Technical field

The present invention refers to a galvanic deposition process for obtaining the deposit of ruthenium and/or of its alloys, on an object in order to obtain final ruthenium layers with particular colorations, otherwise not obtainable with traditional electro-deposited deposits .

The deposits obtained in this way can be used as a decorative finishing layer, or they can be undergone to a further "re-uncoating" treatment, such as with abrasive ceramic materials, in order to obtain "un-coated" finishing "of vintage type". Short summary of prior art

The production of metal objects or of metal-non- metal compounds can be realized with the use of various well-known technigues which depend on the type of object to be realized.

Only for example and not restrictively, said objects can be realized through the well-known process of galvanic deposition; thanks to it, one or more metallic layers (also of precious metals) can be electro-deposited on a support (for example, an object) made of either a specific composite metal (for example a suitable polymer) or of a specific composite metal non-metal or non-metal metal.

For example, bronze or brass objects are treated through galvanic deposition of suitable metals, in such a manner so as to improve their features of resistance to corrosion, mechanical features, as well aesthetic ones (for example, shininess, smooth or rough appearance, colour), especially if those objects are intended for the industry of fashion or of jewelry in general.

Through such well-known electrolytic process, one or more layers of metallic material/s (even precious) can be deposited on the substrate, so as to obtain the desired final result/object.

Of course, depending on deposited layers of material in terms of number of layers and on the type of used metals, different colorations on the finished object can be obtained.

However, certain colorations or shades of colours (for example, colours such as orange, violet, red, blue or green) are not achievable through this technique and therefore it is often necessary to make a classic coloration with a real dye/varnish.

In case of using varnishes, many remarkable inconveniences have to be considered, as there is a remarkable prolongation of the productive process and a substantial overall increase of costs. In fact, in addition to the phase of colour deposition, often entailing the use of solvents, also a further final phase of colour fixing becomes necessary by means of a hardening phase, preferably a thermal one. Moreover, such process does not prove to be final (the varnish can always degrade or break off) and has also a high environmental impact in terms of pollution and disposal costs.

In addition, the range of colorations achievable with such technology is very scarce.

Finally, it is not possible to obtain finishing "un- coated of vintage type" with such technology. That is, it is not possible to undergo materials/objects coloured through the above-mentioned varnishing to an un-coating treatment, for example with ceramic abrasive materials, in order to obtain "re-uncoated" finishing of vintage type".

Summary of the invention

It is therefore the aim of the present invention to provide an innovative process which solves technical inconveniences highlighted above.

In particular, it is the aim of the present invention to provide a process allowing to obtain particular colorations or shades of colours on metallic objects in general (with metallic or non-metallic base, or hybrid/mixed metallic non-metallic one, as already mentioned above) , said colorations or shades of colours being not obtainable with conventional electro-deposited deposits, without recourse to final varnishing.

These and other aims are therefore obtained through the present process for obtaining the final coloration of an object, according to what is described on the enclosed claims .

The process of the invention comprises substantially a treatment phase of the object mentioned above, by means of a suitable galvanic deposition on it with a suitable metallic element for making the desired final product coloured with colorations, differently not achievable with conventional electro-deposited deposits.

In fact, the applicant has surprisingly found that the formation through suitable galvanic deposition of ruthenium deposits or of its alloys on an object as described beforehand and further, allows to lend the finished product colorations and shades of colour differently not achievable with conventional electro- deposited deposits.

According to the present invention, said ruthenium- based deposits and/or of its alloys, obtained by the process of the invention, can be used as a decorative layer of finishing. In a similar way, according to the present invention, said deposits mentioned above, can also be further undergone to a treatment of un-coating to give uncoated finishes of "vintage" type.

Further advantages of the invention are inferable form the depending enclosed claims.

Disclosure of the invention

Introduction - Definitions

The process of galvanic deposition allows to coat an object made of generally not precious metallic material (for example, copper, brass, bronze), as well as a suitable non-metallic material, or a suitable metallic non-metallic compound, with one or more layers of generally more precious metal/s, by taking advantage of electrolytic deposition.

In a bath, which constitutes the so-called galvanic bath, containing a water-based solution of salt of the metal to be deposited, two electrodes are immerged: the cathode is constituted by the object to be coated, while the anode can be constituted by the metal which has to be deposited (sacrificial anode) , by another inert metal or by graphite. A difference of potential is imposed to such electrodes by means of a power generator. In such conditions, the cations of the metal to be deposited will move towards the cathode (negatively charged) while anions will move towards the anode (positively charged) .

The following phenomena occur to the two electrodes: - Gaining of electrons to the cathode (reduction) - Production of electrons to the anode (oxidation) .

Therefore, cations are deposited on the cathode and they gain electron reducing themselves. In such manner, the cathode is slowly coated by a thin metallic layer while the anode, when is sacrificial, is slowly consumed thus releasing ions in solution. In connection with the metallic layer which has to be deposited and is usually several dozen microns or less, for a predetermined value of current density used by the bath and knowing the deposition speed, it is sufficient to set the necessary period in order to form the deposit of the desired thickness .

The general technique itself however is known and is not further detailed here.

Re-uncoa ting

For the purposes of the present invention, the term

"re-uncoating" means the mechanic process through which part of the superficial layer coating the selected item/object is removed by using suitable abrasive material for this purpose, based on the desired superficial finishing effect.

Tumble finishing

For the purposes of the present invention, the term "tumble finishing" means a superficial finishing process which takes place by means of impacts of pieces inserted in a specific circular vibrator (tumbling barrel), led to vibrate, filled with abrasive material, of size, dimensions and hardness depending on the desired superficial finishing. During the processing, pieces are wet with a specific liquid, commonly known in this field, to make the superficial finishing more homogeneous. As well as the kind of used abrasive, well known to the expert specialist, the rotation speed of the tumbling barrel influences the final effect of the processing.

Vin tage

For the purposes of the present invention, the term

"of vintage type" means a particular type of re-uncoating and/or tumble finishing which simulates an oxidation/natural ageing of the item.

Description

The object of the present invention is a process for obtaining the deposit of ruthenium and/or of its alloys, on an object, said process comprising or consisting at least of the following phases:

1) achievement of an electrolytic bath comprising or consisting of: an aqueous solution of salts of ruthenium and/or ruthenium and metals that can co-deposit with the ruthenium, possibly complexed with suitable complexing agents; conductor salts; any suitable organic and/or inorganic additives;

2) immerse in said bath a cathode constituted by the object which is to be coated by said coloured deposit of ruthenium and/or ruthenium and metals that can co- deposit with ruthenium; and an anode consisting of metallic ruthenium (sacrificial anode) , titanium, platinized titanium, mixed oxides, graphite;

3) applying to said cathode and anode of an effective current intensity for the necessary and sufficient period to secure the coating layer of the object with the desired final coloration.

For the purposes of the present invention, ruthenium is used in the form of pure metal (for example, as a sacrificial anode) , or as a salt thereof, optionally complexed, or together with co-be deposited elements selected from the group consisting of Cr, Mn, Fe , Co, Ni, Cu, Zn, Rh, Pd, Ag, Cd, In, Sn, Pt, Au, Pb, Bi, P, V, Ga, Y, Zr, W; preferably, Fe, Cu, Zn, Rh, Pd, Ag, Sn, Pt, Au, Bi, W; more preferably Fe, Rh, Pd, Ag, Pt, Au, W.

Preferably, the ions of ruthenium salts in the electrolytic bath are selected from the group consisting of: chloride, nitrosilchloride, bromide, iodide, sulfamate, nitrosilnitrate and/or complexing ions, sulfates, sulfamates, phosphates, pyrophosphates, phosphonates , mono-, di- and tri-carboxylates , acetates, citrates, oxalates, gluconates, succinates, glutarates, adipates, tartrates, eptonates, malates, maleates, malonates and/or tetracarboxylic acids such as EDTA (ethylenediaminetetra-acetic acid) ; NTA (nitrilo triacetic acid) and/or their analogous substituted ones.

Said complexing salts are usually used in stoichiometric quantity in respect to the ruthenium or also in an excess in respect to the same quantity.

Preferably, said conductor salts in the electrolytic bath are selected from the group consisting of: sulfates, sulfamates, phosphates, pyrophosphates, phosphonates , mono-, di- and tri-carboxylates , acetates, citrates, oxalates, gluconates, succinates, glutarates, adipates, tartrates, eptonates, malates, maleates, malonates, and/or tetracarboxylic acids such as EDTA (ethylenediaminetetra- acetic acid); NTA (nitrilo triacetic acid) and/or their analogous substituted ones.

The concentration of the salts in the electrolytic bath solution of the invention is usually comprised from 1 to 500 g/L; preferably, from 10 to 400 g/L; more preferably, from 20 to 300 g/L.

Preferably, organic additives in the electrolytic bath are selected from the group consisting of: surfactants, non-ionic, cationic or anionic, anti-pitting agents, brighteners, amphoteric compounds, betaines and solfobetaine, sulfur compounds, aromatics and non, and similar ones, in a variable quantity (based on the experience of the specialist of the field) to be determined case by case, depending on the desired final colour .

Preferably, inorganic additives in the electrolytic bath are selected from the group consisting of: Au, Pd, Rh, Pt, Ag, Ir, Cr, Fe, Co, Ni, Cu, Zn, Cd, In, Sn, Pb, Bi, V, Ga, Y, Zr, Mo, .

The concentrations of said metals in the electrolytic bath solution of the invention are usually comprised from 0.001 g/L to 500 g/L; preferably, from 0.001 to 300 g/L; more preferably, from 0.01 to 200 g/L.

In particular, the concentration of ruthenium, as an element or in form of a salt in the electrolytic bath solution of the invention is comprised from 0.1 g/L to 10 g/L; preferably, from 0.2 g/L to 5 g/L; more preferably, from 0.5 g/L to 3 g/L.

The object (or, as also called further, substrate) that constitutes the cathode is in turn formed from a metal, or a metal alloy, or by more metal layers (precious or non-precious), or by a non-metal (for example a suitable organic polymer) , or a composite metal-non-metal or non-metal-metal suitable to undergo a galvanic deposition process as that of the present invention.

Only for example and not restrictively, said non- metallic substrate can be an organic object, organic- polymer, or an organic-metal composite/organic-polymer- metal (such as an object of a suitable plastic material, coated by one or more layers of metals or metal alloys) able to be undergone to the galvanic process of the present invention.

The metallic substrate is usually selected from the group consisting of Fe, Ni, In, Co, Sn, Cu, Zn, Cr, Bi, Al, V, Mn, Mo, Bi, Au, Ru, Pt, Ag and Pd and/or their alloys; preferably consisting of Fe, Ni, In, Co, Sn, Cu, Zn, Cr, Bi, Al, Au, Ru, Pt, Ag and Pd and/or their alloys; more preferably consisting of Fe, Ni, In, Sn, Cu, Zn, Al, Au, Ru, Pt, Ag, Pd and/or their alloys.

In a preferred form of realization of the invention, said metallic substrate is selected from copper and/or nickel and/or brass and/or bronze and/or zamak (alloy of Zn, Al, Mg, Cu) , as such or conveniently galvanized with additional layers of more noble metals as known over the prior art.

In a further form of realization of the invention it is also foreseen the use of suitable combinations (for example, laminates) or of alloys of the above-mentioned metals, in the suitable quantity, depending on needs.

As concerns the anodes used in the above phase 2) of the process of the present invention, normally the same ones are appropriately selected from those commonly used in the prior art, depending on needs. Only for example, absolutely not limitative of the purposes of the present invention, the anodes can be selected from: soluble electrodes, inert electrodes such as graphite electrodes, mixed oxides, platinized titanium.

In a preferred form of realization of the present invention, the electrodes are selected from those previously described in phase 2) of the process of the present invention.

Preferably, in phase 3) of the process of the present invention, the intensity of the used processing currents is usually comprised from 0.001 A/dm ² to 100 A/dm ² ; preferably, from 0.01 to 50 A/dm ² ; more preferably, from 0.05 to 25 A/dm ² ; even more preferably, from 0.1 to 10 A/dm ² ; even more preferably, from 0.05 to 5 A/dm ² .

Regarding the processing temperature of the electrolytic bath of the present invention, it is comprised from room temperature (about 25°C) to about 80°C depending on the substrate to be treated; preferably, ranging from about 35°C to about 75°C; more preferably, from about 40 °C to about 70 °C; even more preferably, from about 45°C to about 65°C; even more preferably, from about 50°C to about 60°C; in one form of realization, to 55°C.

As concerns the deposition period of ruthenium and/or an alloy thereof with one or more of the previously described metals, this can vary, depending on the temperature of the electrolytic bath, from 0.5 to 15-30 minutes depending on the desired final color.

Only as a non-restrictive example, at a temperature of the electrolytic bath of 55 ° C, the deposition period of ruthenium to obtain an orange colour is 2 minutes; to obtain a purple colour is 4 minutes; to obtain a blue colour is of 6 minutes; to obtain a green colour is of 8 minutes .

According to the present invention, the thickness of the metal layer (ruthenium and/or its alloy) to be deposited is between 0.001 μπι and 10 ym; preferably, between 0.001 μπι and 5 ym; more preferably, between 0.05 and 0.5 m.

The colours obtained with the galvanic deposition process of the present invention described previously, can be, for example regulated from blue to fuchsia, orange, petroleum blue, violet, green by varying conveniently the process parameters of the invention (composition of the electrolytic bath, its temperature, electrodes, applied current intensity, deposition period, and so on) described previously .

In the following experimental section, preparations of a number of objects with different color tones are illustrated, only as an example, absolutely not restrictive of the wide application potential of the invention .

Example of a representative proceeding of the invention :

The electrolytic bath contained:

- 1 g / L of ruthenium (in form of ruthenium trichloride )

- 100 g / L of sulfamic acid

- 1 mL / L of 3-carboxy-l- (phenylmethyl ) pyridinium salt sodium chloride

- 0.5 g / L of thiourea

- Deionized water as required to 1L solution

Electrodes :

Cathode: a plate of 20 mm x 10 mm x 2 mm brass, subjected to a galvanic cycle thus described: copper plating, deposition of white bronze, deposition of gold .

Anode: platinized titanium

Operating conditions :

- Potential difference to the electrodes: 1.3-1.8 V

- Current intensity: 0.3 A / dm ²

- Electrolyte temperature: 55 ° C

- Deposition periods:

for blue colour: 6 minutes

for fuchsia colour: 3 minutes

for orange colour: 2 minutes

for petroleum blue colour: 10 minutes

for purple colour: 4 minutes

for green colour: 8 minutes

The colorimetric parameters (in accordance with the color coordinates CIEL*a*b) result to be the following :

"BLUE" colour:

a = -20.02 ± 2

b = -19.86 ± 4

"FUCHSIA" colour

a = 27.22 ± 2

b = 4.25 ± 4

"ORANGE" colour

a = 29.02 ± 2

b = 30.44 ± 4

"PETROLEUM BLUE" colour

a = -9.73 ± 2

b = -3.27 ± 4

"PURPLE" colour

a = 13.89 1 2

b = -2.53 ± 4

"GREEN" colour

a = -5.50 ± 2 b = 27.7 ± 4

The coloured ruthenium deposits and/or of its alloys obtained as described previously can be advantageously used as a decorative finishing layer of the object on which it was applied (for example, as such or after polishing) , thus improving the aesthetic appearance and the duration.

The so coloured objects are finally washed in water and undergone to drying in a ventilated oven, with temperatures between 35°C and 90°C, preferably between 60°C and 80°C, for periods ranging between 30 minutes and 90 minutes.

Therefore, also these objects covered with a coloured layer of ruthenium and/or an of its alloys obtained through the process of the present invention, are part of the invention itself.

As alternative, said deposits can be undergone to a further treatment, so-called "re-uncoating", for example with the use of abrasive ceramic materials or of known similar substances, in order to obtain a "re-uncoated" finishing "of vintage type".

Only for a not restrictive example, in order to obtain said rediscovered finishing of vintage type, the objects coated by a colored layer of ruthenium and/or an alloy thereof obtained through the process of the present invention are undergone to a known treatment in tumble finishing with one or more abrasive ceramic materials for a variable duration depending on the desired degree of un- coating.

Some of the preferred abrasive ceramic materials are selectable, for example, among the following commercial products: RS 06/06, RS 10/10, RS 10/10/05, RS 02/05 (supplier: Rosier Italiana S.R.L., Concorezzo, IT).

Said products are abrasive ceramic materials of RS quality, namely of high abrasive power, with a specific weight equal to 2.52 g/cm . Referring to the supplier's description, Rosier, ceramics of 06/06 type have "triangular" shape, that is pentahedral with triangular base, with characteristic dimensions of 6 mm x 6 mm (h x w) ; ceramics of type 10/10 have "triangular" shape, that is pentahedral with triangular base, with characteristic dimensions of 10 mm x 10 mm (h x w) ; the ceramic 10/10/05 have "elliptical" form or of a cylinder with an elliptical base with characteristic dimensions of 10 mm x 10 mm x 5 mm (height x major axes of ellipse x minor axis of ellipse); ceramic 02/05 are "cylindrical angular cut"- shape with characteristic dimensions of 2 mm x 5 mm (diameter section x length) .

Operative conditions of the treatment: Machinery;

Circular Vibrator model MB 25 (of Rosier Italiana S.R.L., Concorezzo, IT); specifications of the machinery; 400 V, 50 Hz, 1,500 rpm; Un-coating period: 10-40 minutes, depending on the desired finisihing.

After the un-coating, objects are simply washed and dried, otherwise they can be undergone to (polishing or matting) waxing if it is needed.

Industrial applicability

The present invention has allowed to obtain (metallic and non-metallic) objects coated with final ruthenium layers with particular colorations, not obtainable with traditional electro-deposited deposits, by means of a particular galvanic deposition process of ruthenium and/or of a metallic alloy of it, in such conditions as to provide the desired final coloration.

The deposits obtained in this way can be used as a decorative finishing layer, or they can be undergone to a further "re-uncoating" treatment, such as with abrasive ceramic materials, in order to obtain "un-coated finishing "of vintage type" .