EP0430917B1 - Device for the electrolytic deposition of a continuous layer with a constant thickness - Google Patents

Abstract

Device for forming a continuous electrolytic deposit of uniform thickness on a mobile substrate, in which a cathode consisting of the mobile substrate travels in front of an anode with which it defines an electrolysis gap of small height. The anode consists of a plurality of anode modules (3) mechanically independent of each other. The electrical and/or hydraulic circuits feeding the anode modules (3) comprise flexible members (15) between the stationary sources of current and/or electrolyte and the anode modules. In addition the anode modules are provided with means (4, 9, 10) by which they bear on the cathode (2) or on a surface (1) connected directly to the cathode. The bearing means (4) of at least one anode module (3) preferably comprise means for adjusting the distance between the anode module (3) and the cathode (2) or the surface (1) connected directly to the cathode. These bearing means (4) are, for example, skids or rollers which are optionally fitted at the arm end (9, 10; 13) supporting the anode modules (3). <IMAGE>

Description

The present invention relates to a device for forming a continuous electrolytic deposit of constant thickness on a mobile substrate, such as a moving metal strip. It more particularly aims at achieving a small and regular distance between the anode and the cathode, so as to allow the use of high current densities while limiting the ohmic losses in the electrolyte.

The device of the invention applies both to the deposition of a permanent protective coating on a metal strip and to the manufacture of a thin sheet, then separated from the substrate on which it has been formed. In the description which follows, reference will be made for simplicity to an electrolytic deposit or coating.

It is known that the use of a narrow electrolysis interval, that is to say a short distance between the anode and the cathode, makes it possible to achieve high speeds of circulation of the electrolyte in this interval without requiring too high overall flow rates. It is possible, under these conditions, to apply high current densities, which lead to high yields of electrolytic deposition.

Furthermore, it is also known that a narrow electrolysis interval makes it possible to reduce the electrical losses caused by the resistivity of the electrolyte.

Known, in particular by patents BE-A-905588 and BE-A-08700561, anodes ensuring a short path of the electrolyte in a narrow electrolysis interval, with high turbulence and a low flow rate, and therefore allowing to use high current densities.

Also known, from US-A-2271735, an electrolytic deposition device comprising a circular cathode and an anode constituted by a plurality of anode modules.

However, with the known anodes, there remains a problem concerning the regularity of the electrolysis interval. In fact, the cathode formed by the substrate passes in front of these anodes with a spacing which can vary as a function of deformations, mechanical or thermal, of the substrate itself or of its support and guide rollers. In addition, the geometric shape of the substrate and / or of its support and guide rollers may also have imperfections which have an adverse effect on the regularity of the electrolysis interval.

It is however essential that this electrolysis interval is as regular as possible, that is to say that its variations are kept within as narrow limits as possible. Indeed, these variations acquire a relative importance all the greater as the electrolysis interval is narrower, and this results in corresponding variations in the resistance of the electrical circuit, the current density and finally the efficiency. of the electrolytic deposition process.

The object of the present invention is to propose a device making it possible to remedy this drawback by ensuring the regularity of the electrolysis interval by simple means, even in the event of deformation of the substrate and / or of its support and guide rollers. .

According to the present invention, a device for forming a continuous electrolytic deposit of constant thickness on a mobile substrate, in which a cathode, constituted by said mobile substrate, passes in front of an anode with which it delimits an electrolysis interval of low height , said anode consisting of a plurality of anode modules and having orifices which open into said electrolysis interval, is characterized in that said anode modules are mechanically independent of each other, in that the electric circuits , respectively hydraulic supplying said anode modules have flexible sections between the fixed current sources, respectively electrolyte, and said anode modules, in that said anode modules are provided with means by which they bear on the cathode or on a surface directly connected to the cathode.

It has also been found advantageous, within the framework of the invention, that said support means of at least one anode module comprise means for adjusting the distance between said anode module and the cathode or the surface directly linked to the cahtode.

Within the meaning of the present application, a surface directly linked to the cathode is a bearing surface which is at a known distance, preferably constant, from the cathode. These are, for example, the surface of the drum of a radial electrolysis cell, against which the substrate is applied during its passage through the electrolytic solution; in this case, the distance between the cathode and the surface directly linked to the cathode is equal to the thickness of the product to be coated at any point in the electrolysis interval. In a straight cell, where the cathode substrate follows a rectilinear trajectory in front of the anode, this surface directly linked to the cathode can be materialized in particular by cathode support rollers along its rectilinear trajectory.

The support members are for example constituted by pads with a low coefficient of friction, or by rollers, which slide, respectively which roll on the cathode or on the surface directly linked to the cathode.

According to a particular implementation, the device of the invention comprises an electrolysis cell delimited by an enclosure surrounding at least one anode module

According to a particular embodiment of the device of the invention, said adjustable support means are, at least in part, located inside the electrolysis cell. In this case, at least said part is made of a material resistant to the electrolyte. For example, the parts are made of PTFE (= polytetrafluoroethylene), while the rollers are made of a ceramic material or stainless steel.

In addition, said electrolyte resistant material is preferably electrically insulating, or the members which it constitutes are electrically isolated from the anode and / or the cathode, in order to avoid an anodic attack on these members or on the contrary. a cathodic deposit on these same organs.

According to another embodiment of the device of the invention, said adjustable support means are located outside the electrolysis cell.

This arrangement leaves more freedom for the choice of usable materials and offers greater ease of adjustment; however, it requires sufficient sealing between the inside and outside of the cell, in particular along the mechanical parts which connect the anode modules to their supports, between the active portion and the support portion of the cathode, and possibly along the electrical current inlets to the anode modules.

According to a particular implementation of the device with adjustable support means situated outside the electrolysis cell, said support means comprise hollow arms, which provide both mechanical support and hydraulic supply anode modules. In this case, the anode modules are preferably provided with an individual hydraulic supply, for example from a large section manifold located outside the electrolysis cell.

Fig. 1

présente le principe du dispositif de l'invention, appliqué à une cellule d'électrolyse radiale; la

Fig. 2

montre un exemple de montage d'un module anodique pourvu de moyens d'appui situés à l'intérieur de la cellule; la

Fig. 3

montre un exemple de montage d'un module anodique pourvu de moyens d'appui situés à l'extérieur de la cellule; la

Fig. 4

montre un autre exemple de montage d'un module anodique pourvu de moyens d'appui situés à l'extérieur de la cellule; la

Fig. 5

montre encore un autre exemple de montage d'un module anodique pourvu de moyens d'appui situés à l'extérieur de la cellule; la

Fig. 6

présente un mode de réalisation dans lequel les bras des moyens d'appui extérieurs constituent des éléments du circuit hydraulique.

The detailed description which follows will make it possible to identify other characteristics and advantages of the device of the invention. This description relates to a certain number of particular embodiments of this device which are illustrated in the appended drawings in which the

Fig. 1

presents the principle of the device of the invention, applied to a radial electrolysis cell; the

Fig. 2

shows an example of mounting an anode module provided with support means located inside the cell; the

Fig. 3

shows an example of mounting an anode module provided with support means located outside the cell; the

Fig. 4

shows another example of mounting an anode module provided with support means located outside the cell; the

Fig. 5

shows yet another example of mounting an anode module provided with support means located outside the cell; the

Fig. 6

presents an embodiment in which the arms of the external support means constitute elements of the hydraulic circuit.

These figures constitute schematic representations, without any particular scale, in which only the elements directly necessary for understanding the invention have been reproduced. The directions of fluid flow, both electrical and hydraulic, are indicated by appropriate arrows. Identical or analogous elements, or ensuring identical or analogous functions, are designated by the same reference numerals in all the figures.

Fig. 1 illustrates the principle of the device of the invention in the case of a radial electrolysis cell of the conventional type.

In a manner known per se, the electrolysis cell comprises a cathode, constituted by a roller 1 for deflecting the substrate 2, and an anode arranged opposite at least part of the periphery of the roller 1, at a predetermined distance from that -this.

According to the present invention, the anode consists of a plurality of anode modules 3, mechanically independent of one another, which are each provided with support means 4 on the cathode roller 1 or on the substrate 2. The arrow a indicates the direction of rotation of the roller 1; the arrows b symbolize the mechanical independence of the anode modules 3.

Finally, it will be recalled that, in a cell of this type, the roller cathode 1 and the anode, namely here the anode modules 3, are generally immersed in the electrolyte bath. In the context of the present invention, the anode modules 3 can be constituted by particular anodes of the type described in the aforementioned patents BE-A-905,588 and BE-A-08,700,561.

FIG. 2 shows an example of mounting an anode module 3 provided with support means situated inside the electrolysis cell, seen in direction A of FIG. 1. In this arrangement, the anode modules 3 and their support means 4 are immersed in the electrolyte, symbolized by the hatched area 5. To resist the electrolyte, the metal parts of the cathode and anode modules are of preferably made of titanium or an alloy such as hastelloy or of stainless steel; the support means comprise for example pads 4 in P T F E, which have a low coefficient of friction, while also being insensitive to the electrolyte.

As seen in Fig. 2, the pads 4 are here arranged on either side of the deposition zone 6 corresponding to the substrate 2. The pads 4 can be provided with adjustment means, known per se and not shown here, to vary the distance between the substrate 2 and the anode module 3 and / or to correct the variations in this distance due for example to the wear of the pads 4. By way of example, these adjustment means can be constituted by vertical threaded rods provided with nuts for adjusting the position of the anode module.

Figs. 3 to 5 illustrate various examples of mounting an anode module 3, the support means 4 of which are located outside the electrolysis cell. In this arrangement, the anode module 3 is surrounded by an enclosure 7 which contains the electrolyte 5; this enclosure 7 extends axially over a width at least equal to the width of the deposition zone 6 or of the substrate 2, and on the periphery over at least part of the periphery of the roller 1, to which it is connected by seals rotary seals 8. These seals 8 thus ensure sealing between the active part and the parts for supporting the cathode roller 1. The substrate 2 and the deposition zone 6 are similar to those of FIG. 1. Here again, the entire anode module 3 is seen in the direction A of FIG. 1. The circulation of the electrolyte is ensured by means known per se, in particular by the two aforementioned Belgian patents, which are not part of the present invention and which are therefore not shown.

In Fig. 3, the anode module 3 is provided with two bent arms 9, 10 which pass respectively through the side walls of the enclosure 7 and bear, by their outer end, on the surface of the roller 1. These arms 9, 10 are provided, at their outer end, support means constituted for example by rollers 4, which roll on the roller 1. These rollers are preferably made of a wear-resistant material, such as a ceramic material or a synthetic material such as PTFE, polyethylene (PE) or polypropylene (PP). The tightness of the bushings 11, 12 of the walls of the enclosure 7 by the arms 9, 10 is ensured by any means known per se, for example by flexible membranes or bellows made of a material resistant to the electrolyte such as rubber. , PTFE, PE or P P.

The arrangement of FIG. 4 is substantially identical to that of FIG. 3. The essential difference is that the rotary seals 8 are transferred to the bottom of grooves made in the roller 1. This results in a reduction in the peripheral length of the seals 8, which reduces the risk of electrolyte leakage. ; in addition, the bearing areas of the roller 1 are thus clearly separated from the active area exposed to the electrolyte 5.

Another possible arrangement is illustrated in FIG. 5. Here, the two arms 9 and 10 are joined together in a stirrup spanning the enclosure 7 and resting on the roller 1 by support means such as rollers 4. This stirrup 9, 10 is provided with a central branch 13 which enters the enclosure 7 through a passage 14 pierced in the rear wall of the enclosure 7, and which carries the anode module 3. The sealing of the crossing 14 is also ensured by known means per se such as a flexible membrane or a bellows made of a material resistant to the electrolyte 5.

In the cases, illustrated in particular by FIGS. 3 to 5, where the support means of the anode modules are located outside the electrolysis cell, that is to say in fact outside the enclosure 7, the inlet and the Return of the electrolyte to the enclosure 7 and to the anode modules 3 can be carried out by a conventional hydraulic circuit. However, it has proved advantageous to supply each anode module with electrolyte individually, in order to ensure greater flexibility in the conduct and adjustment of the electrolytic deposition process.

Fig. 6 illustrates a particular arrangement making it possible to supply each anode module with electrolyte individually, the support means of which are located outside the electrolysis cell.

In this arrangement, the arm 10 consists of a tube which is connected to a supply manifold 16 by means of a flexible element such as a bellows 15. The enclosure 7 acts as an outlet manifold , from which the electrolyte 5 is withdrawn by known means, not shown, and optionally returned to the supply collector after an appropriate treatment. The other numerical marks correspond to the identical marks of FIGS. 3 to 5.

This arrangement simplifies the mounting of the anode modules, eliminating at least part of the conventional external hydraulic circuits.

It would moreover not go beyond the scope of the present invention to also ensure the exit of the electrolyte by means of a tubular arm 9 connected to an outlet manifold similar to the supply manifold 16.

It should be understood that the invention is not limited to the modes of particular realization which have just been described and illustrated. Many modifications can be envisaged, in particular in the shape and arrangement of the support means of the anode modules as well as in the arrangement of the anode modules, in particular for their use, mutatis mutandis, with a rectilinear electrolysis cell.

Claims (8)

1. Device for forming a continuous electrolytic deposit of a constant thickness on a movable substrate, device wherein a cathode, which is constituted by the said movable substrate, is moving forward in front of an anode with which it delimits an electrolysis gap of a small height, the said anode being constituted by a plurality of anodic modules and showing orifices which are opening into the said electrolysis gap, characterized in that the said anodic modules (3) are mechanically independent of each other, in that the electric circuits, respectively the hydraulic circuits, which are feeding the said anodic modules (3), comprise flexible sections (15) between the fixed sources of current, respectively of electrolyte, and the said anodic modules, and in that the said anodic modules are provided with means (4, 9, 10) by which they are supported on the cathode (2) or on a surface (1) directly linked to the cathode.
2. Device according to the claim 1, characterized in that the said support means (4) of at least one anodic module (3) comprise means for adjusting the distance between the said anodic module (3) and the cathode (2) or the surface (1) directly linked to the cathode.
3. Device according to any of the claims 1 and 2, characterized in that it comprises an electrolytic cell which is delimited by an enclosure (7) surrounding at least one anodic module (3).
4. Device according to the claim 3, characterized in that the said support means (4) of the anodic modules (3) are located inside the electrolytic cell.
5. Device according to the claim 4, characterized in that the said support means of the anodic modules (3) comprise shoes made of a material presenting a low coefficient of friction.
6. Device according to the claim 3, characterized in that the said support means (4) of the anodic modules (3) are located outside the electrolytic cell.
7. Device according to the claim 6, characterized in that the said support means comprise arms (9, 10, 13) which pass through the walls of the said enclosure (7) and take are supported on the cathode (2) or on a surface (1) directly linked to the cathode.
8. Device according to the claim 7, characterized in that at least one of the arms (9, 10) is constituted by a tube and is used for feeding the electrolyte to, respectively for draining off the electrolyte from the corresponding anodic module (3).

Images