphate, Iron carbonate, Iron acetate , Iron citrate and Iron chloride, depending on the chosen buffer system and the stability of the salt chosen in the solution environment, and for Vanadium, for example - but not only - Vanadium Oxychloride, Vanadium Oxytriethoxide, Vanadium Oxyripropoxide, Vanadium Oxyfluoride, Vanadium Oxide, Sodium Vanadium Oxide, Vanadium Halide.

The concentrations of the aforementioned metals range from 0.2 g / L to 1 g / L, each time choosing the most suitable concentration of each of them to obtain the desired color coordinate triplet within the range of interest (L: 65-75; a: 6â € “9; b: 10-20).

These metals are used in such a way as to obtain a lowering of the values of the color coordinates a and b compared to the typical values of a 24 kt gold deposit (L = 84-85; a = 6-8; b = 30-31); the quantities dosed for each single metal give a corresponding effect on these coordinates in relation to the concentration.

The other metals that can be introduced as salts in solution to modulate the color shades are Cobalt, Palladium, Ruthenium and their mixtures, also introduced in the solution in the form of their most common salts, such as - but not only - sulphate, carbonate, acetate, citrate and chloride, depending on the buffer system chosen and the stability of the salt chosen in the solution environment.

The concentrations of each of these metals range from 0.005 to 0.5 g / L, each time choosing the most suitable concentration of each of them to obtain the desired color coordinate triplet within the range of interest (L: 65 -75; a: 6â € “9; b: 10-20).

These metals are used in order to obtain a modulation of the values of the color coordinates L, a and b with respect to the typical values of a 24 kt Gold deposit (L = 84-85; a = 6-8; b = 30-31); the quantities dosed for each single metal give a corresponding effect on these coordinates in relation to the concentration.

In particular, we found that:

- Ruthenium causes a lowering of the L coordinate;

- Palladium and Cobalt cause an increase in the L coordinate;

We have also found that Tellurium, Gallium and Bismuth or their combinations improve the homogeneity of the color of the deposit and refine the grain of the deposit: they are introduced into the solution in the form of their soluble salts or their complexes stable in the working conditions of the solution, in quantities in the range 0.005 - 0.015 g / L as metal, for each of them.

The pH of the solution is not a critical parameter except for the stability of the chosen metals in solution and can be between 7 and 10, more preferably between 7.5 and 9.5, and is adjusted with sodium or potassium hydroxides, or with inorganic acids such as, but not limited to, sulfuric acid, phosphoric acid, formic acid.

In the working conditions the pH is kept stable through a buffer system chosen from the acid / salt pairs of acids such as gluconic, oxalic, citric, tartaric, malonic, malic, phosphoric, sulphamic, and others, which in addition to guaranteeing the stability of the pH also act as complexing agents towards the metals in solution, favoring their stability.

The salts of the aforesaid acids can be of sodium or potassium or of other alkaline and alkaline-earth metals which are soluble under the conditions of the solution.

The concentration of acids and their salts ranges from 30 g / L to 170 g / L, more appropriately from 50 g / L to 130 g / L.

It is also advisable to introduce one or more complexing agents into the solution, in concentrations between 20 and 50 g / L, such as for example ethylenediaminetetraacetic acid, ethydronic acid, nitrilotriacetic acid, ethylenediamino tetra methylenephosphonic acid, nitrilotrismethylenediphosphonic acid, in the form of free acid or in the form of salt.

The choice of the form of the complexing agent, of the concentration and of the composition of the possible mixture is determined by the color coordinates included in the range of interest (L: 65-75; a: 6â € "9; b: 10-20) which is they want to get.

The surfactant agent is selected from the sodium salts of the alkylsulfonates and alkylphosphonates that are soluble and stable at the working pH of the invention, and is placed in quantities not exceeding 1 g / L, introduced as a prediluted aqueous solution to avoid solubility problems. .

The temperature and current density applied to the solution are parameters that affect the color coordinates, and must therefore be applied within certain ranges and modulated accordingly to the color coordinates to be obtained in the range of interest (L: 65-75 ; a: 6â € “9; b: 10-20).

The preferred working temperature of the solution ranges from 35 to 45 ° C; an increase in temperature causes an increase in gold in the deposit and therefore an increase in the coordinates a and b.

The preferred current density ranges from 0.5 A / dmq to 3 A / dmq, an increase in the applied current density initially causes an alteration of the color and then the appearance of localized burns and non-homogeneity of the deposit.

The duration of the current application does not affect the color, but since it is a color bath, the deposition times can be contained, usually within 2 minutes of application.

The present invention can be better understood in the light of the following embodiment examples.

EXPERIMENTAL PART

Example n ° 1

The following aqueous solution was prepared:

Citric Acid 30 g / L

Potassium Citrate 90 g / L

Tetrasodium HEDP 7 g / L

1 g / L gold entered as potassium dicyanoaurate

Iron 0.6 g / L entered as Iron Citrate

Vanadium 0.6 g / L entered as Vanadium Oxychloride

Tellurium 0.005 g / L entered as Tellurium Oxide

Sodium Laurylether 0.1 mL / L of the 10% w / V solution

A copper sheet measuring 10 x 10 cm, on which a layer of 24 kt gold had previously been deposited, whose color coordinates were (L = 84.8; a = 7.7; b = 30.2) was plated in the laboratory with the solution described above under the following working conditions:

pH 8

0.8 A / dmq

1 minute

The sheet was then rinsed in demineralized water and dried in an oven at 85 ° C for 30 minutes, then allowed to cool to room temperature.

The obtained color coordinates were measured, which turned out to be:

L: 72; a: 7.3; b: 15.2

From electron microscope analysis, the alloy results to have the following composition% by average weight:

Au 89.4%

Fe 6.65%

V 3.95%

You do not enter the league.

Claims (10)

CLAIMS 1. An aqueous solution for electrodeposition of a Gold alloy having color coordinates in the range L: 65-75; to: 6â € “9; b: 10-20; said solution comprising a salt of Gold (Au), a salt of Iron (Fe) and a salt of Vanadium (V), and optionally one or more salts of other metals suitably chosen from the salts of Cobalt (Co), Palladium (Pd ), Ruthenium (Ru), to modulate the shades of the final color; and also optionally comprising small quantities of one or more salts of Tellurium (Te), Gallium (Ga) or Bismuth (Bi), acting as brighteners and grain refiners. 2. Solution according to claim 1 wherein Gold as metal ranges from 0.5 to 3 g / L. Solution according to claim 1 wherein Fe and V as metals are present respectively in concentrations comprised between 0.2 g / L and 1 g / L. 4. Solution according to claim 1 wherein Co, Pd and Ru, if present, are each present in concentrations ranging from 0.005 to 0.5 g / L, wherein the concentrations refer to the metal in solution. 5. Solution according to claim 1 wherein Te, Ga, Bi or their combinations are introduced into the solution in the form of their soluble salts or their complexes stable under the working conditions of the solution, in quantities for each metal in the range 0.005 â € “0.015 g / L as a metal. Solution according to any one of claims 1-5 having a buffered pH between 7 and 10. 7. Solution any one of claims 1-9 comprising one or more complexing agents, in concentrations ranging from 20 to 50 g / L. 8. Solution according to any one of the preceding claims in which a surfactant is present in quantities not exceeding 1 g / L. 9. Method for the electrodeposition of a gold alloy having color coordinates in the range: L: 65-75; to: 6â € “9; b: 10-20; said method comprising the use of a solution according to any one of the preceding claims. 10. A gold alloy, obtained according to the method of claim 12, said alloy having color coordinates in the range L: 65-75; to: 6â € “9; b: 10-20 and having the following composition by weight: Au 86-91%; Fe 6-8% V 4-6% Co, Pd, Ru or 0-0.5% mixtures thereof.