EP0694090A1

EP0694090A1 - Process and device for the electrolytic surface coating of workpieces

Info

Publication number: EP0694090A1
Application number: EP94905645A
Authority: EP
Inventors: Rudolf Kamm
Original assignee: Ecograph AG
Current assignee: Ecograph AG
Priority date: 1994-02-15
Filing date: 1994-02-15
Publication date: 1996-01-31
Anticipated expiration: 2014-02-15
Also published as: AU5968594A; US5716509A; EP0694090B1; WO1995021952A1; DE59402538D1

Abstract

In the novel and advantageous process for electrolytically surface-coating special metal workpieces it is important for the electrolyte to be conveyed in a controlled circuit in and around the electrolysis region in which most of it is conveyed at a high flow rate, possibly at a higher inlet pressure, through the space between the cathodically connected workpiece and the anode and a smaller proportion of it is conveyed at a lower flow rate upwards to the rear of the anode away from the cathode. After leaving the electrolysis region the electrolyte is taken into a separate overflow tank and conveyed therefrom again into and around the electrolysis region between the anode and the cathode. Anode sludge is separated off in the overflow tank and/or in the feedback system. The device for implementing said process has an actual electrolysis tank (1.01), inlet lines (1.05) or apertures (1.06, 1.07) for the electrolyte at the base of the chamber between the cathodically connected workpiece (1.04) and the anode (1.03) or below behind the anode, at least one overflow tank (1.08) connected on or beneath the electrolysis container into which the electrolyte is fed after passing though the electrolysis region and a feedback device for the electrolyte with a filter (1.11).

Description

METHOD AND DEVICE FOR THE ELECTROLYTIC SURFACE COATING OF WORKPIECES

The invention described here relates to a method and a device for the electrolytic surface coating of objects conducting electrical current, in particular metal workpieces, and a special use of the device mentioned.

Electrolytic surface coatings of metallic objects have long been part of the known prior art; The technology mentioned is widely represented in the patent literature.

Recent, relevant, published patent applications include EP-A 0 196 420, EP-A 0 387 750 and DE-A 34 29 890.

EP-A 0 196 420 (publication date October 8, 1986) teaches a high-speed electrolysis cell for the surface coating of strip-like material. Said device comprises a vertical electrolytic galvanizing cell for coating steel strips, in which the strip is guided from an upper deflection or current roller to a lower deflecting immersion roller and from there to a further, upper deflection or current roller. there is applied to the device to be coated ascending and descending strip section in a gap between vertically positioned anodes of the geführ¬ in circulation th Eletrolytstrom at high speed against the tape ^¬. In such an electrolysis cell, the circulation of large amounts of electrolyte is achieved using the lowest possible pump energy.

According to EP-A 0 387 750 (publication date September 19, 1990), the electrolysis cell described therein is specified by a plurality of current feeds and a plurality of electrolyte feeds or discharges. This ensures uniform electrolysis and coating.

Finally, the device from DE-A 34 29890 is used to apply a copper layer to a gravure cylinder in a galvanizing bath, which has a copper-containing electrolyte and at least one anode body made of copper. The anode body can have the shape of a plate provided with a plurality of openings, especially that of a perforated or expanded metal plate concentrically arranged around the pressure cylinder. This arrangement allows the electrolysis to be carried out under a relatively low voltage and an even copper layer to be applied to the cathodically connected intaglio cylinder.

What the three above-mentioned teachings have in common is that they do not pay sufficient attention to the conceptual elimination of the anode sludge. However, as attempts by the applicant have clearly shown, the solution to this problem leads to a uniformity, i.e. homogeneous, fine crystalline structure as well as corrosion resistance, significantly improved quality of the electrically applied surface layer.

The method according to the invention for the electrolytic surface coating of electrically conductive, in particular metal workpieces, by means of a fluid electrolyte is characterized in that - That the electrolyte is conveyed in a controlled circulation in and around the electrolysis zone between the anode and the cathodically connected workpiece, the electrolyte for the most part at a high throughput rate, possibly under a higher inlet pressure, through the space between the cathodically connected workpiece and the anode and, to a lesser extent, with a lower throughput rate on the rear side of the anode facing away from the cathode,

- That the electrolyte is led into a separate overflow tank after leaving the electrolysis zone and

that the electrolyte is conveyed from the overflow tank back into and around the electrolysis zone between the anode and cathode,

anode sludge being separated or separated from the electrolyte in the overflow tank and / or in the return device.

In the above-mentioned method, it is also relevant that the electrolyte is brought up to the anode, through the anode or is removed from the anode in such a way that the major part of the anode sludge which forms during the electrolysis is carried away by the flowing electrolyte.

Advantageously, the electrolyte on the circulation is continuously checked with regard to the essential process parameters such as temperature, conversion, contents, etc. and, if necessary, optimized.

The cathodically connected workpiece is either fixed or it is moved, in particular rotated, during the electrolytic surface coating; the anode is either replaced periodically or the anode material is continuously updated.

As said, the anode sludge is separated or separated from the electrolyte during its passage through the overflow tank either by settling and / or by electrodes, and / or the sludge particles are retained on a filter connected to the return conveyor.

The device according to the invention for the electrolytic surface coating of electrical conductors, in particular

Metal workpieces, by means of a fluid electrolyte, are marked

through an electrolysis container in which the surface coating of the workpiece connected as cathode and the release of the coating material from the anode or from the electrolyte run,

- Through feed lines or openings for the electrolyte below in the space between the cathodically connected workpiece and the

Anode or at the bottom behind the anode,

by at least one overflow container adjoining or below the electrolysis container, into which the electrolyte arrives after passing through the electrolysis zone, and

- By means of a return conveyor with a filter, which enables both the circulation of the electrolyte and its cleaning of anode sludge as well as its supply to or through the anode, which is technically sufficiently controlled in terms of quantity, direction and speed.

The supply lines or openings for the electrolyte into the anode zone are particularly suitable, as their number, arrangement and throughput can be varied and optimized.

Either the bottom of the overflow container is designed as a settling cone with an emptying device - which settling cone can also have deflection plates and / or separating electrodes to improve the degree of separation - and / or it is in the line of the Return conveyor in the flow direction in front of the conveyor unit provided a filter that is cleaned continuously or periodically.

In the device specified above

- The cathodically connected object can either be fixed or movable, in particular rotatable, partially or completely immersed in the electrolyte located in the electrolysis container and

- The anode or the anode parts can also be immersed - likewise in the electrolyte - and optimally arranged with respect to their position in relation to the cathodically switched object.

The cathodically connected object can be a pressure cylinder for gravure printing, which is partially immersed in the electrolyte and is fixed or rotatable; the anode parts are then bowl-shaped and at a short distance from the pressure cylinder, the parts being porous or perforated. The supply lines or openings for the electrolyte to the electrolysis zone are those which, in terms of quantity, distribution, direction and speed, allow a technically sufficiently precisely controlled supply of the electrolyte to the zone mentioned.

Besides, also devices for the control and optimization of the method main parameters of the electrolyte such as throughput, temperature ^¬ tur, concentrations, etc. are important

The device according to the invention is used primarily for the production of gravure printing cylinders with a material structure of the surface coating that is free of foreign matter (especially sludge) and therefore finely crystalline, homogeneous and also corrosion-resistant.

In the following, both the execution according to the invention and the method carried out with it will be explained by way of example and in detail using the two figures belonging to the description of the invention. Show

- Figure 1 is a schematically illustrated according to the invention

Device with the overflow container and the adjoining the electrolysis container

- Figure 2 shows a corresponding device shown analogously with the overflow container arranged below the electrolysis tank.

In the device according to FIG. 1, the electrolysis container 1.01 with the electrolyte bath 1.02 is arranged centrally; of course, the actual dimensions of this container correspond to those of the workpiece to be coated. The anode or the anode parts 1.03 are set up in accordance with the cathodically connected workpiece 1.04. The electrolyte is brought to the corresponding outlet openings 1.06a, 1.06b and 1.07a, 1.07b by means of the two feed lines 1.05a, 1.05b. The two outlet openings 1.07a, 1.07b are designed and directed in such a way that a large part of the electrolyte conveyed reaches the space below between the anode parts 1.03 and the cathodically connected workpiece 1.04 and from there upwards and partly through the anode parts - flows: This is indicated in the figure by the arrows. A smaller part of the electrolyte exits into the electrolyte bath at the openings 1.06a, 1.06 and from there moves upwards on the side of the anode facing away from the cathode. These two directed flows effect an optimal removal and a sufficiently safe removal of most of the anode sludge which forms when the anode is dissolved.

Together with the circulating electrolyte, the anode sludge emerges from the electrolysis tank into the overflow tanks 1.08a, 1.08b arranged next to the said tank. If the electrolyte tank 1.02 is a longer tub, the two connected overflow tanks 1.08a, 1.08b are narrow side tubs. From the barrel containers 1.08a, 1.08b the liquid electrolyte runs through the lines 1.09a, 1.09b to the delivery units 1.10a, 1.10b, which the medium via the filters 1.11a, 1.11b again through the lines 1.05a, 1.05b the above the described outlet openings.

The two overflow containers 1.08a, 1.08b (they can together form a circulating, closed collecting container) can have individual or a coherent settling cone 1.12a, 1.12b with a corresponding drain line at the bottom.

FIG. 2 shows the corresponding device with the overflow container 2.08 arranged under the electrolysis container 2.01. The latter container also has a settling cylinder 2.12 with an emptying line.

The auxiliary devices for checking and optimizing the operating parameters for the electrolyte are not shown in both figures.

Only by actively removing the anode sludge at the point of origin and passively separating it from the electrolyte cycle is the effect to be achieved in accordance with the invention fully achieved. It is clear to the person skilled in the art that the practical means given in these examples for active and passive anode electrode removal can also be replaced by other, effect-analogous elements.

Claims

PATENT CLAIMS

1. Method for the electrolytic surface coating of the electrical current-conducting, in particular of metal workpieces, by means of a fluid electrolyte, d a d u r c h g e k e n n z e i c h n e t,

- That the electrolyte is conveyed in a controlled circulation in and around the electrolysis zone between the anode and the cathodically switched workpiece, the electrolyte for the most part at a high throughput rate, possibly under a higher inlet pressure, through the space between the cathodically switched workpiece and the anode and, to a lesser extent, are conveyed upwards at a lower throughput rate on the rear side of the anode facing away from the cathode,

anode sludge being separated or separated from the electrolyte in the overflow tank and / or in the return device. 2. The method according to claim 1, further characterized in that the electrolyte is brought up to the anode, through the anode or is removed from the anode in such a way that the major part of the anode sludge which forms during the electrolysis is carried away by the flowing electrolyte.

3. The method according to claim 1 and / or 2, so that the electrolyte on the circulation is continuously checked with regard to the essential process parameters such as temperature, conversion, contents etc. and, if necessary, optimized.

4. The method according to claim 3, w e i t e r d a d u r c h g e k e n n z e i c h n e t that the cathodically connected workpiece is either fixed or moved, in particular rotated during the electrolytic surface coating, and that the anode is either replaced periodically or the anode material is continuously updated.

5. The method according to any one of claims 1 to 4, characterized in that the anode sludge is separated or separated from the electrolyte during its passage through the overflow tank either by settling and / or by means of electrodes and / or by the sludge particles a filter switched on in the return device are retained.

6. Device for the electrolytic surface coating of the electrical current-conducting, in particular metal workpieces, by means of a fluid electrolyte by an electrolysis container (1.01) in which the surface coating of the workpiece (1.04) connected as cathode and the delivery of the coating material from the anode (1.03) or from the electrolyte run,

d u r c h supply lines (1.05) or openings (1.06, 1.07) for the electrolyte below into the space between the cathodically connected workpiece (1.04) and the anode (1.03) or below behind the anode,

10 d u r c h at least one overflow tank (1.08, 2.08) adjoining or under the electrolysis tank, into which the electrolyte gets after passing through the electrolysis zone, and

15

- By means of a return conveyor with a filter (1.11), which enables both the circulation of the electrolyte and its cleaning of anode sludge as well as its supply ^{'20 which is} technically sufficiently controlled in terms of quantity, direction and speed to and through the anode.

7. The device according to claim 6, w e i t e r d a d u r c h g e k e n n z e i c h n e t that the supply lines (1.05) or 25 openings (1.06, 1.07) for the electrolyte in the anode zone in their number, arrangement and throughput are variable and can be optimized.

30 ___ Device according to claim 7, characterized in that either the bottom of the overflow container is designed as a settling cone (1.12, 2.12) with an emptying device, which settling cone can also have deflection plates and / or separating electrodes for improving the degree of separation, and that in the

35 line of the return device in the flow direction before Conveying unit (1.10) a filter (1.11) is provided, which is cleaned continuously or periodically.

9 ^ Device according to claims 7 and 8, w e i t e r d a d u r c h g e k e n n z e i c h n e t,

- That the cathodically connected object (1.04) is either fixed or movable, in particular rotatable, partially or completely immersed in the electrolyte located in the electrolysis container (1.02) and

- That the anode or the anode parts (1.03) are also immersed in the electrolyte (1.02) and are optimally arranged with respect to their position in relation to the cathodically connected object (1.04).

10. Device according to one of the claims 6 to 9, further characterized in that the cathodically connected object (1.04) is a printing cylinder for gravure printing, which is partially immersed in the electrolyte (1.02) and is fixed or rotatably arranged, that the anode parts (1.03) are cup-shaped and at a short distance from the pressure cylinder, the parts can be porous or perforated, and that the supply lines (1.05) or openings (1.06, 1.07) for the electrolyte to the electrolysis zone in terms of quantity , Distribution, direction and speed allow technically sufficiently precisely controlled feeding of the electrolyte into the named zone.

11. Device according to one of claims 6 to 9, further characterized by devices for checking and optimizing the main process parameters of the electrolyte such as throughput, temperature, concentrations, etc. 12. Use of the device according to one of the claims 6 to and 10 for the production of rotogravure cylinders by including foreign matter (especially sludge) free and therefore finely crystalline, homogeneous and also corrosion-resistant material structure of the surface coating.