EP2907900A1

EP2907900A1 - Electroplating process and apparatus, particularly for plating or forming parts made of electrically conducting materials by electrodeposition

Info

Publication number: EP2907900A1
Application number: EP14186138.5A
Authority: EP
Inventors: Amulio Liberatori
Original assignee: Italfimet SRL
Current assignee: Italfimet SRL
Priority date: 2014-02-18
Filing date: 2014-09-24
Publication date: 2015-08-19

Abstract

An electroplating process and apparatus (1a, 1b), particularly for plating or forming parts made of electrically conducting materials.

More precisely, the apparatus (1a, 1b) comprises a tank (3), intended to contain a galvanic bath (4) that contains an aqueous solution of the salt of the metal to be deposited, or of the salts of the metals forming the metal alloy to be deposited, and a supporting frame (5), intended to support the parts to be plated (6) and to be connected electrically to the negative pole of at least one power supply (7), the parts to be plated (6) being immersible in the galvanic bath (4).

The particularity of the invention resides in the fact that it comprises a plurality of electrodes (15a, 15b) that can be immersed in the galvanic bath (4) and are connected electrically to a plurality of positive poles of the power supply (7), so as to form a plurality of anodes that are supplied with direct current and independently of each other to generate a flow of a plurality of electric currents, between the electrodes (15a, 15b) and the parts to be plated (6), which is controlled and balanced, with a consequent homogeneity of the thickness of the layer of deposited metal and/or of the titer of the alloy deposited by galvanic effect on the parts to be plated (6).

Description

The present invention relates to an electroplating process and apparatus, particularly for plating or forming parts made of electrically conducting materials.
Currently, the electroplating technique is by now used commonly in many industrial fields and particularly in the jewelry sector for the plating of a part made of a non-precious metal with a precious metal or with a metallic alloy in general.
As is known, an electroplating treatment entails the use of a galvanic bath, containing an aqueous solution of the salt of the metal to be deposited or of the salts of the metals that form the metallic alloy to be deposited, in which two electrodes are immersed between which a difference in potential is applied in order to generate a flow of current between the positively charged electrode, called anode, and the negatively charged electrode, called cathode, through the galvanic bath.
More precisely, during the flow of current, the cations of the metal to be deposited move toward the cathode (negatively charged), whereas the anions move toward the anode (positively charged).
The cations are deposited on the cathode, with which the parts to be plated are associated; by acquiring electrons, the cations are transformed into metallic atoms.
In this manner, the parts to be plated are slowly covered by a thin metallic layer while the anode oxidizes or, when it is sacrificial, is slowly consumed by releasing ions into the solution.
Depending on different variables, such as the quantity of current used, defined as amperes/hour, and the electrodeposition time, it is possible to determine precisely the quantity of metal deposited and therefore, by relating this quantity to the surface of the part to be plated, its average thickness.
Ideally, the more the part to be plated has a simple and less extended geometry, the more the thickness of the metal deposited will be uniform and, in the case of deposition of metallic alloys, the more the titer, defined as percentage of the metals contained in the alloy, will be uniform.
On the other hand, the more the part to be plated has a complex geometry and/or the more it is extended, the more there will be, with equal anodes, substantial differences in the thickness of the layer of the deposited material between one plated area and the other and in the percentages of materials in the titer of the alloy.
All this is due to the fact that the anode, having its own geometry, affects the flow of current and, therefore, the deposition of the cations on the part to be plated.
This influence, which is due mainly to the flow of the current mentioned above, develops preferably at the ends of the anode, where there is a higher intensity of current, creating what is called the point effect.
If, besides an average value of the thickness of the layer of the deposited material, a minimum value or a minimum titer thereof is also required, it is easy to realize the waste of material, with respect to an ideal deposition that is not subject to the variations in thickness of the layer of the deposited material or in the titer of the deposited metallic alloy, due to the point effect.
The aim of the present invention is to devise a process and to provide an electroplating apparatus such as to reduce the thickness variations of the layer of the deposited material or of the titer of the deposited metallic alloy due to the point effect, so as to obtain an almost uniform thickness, reducing to a minimum the waste of material in order to reach the required average value.
Within this aim, an object of the present invention is to devise a process and provide an apparatus for electroplating, particularly adapted to form items of jewelry by electrodeposition.
Another object of the present invention is to devise a process and provide an apparatus for electroplating that are adapted to plate metallic accessories and parts in general made of electrically conducting materials with other precious and non-precious metals or metallic alloys.
A further object of the present invention is to devise a process and provide an apparatus for electroplating that provide the highest assurances of operation and reliability.
Another object of the present invention is to devise a process and provide an apparatus for electroplating that are economically competitive with the background art.
This aim and these and other objects that will become more apparent hereinafter are achieved by an electroplating apparatus, particularly for plating or forming parts made of electrically conducting materials, comprising a tank, intended to contain a galvanic bath that contains an aqueous solution of the salts of the metals to be deposited, and a supporting frame, intended to support the parts to be plated and to be connected electrically to the negative pole of at least one power supply, said parts to be plated being immersible in said galvanic bath, characterized in that it comprises a plurality of electrodes that can be immersed in said galvanic bath and are connected electrically to a plurality of positive poles of said at least one power supply, so as to form a plurality of anodes that are supplied with direct current and independently of each other to generate a flow of a plurality of electric currents, between said electrodes and said parts to be plated, which is controlled and balanced, with a consequently more uniform thickness of the layer of deposited metal and/or a more uniform titer of the alloy deposited by galvanic effect on said parts to be plated.
Further characteristics and advantages of the invention will become more apparent from the description of two preferred but not exclusive embodiments of an electroplating apparatus, particularly for plating or forming parts made of electrically conducting materials, according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic perspective view of a first embodiment of the apparatus according to the present invention;
Figure 2 is a schematic side elevation view of the apparatus shown in Figure 1;
Figure 3 is a schematic perspective view of a second embodiment of the apparatus according to the present invention;
Figure 4 is a schematic side elevation view of the apparatus shown in Figure 3.

With particular reference to the cited figures, the electroplating apparatus, particularly for plating or forming parts made of electrically conducting materials, generally designated in the two proposed embodiments by the reference numerals 1a and 1b, comprises a supporting framework 2 that forms a tank 3 intended to contain a galvanic bath 4 that contains an aqueous solution of the salt of the metal to be deposited or of the salts of the metals forming the metallic alloy to be deposited.
More precisely, the galvanic bath 4 can be made of electrolytic solutions that are known per se and therefore are not described in detail.
Moreover, there is a supporting frame 5 intended to support the parts to be plated 6 and to be connected electrically to the negative pole of at least one power supply 7.
In the proposed embodiments, the supporting frame 5 is associated with a movable arm 8 or 20 adapted to immerse part of the supporting frame 5 and immerse completely the parts to be plated 6 in the galvanic bath 4.
More precisely, in the first embodiment, the supporting frame 5 comprises a rotating drum 9, which has a set of radial elements 10 adapted to support the parts to be plated 6 and a central hub 11 that can be associated with the end of a supporting post 12 arranged centrally and vertically in the tank 3 so as to protrude with its end from the galvanic bath 4.
Advantageously, said supporting post 12 is connected electrically to the negative pole of the power supply 7 and can be associated rotatably with a supporting frame 5 so as to ensure the flow of current from the parts to be plated 6 to said supporting post 12 without interfering with the movement of the rotating drum 9.
To complete the supporting frame 5, motor means 13 are provided, which are known per se and therefore are not described in detail and can be associated with the rotating drum 9 for its rotation about a rotation axis 14 that coincides with the longitudinal axis of the supporting post 12.
Differently, in the second embodiment, the supporting frame 5 comprises a rack 19 that is adapted to support the parts to be plated 6 and extends along a vertical plane that coincides substantially with a plane of symmetry of the region for immersion of the parts to be plated 6.
Advantageously, the rack 19 is associated with the movable arm 20 that is adapted for its alternating movement along a horizontal axis 21 that belongs to the plane of symmetry just mentioned.
According to the invention, a plurality of electrodes 15a or 15b is provided that can be immersed in the galvanic bath 4 and are connected electrically to a plurality of positive poles of the power supply 7, so as to form a plurality of anodes that are supplied with direct current and independently of each other.
In this manner, the flow of a plurality of electric currents is generated between the electrodes 15a or 15b and the parts to be plated 6, said flow being controlled and balanced, with a consequent homogeneity of the thickness of the layer of metal deposited by galvanic effect on the parts to be plated 6 and/or of the titer of the alloy deposited.
More precisely, the power supply 7 is of the modular type and comprises a plurality of power supplies, one for each anode to be supplied, which have a negative pole in common.
Conveniently, said power supplies are provided with current rectifiers so that they can be connected to the electrical grid.
With particular reference to Figures 1 and 2, due to the geometry of the apparatus 1a in the first proposed embodiment, in order to make the deposition of material even more uniform, both in terms of thickness and in terms of titer, and to reduce the electrodeposition time, the electrodes 15a are formed by annular bodies 16 that delimit peripherally the immersion region of the parts to be plated 6, so they are arrangeable in a coaxial manner with respect to the supporting post 12.
More specifically, the annular bodies 16 are mutually stacked vertically so as to be electrically isolated with respect to each other and so as to be arrangeable at the parts to be plated 6 at such a height that it is possible to treat said parts to be plated 6 over their entire vertical extension.
Advantageously, for each annular body 16 there is at least one supporting rod 17, made of a conducting material, adapted to support it and supply it.
More specifically, in this first proposed embodiment, for each annular body 16 there are at least two supporting rods 17 that are mutually connected electrically to the same positive pole of the power supply 7.
More precisely, the supporting rods 17 are arranged diametrically opposite in pairs with respect to the annular bodies 16 so as to supply and support the annular bodies 16 evenly.
Conveniently, the supporting rods 17 are connected electrically at their end portions respectively to the annular bodies 16 and to the positive poles of the power supply 7, with their central portion, formed between the end portions, electrically insulated.
The supporting rods 17 are therefore immersible in the galvanic bath 4 together with the annular bodies 16 so that the end portions connected electrically to the power supply 7 protrude from the galvanic bath 4.
With particular reference to Figures 3 and 4, due to the geometry of the apparatus 1b in the second proposed embodiment, in order to make the deposition of material even more uniform and reduce the electrodeposition time, the electrodes 15b are formed by an even number of rods 18, which are mutually opposite in pairs with respect to the region of immersion of the parts to be plated 6 so as to interpose the rack 19 between the rods 18.
Conveniently, the rods 18 are mutually electrically connected in pairs so as to form a number of anodes that is equal to half the number of the electrodes 15b.
In this manner, there is a double exposure of the parts to be plated 6 with respect to the anodes, with the parts to be plated 6 in alternating motion, speeding up the electrodeposition of the metal to be deposited.
These proposed embodiments can be subject to variations of various kinds linked, for example, to the geometry of the supporting frame 5 or the tank 3 and consisting, for example, in the number and shape of the electrodes 15, without however changing the inventive concept of the present invention.
With this apparatus 1 it is thus possible to provide an electroplating process, particularly for the plating or forming of parts made of electrically conducting materials, that allows the electrodeposition of a layer of metallic material of almost uniform thickness.
More precisely, the electroplating process according to the invention comprises a first step of defining the geometry and the number of the anodes, i.e., of the electrodes 15a or 15b, to be used depending on the dimensions and the geometric shape of the parts to be plated 6, a second step for defining the value of the total current that flows between the anodes and the cathode, constituted by the supporting frame 5, and the electrodeposition time depending on the required quantity and thickness of metal.
Once these essential aspects have been defined, one moves on to a third step in which, thanks to the modular power supply 7, the total current is divided over the individual anodes so as to supply each one with a specific current, such that the sum of these specific currents is equal to the total current.
In other words, the individual anodes are supplied in a mutually independent manner in order to form an equivalent dummy anode that has larger dimensions than the anodes taken individually and is charged uniformly and capable of generating a current flow while remaining free from any type of point effect.
Subsequently, one moves on to the immersion of the parts to be plated 6 and their movement, applying the specific currents to the anodes for the preset electrodeposition time.
In practice it has been found that the electroplating process and apparatus, particularly for plating or forming parts made of electrically conducting materials, according to the invention, achieve fully the intended aim and objects, since they allow a plating of a part with metallic material, obtaining almost uniform thicknesses and, in the case of deposition of metallic alloys, a titer of the alloy, defined as a percentage of the metals contained in it, that is almost uniform, in accordance with the required minimum and average values, without any waste of material.
Another advantage of the electroplating process according to the invention resides in maximum flexibility and efficiency of use, by allowing constructive but not conceptual variations, depending on the geometry of the part to be treated.
The electroplating process and apparatus, particularly for plating or forming parts made of electrically conducting materials, thus conceived, are susceptible of numerous modifications and variations, all of which are within the scope of the accompanying claims.
All the details may furthermore be replaced with other technically equivalent elements.
In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.
The disclosures in Italian Patent Application No. AR2014A000011 from which this application claims priority are incorporated herein by reference.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

An electroplating apparatus (1a, 1b), particularly for plating or forming parts made of electrically conducting materials, comprising a tank (3), intended to contain a galvanic bath (4) that contains an aqueous solution of the salts of the metals to be deposited, and a supporting frame (5), intended to support the parts to be plated (6) and to be connected electrically to the negative pole of at least one power supply (7), said parts to be plated (6) being immersible in said galvanic bath (4), characterized in that it comprises a plurality of electrodes (15a, 15b) that can be immersed in said galvanic bath (4) and are connected electrically to a plurality of positive poles of said at least one power supply (7), so as to form a plurality of anodes that are supplied with direct current and independently of each other to generate a flow of a plurality of electric currents, between said electrodes (15a, 15b) and said parts to be plated (6), which is controlled and balanced, with a consequent homogeneity of the thickness of the layer of deposited metal and/or of the titer of the alloy deposited by galvanic effect on said parts to be plated (6).
The apparatus (1a, 1b) according to claim 1, characterized in that said at least one power supply (7) is of the modular type and comprises a plurality of power supplies, one for each anode to be supplied, which have said negative pole in common, said power supplies being provided with current rectifiers so that they can be connected to the electrical grid.
The apparatus (1a) according to claims 1 or 2, characterized in that said electrodes (15a) are formed by annular bodies (16) that delimit peripherally the immersion region of said parts to be plated (6), said annular bodies (16) being mutually stacked vertically so as to be electrically isolated from each other and being arrangeable at said parts to be plated (6) at such a height that it is possible to treat said parts (6) to be plated over their entire vertical extension.
The apparatus (1a) according to one or more of the preceding claims, characterized in that it comprises at least one supporting rod (17), made of a conducting material and adapted to support a respective one of said annular bodies (16), said supporting rods (17) being connected electrically at their end portions respectively to said annular bodies (16) and to said positive poles of said at least one power supply (7) and having a central portion, formed between said end portions, that is electrically insulated, said supporting rods (17) being immersible in said galvanic bath (4) together with said annular bodies (16) so that said end portions connected electrically to said at least one power supply (7) protrude from said galvanic bath (4).
The apparatus (1a) according to one or more of the preceding claims, characterized in that it comprises a supporting post (12) that is arranged centrally and vertically in said tank (3) so as to be substantially coaxial with said annular bodies (16) and protrude with its end from said galvanic bath (4), said supporting post (12) being connected electrically to said negative pole and being able to be associated rotatably with said supporting frame (5) so as to ensure the passage of current from said parts to be plated (6) to said supporting post (12).
The apparatus (1a) according to one or more of the preceding claims, characterized in that said supporting frame (5) comprises a rotating drum (9) that has a set of radial elements (10) adapted to support said parts to be plated (6) and a central hub (11) that can be associated with the end of said supporting post (12).
The apparatus (1a) according to one or more of the preceding claims, characterized in that it comprises motor means (13) that can be associated with said rotating drum (9) for its rotation about a rotation axis (14) that coincides with the longitudinal axis of said supporting post (12).
The apparatus (1b) according to claims 1 or 2, characterized in that said electrodes (15b) are formed by an even number of rods (18), which are mutually opposite in pairs with respect to the region of immersion of said parts to be plated (6) and are electrically mutually connected in pairs so as to form a number of anodes that is equal to half the number of said electrodes (15b).
The apparatus (1b) according to claim 7, characterized in that said supporting frame (5) comprises a rack (19) that is adapted to support said parts to be plated (6) in such a manner that it is interposed between said rods (18), said rack (19) extending along a vertical plane that coincides substantially with a plane of symmetry of said immersion region of said parts to be plated (6) and being associated with a movable arm (20) that is adapted for the alternating movement of said rack (19) along a horizontal axis (21) that belongs to said plane of symmetry.
An electroplating process, particularly for plating or forming parts made of electrically conducting materials, by means of an apparatus (1a, 1b) according to one or more of the preceding claims, characterized in that it comprises the steps of:
- defining the geometry and the number of said anodes to be used as a function of the dimensions and the geometric shape of said parts to be plated (6),

- defining the value of the total current that circulates between said anodes and said cathode and the electrodeposition time as a function of the quantity and thickness of metal required,

- dividing said total current over said anodes, so as to supply each one of said anodes with a specific current, such that the sum of said specific currents is equal to said total current,

- immersing said parts to be plated (6) and moving them,

- applying said specific currents to said anodes for said electrodeposition time.