EP0294358A2 - Electrode for an electrolytic cell - Google Patents

Abstract

Electrode for an electrolysis cell intended for the deposition of a metal coating on a substrate. It comprises an electrode body which has at least one surface profiled in a manner corresponding to the surface of the said substrate; the electrode body has a plurality of parallel narrow slots which open into the profiled surface and which are connected to transverse channels joined alternatively to means for feeding or removing electrolyte. The transverse channels (9, 10) are defined by profiles (2, 11) arranged parallel to each other and at some distance from each other; these profiles have at least one profiled face (7) and are attached individually to a support (3) so that the profiled faces constitute the profiled surface of the electrode body. <IMAGE>

Description

The present invention relates to an electrode intended for an electrolysis cell of the type used in particular for depositing a metallic coating, adherent or detachable, on a substrate.

The efficiency of an electroplating operation as well as the quality of the deposit formed require the use of a high current density. Indeed, this conditions on the one hand the duration of the operation, that is to say the speed of the substrate and the size of the deposition installation if the substrate is in motion, and on the other hand apart from the compactness, or conversely the porosity, of the coating deposited.

Achieving high current densities, for example greater than 100 A / dm², requires high turbulence, that is to say a high speed, of the electrolyte in the space between the anode and the cathode. In addition, it is desirable to reduce as much as possible the energy losses by Joule effect, both in the electrolyte and in the power supply circuits. To this end, it is necessary on the one hand to minimize the distance between the anode and the cathode of the cell, and on the other hand to ensure the electrical supply of the anode by means of low resistance conductors up to proximity the interval between the anode and the cathode.

There are already, in the art, numerous arrangements of electrolysis cells associated with various methods of introducing the electrolyte between the anode and the cathode.

Reference may in particular be made to patent application BE-A-08700561 from the same applicant, which describes an electrode comprising an electrode body provided with a plurality of parallel narrow slots serving, in alternating arrangement, respectively for supplying and to the discharge of the electrolyte.

Further research by the applicant has however shown that this known electrode did not yet make it possible to obtain with certainty a deposit having a sufficiently uniform thickness along the width of the substrate. It has indeed appeared that the electrolyte pressure increases from the open end to the closed end of the supply channels; this results in a variable speed of circulation of the electrolyte in the deposition interval and consequently a deposition thickness which is not uniform over the width of the substrate.

From this state of the art, the present invention provides an electrode for an electrolysis cell, in particular an anode, which makes it possible to remedy the aforementioned drawback and which therefore ensures the formation of a thick coating. uniform, both in the longitudinal and transverse directions. This improvement is achieved, thanks to the invention, without adversely affecting the advantageous aspects of the known electrode, in particular the short path of the electrolyte between the anode and the cathode.

According to the present invention, an electrode for an electrolysis cell intended for depositing a metal coating on a substrate, which comprises an electrode body comprising means for supplying electric current and having at least one profiled surface of corresponding to the surface of said substrate, said electrode body having a plurality of parallel narrow slots which open into said profiled surface and which are connected to transverse channels connected alternately to means for supplying, respectively discharging, the electrolyte, is characterized in that said transverse channels are delimited by profiles arranged parallel to one another and to a certain distance from each other, in that said profiles have at least one profiled face and in that said profiles are individually fixed to a support so that said profiled faces constitute said profiled surface of the electrode body.

According to the invention, seals are provided between the profiles and the support, so as to prevent any contact between the means for fixing the profiles to said support and the electrolyte.

According to a particular embodiment of the invention, said sections are of type I and they are separated from said support by means of rectilinear joints placed transversely.

In such an arrangement, each profile separates a supply channel and an electrolyte discharge channel, and the rectilinear seals contribute to this separation by preventing any passage of electrolyte between a profile and the support. .

According to an interesting alternative embodiment of the invention, said profiles are of the U type and they are provided, at the end of at least one of the wings, with a sole bearing said profiled face.

With such an arrangement, the internal volume of a U-shaped profile preferably constitutes a supply channel, while the volume comprised between two profiles forms a channel for discharging the electrolyte. Only the mechanical fixing means and / or electrical connection of the profiles are here surrounded by seals, which are thus only subjected to the low pressure prevailing in the electrolyte discharge channels. It would obviously not go beyond the scope of the invention to provide the supply channels between the profiles and the evacuation channels inside these profiles.

In the context of the present invention, the electrode may have different means to guarantee the formation of a deposit of uniform thickness along the width of the substrate.

It has already been indicated above that the supply channels closed at one end cause an increase in the electrolyte pressure in the vicinity of this closed end. The present invention proposes to modify the geometry of the slots and / or supply channels, in order to minimize the effects of this increase in the pressure of the electrolyte.

In a first embodiment, an electrolyte supply channel has a variable cross section in the direction of its closed end. Such a variation in section makes it possible to compensate for the increase in pressure and consequently to eliminate the unfavorable effects.

Another embodiment consists in varying the width of the feed slots towards the closed end of the corresponding feed channel. Such a variation in width makes it possible to standardize the speed of the electrolyte, and consequently its turbulence, along the width of the substrate.

According to yet another embodiment, the surface of the body of the anode is profiled transversely so that the deposition interval corresponding to at least one supply channel has a variable thickness in the direction of the closed end of this channel. Such a variation in thickness also has the effect of modifying the passage section and thus limiting the increase in the speed and the turbulence of the electrolyte along the width of the substrate.

It would moreover not depart from the scope of the present invention to combine at least two of these embodiments, or to carry out corresponding modifications in the slots and / or the electrolyte discharge channels.

Still according to the invention, the channels are grouped in pairs, each pair comprising a supply channel and an electrolyte discharge channel, the two channels of the same pair are closed at one of their neighboring ends and are connected at their other end to means for supplying or discharging the electrolyte, respectively, and said pairs of channels are arranged head to tail, the closed ends of the channels of any one of said pairs being close to the ends open channels of said adjacent pair or pairs.

According to another arrangement, each channel is connected by its two ends to means for supplying, respectively discharging, the electrolyte, the supply channels and the discharge channels alternating successively in the longitudinal direction of the 'electrode.

According to yet another arrangement, the two ends of each channel are closed, and the means for supplying, respectively discharging, the electrolyte are connected at several points distributed transversely relative to the substrate, along the length of the respective channels.

Of course, it would not be departing from the scope of the invention to combine several of these arrangements, for example by providing a supply, respectively a discharge, of the electrolyte both by the ends and by the transverse points in at least one part of said channels, possibly in combination with a variation of one or the other geometric characteristic, as indicated above.

In particular, an advantageous arrangement consists in ensuring a supply under a different pressure in the region of the edges of the substrate, in order to compensate for a variation in the thickness of the deposit due to the proximity of the edges of said substrate.

According to a particular advantageous embodiment, said means for supplying, respectively discharging, the electrolyte comprise a plurality of identical longitudinal elements which each have their own mechanical fixing means and their own electrical connection means. Such elements are juxtaposed in the transverse direction of the substrate, in a number corresponding to the largest width of substrate to be treated in the installation.

In accordance with this particular embodiment, each of said elements advantageously consists of two elongated boxes secured by a side wall, one of said boxes being connected to an electrolyte supply pipe while the other box is connected to a discharge pipe for the electrolyte; said boxes are arranged substantially horizontally under the support carrying said transverse profiles. The supply box is provided, in its upper face, with openings putting it in communication with the supply channels, while the discharge box is provided, in its upper face, with holes putting it in communication with the drainage channels.

Each longitudinal element is individually fixed to the support on which the profiles are mounted. All of said elements can itself constitute the support; in this case, the longitudinal elements are fixed directly to the underside of said profiles, with the interposition of the seals indicated above.

Each of said longitudinal elements has its own supply and its own electrolyte discharge; it therefore makes it possible to modulate or possibly interrupt this supply as a function of the width of the substrate, in particular in the elements corresponding to the edges of the substrate. The connection of the supply lines is advantageously carried over to the ends of the said elements, so as to facilitate the connection of the evacuation lines to the lower part of the said elements.

Each of said longitudinal elements also has its own power supply, which is advantageously constituted by a longitudinal conductive plate disposed between the two boxes constituting said element. This plate is preferably connected at its ends to a source of electric current, which also contributes to clearing the space located under said element. Such a plate also plays a role of stiffener of the longitudinal element. The power supply can also be modulated independently for each element.

• Figure 1 représente, en perspective, un corps d'électrode constitué de profilés I conformément à l'invention; la
• Figure 2 montre une coupe verticale prise suivant la ligne I-I de la Fig. 1; la
• Figure 3 illustre en coupe une partie d'un corps d'électrode constitué de profilés U; la
• Figure 4 montre un moyen de fixation et de raccordement des profilés à un support, respectivement à un circuit électrique; la
• Figure 5 illustre en élévation et en plan, chaque fois en coupe, diverses variations des caractéristiques géométriques; la
• Figure 6 représente quelques possibilités de raccordement des canaux aux moyens d'alimentation, respectivement d'évacuation de l'électrolyte; et la
• Figure 7 montre, en coupe, la section transversale d'un élément longi­tudinal assurant l'alimentation et l'évacuation de l'électrolyte.

Other characteristics and advantages of the present invention will appear on reading the description of various embodiments of an electrode, given below by way of example and with reference to the accompanying drawings, in which the

• Figure 1 shows, in perspective, an electrode body consisting of profiles I according to the invention; the
• Figure 2 shows a vertical section taken along line II of Fig. 1; the
• Figure 3 illustrates in section a part of an electrode body consisting of U profiles; the
• Figure 4 shows a means of fixing and connecting the profiles to a support, respectively to an electrical circuit; the
• 5 illustrates in elevation and in plan, each time in section, various variations of the geometric characteristics; the
• Figure 6 shows some possibilities of connecting the channels to the supply means, respectively evacuation of the electrolyte; and the
• Figure 7 shows, in section, the cross section of a longitudinal element ensuring the supply and evacuation of the electrolyte.

These figures are schematic representations, in which the same elements or corresponding elements are designated by the same reference numerals. The directions of flow of the electrolyte are indicated by arrows.

Referring to Figure 1, there is shown an anode portion, generally designated by the reference numeral 1, composed of several sections in I 2. These sections are arranged parallel to each other and transversely to the substrate (not shown) whose longitudinal dimension, or the direction of movement if it is mobile, is symbolized by the arrow A. The sections 2 are attached to a support 3 by fixing means not shown in Figure 1, with interposition of seals 4 rectilinear and arranged transversely to the substrate.

Figure 2 shows a vertical section along line II of Figure 1, through the anode portion 1 consisting of parallel sections 2. These sections are separated by a distance "e" which constitutes the width of a slot d supply, respectively discharge, of the electrolyte. This distance "e" can also be different depending on whether it corresponds to a feed slot or to a discharge slot. The profiles 2 are individually attached to a support 3 by fixing means, symbolized here by nuts 5, which will be described in detail below. These fixing means can also be used to ensure the electrical supply of the anode.

Seals 4 are arranged between the rear face 6 of the profiles and the support 3. The profiles have at least one face 7, called the front face, the layout of which corresponds to the shape of the surface of the substrate, which surface is symbolized by the dashed line 8. The volumes between the sections alternately constitute supply channels 9 and discharge 10 of the electrolyte, indicated respectively by arrows B and C. The seals 4 prevent communication on the one hand electrolyte from a supply channel 9 to a neighboring discharge channel 10 and on the other hand any contact of the electrolyte with the means of fixing and / or electrical supply of the profiles 2. These means are not therefore not exposed to corrosion by the electrolyte.

In Figure 3, there is shown a part of an electrode body consisting of U-shaped profiles, according to an interesting implementation of the invention. These sections, marked 11, are fixed to a support 3, with the interposition of seals 4, by fixing means 13 which will be described in detail below. At the end of the wings of the profiles 11 are mounted plates 12 parallel to the substrate 8, so as to leave between them a slot of width e or e ′, respectively inside a profile or between two neighboring profiles. These widths e, e ′ can be equal or different. The interior space of each profile 11 constitutes a supply channel 9 where the electrolyte arrives at a high pressure (arrow B); in this channel, the electrolyte is not in contact with any seal. The discharge channels are formed by the spaces 10 between the sections 11 and in which the electrolyte circulates under low pressure (arrow C). The seals 4 are in contact only with the electrolyte under low pressure; they protect the fastening means against any contact with the electrolyte.

In FIGS. 1 to 3, the support 3 may constitute the bottom of a supply collecting basin, respectively for discharging the electrolyte, a basin which is not shown in these figures.

The fixing means symbolically designated by 5 in FIG. 2 and by 13 in FIG. 3 ensure both the individual fixing of the sections 2, 11 to the support 3 and the electrical connection of these sections to an appropriate current source not shown. . FIG. 4 illustrates a particular embodiment of these fixing and connection means, which on the one hand ensures an electrical contact with low resistance and an arrival of current to the supply channel and which on the other hand allows individual disassembly easy of each profile by simple loosening of nuts located outside the electrolyte circuit. Several fixing means of this type are provided distributed over the length of the profiles.

FIG. 4 shows, by way of example, the mechanical fixing and the electrical connection of a profile 2 to a support 3 with interposition of seals 4. A threaded rod 13 passes through the support 3 and is screwed into the base profile 2; it is surrounded by the seals 4 and is therefore not exposed to contact with the electrolyte. On this threaded rod are then mounted a washer 14, a conductor 15, such as a flat cable or a copper bar, a second washer 16 then a nut 17 which provides the tightening required for the mechanical fixing and the electrical connection. It is advantageous to use a flexible flat cable which gives the electrode a certain freedom of movement relative to the source of electric current, generally fixed.

FIG. 5 illustrates the variation of three geometric characteristics of the electrode, namely (a) the width of a channel, (b) the width of a slot and (c) the thickness of the deposition interval. In each case, it presents an elevation view, which is a vertical section along line B-B, and a plan view, which is a horizontal section along line C-C. These variations make it possible to standardize the pressure and consequently the speed of the electrolyte and thus the thickness of the deposit along the width L of the substrate, shown diagrammatically in phantom.

Finally, FIG. 6 illustrates various possibilities for connecting the channels of the electrode to the supply means, respectively the discharge of the electrolyte.

FIG. 6a shows, in plan, a set of four successive channels 18, 19, 20, 21, closed at one of their ends, and grouped in pairs arranged head to tail. The lines such as 22 drawn inside these channels symbolize the supply and discharge slots respectively. Each pair of channels comprises a feed channel and a discharge channel, indicated respectively by the incoming arrows D and outgoing E. In this arrangement, the inlet of the feed channel of a pair is adjacent to the outlet of the drain of the same pair while it is adjacent to the end closed of the drainage channel of the neighboring pair. A similar arrangement prevails for the evacuation channel of a pair with respect to the neighboring supply channels.

In the arrangement of FIG. 6b, the channels do not have a closed end and they are connected alternately and by their two ends to supply means (arrows D), respectively of evacuation (arrows E) of the electrolyte.

FIG. 6c shows in elevation, two successive channels connected to supply means (arrows D), respectively of evacuation (arrows E), of the electrolyte. The connection points are appropriately distributed along the width of the substrate to obtain the desired distribution of the speed of the electrolyte and therefore of the thickness of the deposit.

The arrangement illustrated in FIG. 6d constitutes a combination of the two preceding solutions (FIGS. 6b and 6c), which makes it possible to modulate the flow rate of the electrolyte to take account in particular of a possible influence of an edge effect on the regularity of the thickness of the deposit in the vicinity of the edges of the substrate.

FIG. 7 illustrates, in cross section, a longitudinal element constituting a particular embodiment of the invention. Said element consists of two elongated boxes 23, 24, assembled by welding to the underside of the support 3. As an indication, there is shown in phantom a profile 2 and a rectilinear seal 4. The two boxes are secured by a side wall, by means of a conductive plate 25, this plate itself being welded to the support 3 to ensure good electrical contact. In the illustrated configuration, the box 23 is the discharge box which is provided with a line 26 for discharging the electrolyte. The supply of electrolyte to the supply box 24 as well as the electrical supply to the plate 25 are carried over to the ends of the element and are not shown here.

An electrode formed by individual profiles, in accordance with the present invention, offers many advantages. It makes it possible in particular to take account of slow phenomena, such as the wear of the rollers or of the slots, as well as rapid phenomena such as a rupture of a profile or of a fastener, by facilitating the disassembly and the replacement of the profile. damaged. It makes it possible to associate the mechanical fixing and the electrical connection of the profiles at a sufficient number of points distributed along the width of the substrate; however, it also makes it possible to dissociate these two functions, by fixing the profiles to the support and independently connecting this support to the source of electric current. It also offers the possibility of modulating the supply of electrolyte and electric current to guarantee the homogeneity and transverse uniformity of the deposit.

The invention is not strictly limited to the embodiments which have just been described and illustrated by way of simple example. On the contrary, it also includes equivalent solutions falling within the scope of the claims which follow.

Claims (14)

1. Electrode for an electrolysis cell intended for depositing a metal coating on a substrate, which comprises an electrode body comprising means for supplying electric current and having at least one surface profiled corresponding to the surface of said substrate, said electrode body having a plurality of narrow parallel slots which open into said profiled surface and which are connected to transverse channels alternately connected to means for supplying, respectively discharging, the electrolyte, characterized in that said transverse channels are delimited by profiles (2; 11) arranged parallel to one another and at a certain distance from each other, in that said profiles have at least one profiled face (7 ) and in that said profiles are individually fixed to a support (3) so that said profiled faces constitute said profiled surface of the electrode body. 2. Electrode according to claim 1, characterized in that it comprises seals (4) between the profiles and the support, said seals preventing any contact between the means for fixing the profiles to said support and the electrolyte. 3. Electrode according to either of Claims 1 and 2, characterized in that the said sections (2) are of type I and in that they are separated from the said support by means of rectilinear joints placed transversely to the substrate. 4. Electrode according to either of Claims 1 and 2, characterized in that the said profiles (11) are of type U, and in that they are provided, at the end of at least one of the wings, of a sole (12) carrying said profiled face, the internal volume of said U-shaped profiles being connected to said means for supplying, respectively discharging, the electrolyte, while the volume included between two sections is connected to said means for discharging, respectively supplying, the electrolyte. 5. Electrode according to either of the preceding claims, characterized in that at least one supply channel and / or at least one electrolyte discharge channel has a closed end and in that its cross section varies in the direction of said closed end. 6. Electrode according to either of the preceding claims, characterized in that at least one supply channel and / or at least one electrolyte discharge channel has a closed end and in that the width of the feed slot connected to said channel varies in the direction of said closed end. 7. Electrode according to either of the preceding claims, characterized in that at least one supply channel and / or at least one channel for discharging the electrolyte has a closed end and in that said surface of the electrode body is profiled transversely so that the deposition interval corresponding to said feed channel has a variable thickness in the direction of said closed end. 8. Electrode according to either of claims 1 to 7, characterized in that the channels are grouped in pairs, each pair comprising a supply channel and an electrolyte discharge channel, in that the two channels of the same pair are closed at one of their neighboring ends and are connected, by their other end, to means for supplying, respectively discharging the electrolyte, and in that said pairs of channels are arranged head to tail, the closed ends of the channels of any one of said pairs being close to the open ends of the channels of said adjacent pair or pairs. 9. Electrode according to either of Claims 1 to 4, characterized in that each channel is connected by its two ends to supply means, respectively for discharging the electrolyte, the supply channels and the discharge channels alternating successively in the longitudinal direction of the electrode. 10. Electrode according to either of claims 1 to 4, characterized in that the two ends of each channel are closed, and in that the means for supplying, respectively discharging, the electrolyte are connected at several points distributed transversely to the substrate, along the length of the respective channels. Electrode according to either of the preceding claims, characterized in that the said means for supplying or discharging the electrolyte respectively comprise a plurality of identical longitudinal elements, in that each of the said elements has its own means mechanical fixing and its own electrical connection means, and in that each of said elements is connected to a supply line and to an electrolyte discharge line, said rectilinear elements being juxtaposed in the transverse direction of the substrate. 12. Electrode according to claim 11, characterized in that each of said elements consists of two elongated boxes secured by a side wall, one of said boxes being connected to an electrolyte supply line while the other box is connected to a electrolyte discharge pipe, in that said boxes are arranged substantially horizontally under the support carrying said transverse sections, in that said supply box is provided, in its upper face, with holes putting it in communication with the supply channels and in that said evacuation box is provided, in its upper face, with holes putting it in communication with the evacuation channels of the electrolyte. 13. Electrode according to claim 12, characterized in that said element comprises a longitudinal conductive plate disposed between the two boxes, in that the two boxes are secured by means of said plate and in that this plate is connected by its ends to a source of electrical current. 14. Electrode according to either of claims 11 to 13, characterized in that the number of said identical longitudinal elements is adapted to the width of the substrate to be coated.

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