EP3514263B1 - Method and device for electrolytic coating a metal strip - Google Patents

Description

technical field

The invention relates to a device and a method for the electrolytic treatment, in particular cleaning, of a metal strip which is transported along a transport direction through a treatment section of the device and is exposed to an electrolytic treatment liquid via a nozzle.

Background of the Invention

the DE 31 08 615 A1 describes an apparatus for the electrolytic treatment of a metal strip, in particular for the electrolytic plating or descaling of the surfaces of the metal strip.

For this purpose, the device has an electrolysis tank, in which there is an electrolytic liquid, and a number of rollers, which are arranged along a transport path of the metal strip. The metal strip is deflected in a zigzag fashion by the rollers and moves through the electrolysis tank. The apparatus further comprises paired electrode pads which are provided in parallel and face each other so that the metal strip for electrolytic treatment is transported vertically therebetween. Each electrode pad is provided with slits through which the electrolyte is discharged to the surface of the metal strip with a high static pressure. To achieve the electrolytic descaling or plating effect, a voltage is applied between the metal strip, for example by contacting an electrically conductive roller, and the electrode pads.

The electrode pads of the device set forth above are located outside the electrolytic bath. Alternatively, dip pole plates may be partially or substantially fully immersed in the electrolytic bath as described in FIG 1 the DE 31 08 615 A1 is shown. As it passes through the electrolyte, the metal strip is electroplated or electrolytically descaled by applying a voltage between the metal strip as the cathode and a dipped pole plate as the anode. Devices with an electrolytic bath and electrodes immersed in it are also known from JP H05 195300 A , JP H11 286185 A and JP 2004 268517A known.

Another device for electrolytic treatment, such as cleaning, a metal strip is from DE 102 12 436 A1 out. Here, too, the treatment of the metal strip takes place during vertical transport through a treatment area.

Furthermore, horizontal systems are known which carry out the electrolytic treatment on the metal strip running horizontally. That's how she describes it DE 102 10 538 B4 the electrolytic treatment, metallization and etching of items to be treated, for example printed circuit boards, in a horizontal continuous system. A device of similar design is from JP 2011 246790 A known.

the EP 0 870 854 B1 describes a device for the electrolytic cleaning of a metal strip. Here, the metal strip to be cleaned is passed horizontally between opposite, facing nozzles. The nozzles spray an alkaline aqueous solution on both sides of the strip, with one of the nozzles being a positive electrode and the other nozzle being a negative electrode. After this, the metal strip is brushed in a jet of clean water with brush rollers placed at positions in the direction of transport of the strip next to the nozzles.

The energy requirement for the electrolytic treatment of a metal strip is high.

In addition, the maintenance of such a system is expensive.

Presentation of the invention

An object of the invention is to provide an improved device and an improved method for the electrolytic treatment, preferably cleaning, of a metal strip.

The object is achieved with a device having the features of claim 1 and a method having the features of claim 9. Advantageous developments follow from the dependent claims, the following description of the invention and the description of preferred exemplary embodiments.

The device according to the invention is used for the electrolytic treatment of a metal strip using an electrolytic treatment liquid. For treatment, the metal strip is transported along a transport direction through a treatment section. The metal strip can be transported, for example, by means of rollers. Preferably, the device and the method set forth below are used for the electrolytic cleaning of the metal strip by means of an electrolytic cleaning liquid. “Cleaning” is understood here as meaning in particular the removal of surface coatings such as metal particles (Fe/Al fines), oil and grease contamination, anti-corrosion oils, lubricating oils and/or deep-drawing aids that reduce the coefficient of friction.

The device has at least one surge nozzle, which has a surge opening and an electrode, with at least two surge nozzles being present according to the invention. The gush nozzle is configured to bring an electrolytic treatment liquid, which is preferably an alkaline solution, into contact with the electrode, discharge it from the gush opening, and apply it to at least one surface of the metal strip in the treatment section. The treatment liquid is preferably applied to the metal strip at a low pressure, for example less than 100 mbar. The device also has a Power supply that is set up to apply an AC voltage between the metal strip and the electrode.

High current densities can be achieved on the metal strip to be treated by the alternating voltage applied in conjunction with a surge nozzle. This leads to increased activity of the treatment liquid due to stronger turbulence and better mixing. At the same time, the treatment liquid acts on a thin boundary layer in the transition between the treatment liquid and the strip surface, as a result of which the electrical current losses can be reduced. In this way, the specific energy consumption can be reduced. The technical effects are supported by the surge-like dispensing of the treatment liquid, i.e. the dispensing of the treatment liquid at a pressure that is preferably low in comparison to high-pressure nozzles. In addition, due to the reduced stray current, the corrosion tendency on metallic parts of the device is reduced. In addition, conventional dip pole plates or high-pressure nozzles can be dispensed with, which means that the maintenance and, if necessary, the replacement of such components is no longer necessary. This not only achieves a further reduction in energy consumption and maintenance costs, but also optimizes the availability of the device. The assembly and disassembly of conventional immersion pole plates is complicated. In contrast, the surge nozzle can be easily decoupled from the cleaning tank, particularly when using flange plates. In this way, the surge nozzle can be removed from the side of the cleaning tank and installed in it for maintenance and repair work without dismantling other tank installations. Due to electrolytic erosion and alkaline attack by the treatment liquid, the electrodes of the surge nozzles (similar to the dip pole plates) are wear components that require replacement and maintenance at regular intervals for safety and process reasons.

According to the invention, the device has at least two, particularly preferably exactly two, surge nozzles, which are arranged in pairs, so that the treatment section is located between two surge nozzles arranged in pairs. In this case, each surge nozzle has a surge opening and an electrode further arranged to bring the electrolytic treatment liquid into contact with the electrode, discharge it from the associated surge port, and apply it to at least one surface of the metal strip in the treatment section. The surge openings of two surge nozzles arranged in pairs face one another here, so that the metal strip passing through the treatment section can be subjected to treatment liquid on both sides. Furthermore, according to this embodiment, the power supply is set up to apply an AC voltage between the metal strip and the electrodes of each of the surge nozzles.

The above preferred embodiment enables the metal strip to be treated on both sides and in particular uniformly. For this purpose, the electrodes of the surge nozzles arranged in pairs are preferably contacted symmetrically to the fluid flow.

The device is preferably set up in such a way that the metal strip passes essentially vertically through the treatment section. In this context, vertical means in the direction of gravity, as a result of which the treatment liquid can run off along the belt in a manner defined in terms of time and space. There is therefore no need to remove the treatment liquid using brushes, compressed air, etc. This leads to a further optimization of the energy consumption and maintenance effort of the device.

The surge nozzle preferably has an elongate base body with at least one outlet opening, which is preferably designed as a slit along the longitudinal extension of the base body, with the electrode being attached to the outside of the base body in such a way that it overlaps the outlet opening in such a way that the treatment liquid emerging from the outlet opening with comes into contact with the electrode. In this way, the treatment liquid can be subjected to alternating voltage by a constructively simple and reliable surge nozzle. The electrode and the body are preferably releasably connected to each other to easily change the configuration of the surge nozzle and adapt it to the treatment environment to be able to adapt. The base body is also preferably made of one or more non-conductive materials, such as plastic.

The electrode preferably has two electrode sections, each of which has a longitudinal edge which faces one another in such a way that they form a slit-shaped outlet opening. For this purpose, the electrode sections are preferably two independent components, which can be of the same, symmetrical or modular design. In this way, the contact surface of the electrode, i.e. the surface that comes into electrical contact with the treatment liquid, can be adjusted and optimized in a simple manner. The contact surface can be adjusted manually or automatically by one or more actuators, which means that the treatment effect, energy consumption, etc. can be optimized without dismantling the surge nozzle, for example during operation of the device.

The electrode sections are preferably built into the surge nozzle as operational interchangeable parts and are therefore designed for quick and uncomplicated disassembly and assembly. This not only improves the regular maintenance of the surge nozzle, but also allows the electrode sections to be changed to known or newly developed materials with optimized properties, for example with regard to service life and/or electrical properties, with low material and personnel costs.

Preferably, the surge nozzle also has at least one nozzle plate, which forms the surge opening and is attached to the outside of the base body in such a way that the electrode is located between the base body and the nozzle plate. Preferably, the surge nozzle has two nozzle plates, each having a nozzle lip facing each other, so that the surge opening is formed in a slit-like manner between the nozzle lips. Furthermore, the nozzle plates can have slots, for example, via which the nozzle plates are adjustably attached to the base body and/or the electrode by means of screws. Such a sandwich-like and possibly multi-part arrangement offers a large number of setting options with regard to the discharge characteristics and electrical contacting of the treatment liquid. at the same time reliable and low-maintenance design of the surge nozzle.

The surge nozzle is preferably held rotatably about its longitudinal axis, as a result of which the angle of flow of the treatment liquid to the metal strip can be adjusted. This represents another degree of freedom to optimize the treatment effect, energy consumption, etc.

The electrode sections preferably each have a connection section, via which they are each electrically contacted. If the electrode sections are stamped out of sheet metal, for example, the connection sections can be formed, for example, by bending over a sheet metal section. According to this exemplary embodiment, the electrode sections arranged in pairs each have one, i.e. a total of two, connection sections. The positions of the two connecting sections are preferably selected in such a way that the most homogeneous possible treatment result is achieved. This is achieved in particular when the two connection sections are arranged on opposite sides of the electrode sections, viewed along the longitudinal extension of the surge nozzle. In this case, any electrical interference and influencing variables are compensated.

The design variants of the gush nozzle presented above apply analogously to the case of multiple gush nozzles.

The method according to the invention is also used for the electrolytic treatment, preferably cleaning, of a metal strip that is transported along a transport direction through the treatment section. The method is carried out using a device according to one of the embodiment variants presented above and has: contacting an electrolytic treatment liquid with the electrode of each of the surge nozzles, with an alternating voltage being applied between the electrode and the metal strip; discharging the treatment liquid from the surge port of each of the surge nozzles; and applying the treatment liquid to a corresponding surface of the treatment section in the treatment section Metal strip, so that the metal strip (B) passing through the treatment section is treated on both sides with treatment liquid.

The features, technical effects, advantages and exemplary embodiments that have been described in relation to the device apply analogously to the method.

Although the devices and methods presented above can be used with particular preference in electrolytic cleaning lines for strip systems, they can also be used for a different treatment of metal strips, provided that electrolytic wetting of strip surfaces is included. The devices and methods presented above form an improved technique for substituting dip pole plates and/or electrolytically acting high-pressure cleaning nozzles. Conventional systems can thus be retrofitted in a particularly cost-effective and structurally simple manner.

Further advantages and features of the present invention can be seen from the following description of preferred exemplary embodiments. The features described there can be implemented on their own or in combination with one or more of the features set out above, insofar as the features do not contradict one another. The following description of the preferred embodiments is made with reference to the accompanying drawings.

Short description of the figures

• the figure 1 shows schematically the principle of an improved electrolytic cleaning device compared to a conventional principle.
• the figure 2 is a three-dimensional representation of a surge nozzle and its mounting.
• the figure 3 shows a detail of the mounting of two surge nozzles, which are arranged facing each other.
• the figure 4 Figure 13 is a three-dimensional sectional view of a surge nozzle.
• the figure 5 Fig. 12 is a schematic three-dimensional view showing the structure of a surge nozzle in an exploded manner.
• the figure 6 is a three-dimensional representation of a surge nozzle without nozzle plates, which shows the structure and the position of the electrodes.

Detailed description of preferred embodiments

Preferred exemplary embodiments are described below with reference to the figures. The same, similar or equivalent elements are provided with identical reference symbols. A repeated description of these elements is also partially dispensed with in order to avoid redundancies.

the figure 1 shows a device 1, which is specially designed for cleaning a metal strip B here.

The device 1 has a plurality of rollers 2 over which the metal strip B is transported in a zigzag fashion along a transport direction T. The device 1 has two surge nozzles 10 between which the metal strip B passes and facing each other in a manner (described in detail below) such that both surfaces of the metal strip B can be contacted with an aqueous electrolyte. The metal strip B runs through the space between the two surge nozzles 10, preferably vertically, in the descending transport direction. Alternatively or additionally using further surge nozzles, the metal strip B can also pass these in the ascending direction of transport.

For electrolytic cleaning, an alternating voltage is applied between the metal strip B and the electrodes (described in detail below) of the surge nozzles 10 . For this purpose, the device 1 has a power supply 3 which is set up to provide and apply the AC voltage. For this purpose, the power supply is electrically connected to the electrodes of the surge nozzles 10 and the metal strip B, for example via a conductive roller 2 .

The electrolyte, which is a cleaning liquid or cleaning solution, is an alkaline solution, for example.

It should be noted that in the figure 1 shown form of transport is not absolutely necessary, in particular can be dispensed with repeated deflection of the metal strip B over rollers 2, since the improved cleaning principle does not require several pairs of dip pole plates arranged in the figure 1 are denoted by the reference P. According to a conventional principle, the dip pole plates P are immersed in an electrolyte bath in order to achieve an electrolytic cleaning effect when a voltage is applied between the dip pole plates P and the metal strip B. The partial representation of this conventional principle in the figure 1 serves to show the retrofitting of a conventional system. The conventional transport path of the metal strip B can thus be retained. Likewise, the conventional dipping pole plates P and/or other components of the conventional system do not necessarily have to be dismantled, which means that conversion costs can be saved. However, the dipping pole plates P are deactivated, and an electrolyte bath is also dispensed with, since the cleaning is carried out solely by the surge nozzles 10 .

the figure 2 shows in perspective such a surge nozzle 10 and its suspension or storage.

The surge nozzle 10 has an elongate, for example cuboid, base body 20 . Inside, the base body 20 has one or more channels through which an electrolyte, supplied via tubes 11, flows and is distributed along the longitudinal extent of the surge nozzle 10. In the simplest case, the base body 20 is hollow, as can be seen from the Figures 4 and 5 emerges. The base body 20 has one or more outlet openings 21 (cf. figure 4 ) through which the electrolyte can escape laterally from the base body 20. The base body 20 is made of a non-conductive material, preferably plastic.

The surge nozzle 10 also has a surge opening 30, which is preferably a slit. The surge opening 30 can be formed by two nozzle plates 31 each having an elongated nozzle lip 32 facing each other, as in FIG figure 2 shown. The nozzle plates 31 are fastened to the base body 20 in such a way that the electrolyte exiting via the outlet opening 21 is discharged to the outside through the surge opening 30 . The two nozzle plates 31 are preferably designed to be adjustable, for example by being fitted with slotted holes 33 and corresponding screws 34 (cf. figure 5 ) are connected to the base body 20 and can be moved in such a way that the distance between the two nozzle lips 32, and thus the slot width, is adjustable. The nozzle plates 31 are made of a non-conductive material, preferably plastic. Due to their shape, the nozzle lips 32 decisively determine the shape or nature of the surge of electrolyte emerging through the nozzle opening 30 . For this reason, the nozzle plates 31 with their nozzle lips 32 are preferably provided to be exchangeable.

An electrode 40 is provided between the base body 20 and the nozzle plates 31, which electrode has two electrode sections 40a and 40b in the present example. The position of the electrode sections 40a, 40b is particularly clear from the figure 5 and is described in detail below. First of all, it should only be pointed out that the liquid electrolyte, before it emerges from the surge opening 30, comes into contact with the electrode sections 40a, 40b. For electrolytic cleaning, an AC voltage is applied between the electrode sections 40a, 40b and the metal strip B, which results in an ion current in the electrolyte, as a result of which the electrolytic cleaning effect on the surfaces of the metal strip B is achieved.

the figure 2 shows an exemplary suspension or mounting of the same next to the surge nozzle 10 . For this purpose, the tubes 11 , which are connected to the base body 20 on both sides (seen in the longitudinal direction), are held in a storage device 50 . the figure 3 shows an enlarged detail of the storage device 50, wherein two surge nozzles 10 are arranged with their surge openings 30 facing each other.

The surge nozzles 10 are mounted such that they can be rotated or adjusted about their longitudinal axes, in that the tubes 11 are held, for example, by a detachable clamp 51 each. Of course, the storage can also be realized in other ways. In particular, the adjustability of the surge nozzle 10 or parts thereof along one or more degrees of freedom can be realized automatically by means of actuators (such as electric, magnetic, hydraulic, pneumatic, etc.). This also applies, for example, to the adjustability of the nozzle plates 31.

The storage device 50 can have a screwable flange plate (no reference number), whereby the surge nozzle 10 in a simple manner from Cleaning tank can be decoupled. In this way, the surge nozzle 10 can be removed from the side of the cleaning tank for maintenance and repair work without dismantling other tank installations. Conventional taupole plates P can only be removed via the top space of the cleaning tank and thus require a time-consuming dismantling of the existing tank installations in the top space.

the Figures 4 and 5 12 are three-dimensional sectional views of an exemplary surge nozzle 10, with the section being taken perpendicular to the longitudinal axis. In the figure 5 the components are shown partially exploded.

From the figure 5 the sandwich-like arrangement of the electrode sections 40a, 40b, which are provided between the base body 20 and the nozzle plates 31, emerges particularly clearly. The electrode sections 40a, 40b extend essentially over the entire length of the base body 20 and are located on the side of the outlet opening 21. The electrode sections 40a, 40b also form an outlet opening 41 through which the electrolyte is discharged to the surge opening 30 and then to the outside . In the present example, the electrode sections 40a, 40b each have a longitudinal edge 42a, 42b, which run parallel and form the outlet opening 41 as a slit. It should be pointed out that the electrode sections 40a, 40b can also be designed in a different way, for example as a one-piece electrode. It is important that the electrode sections 40a, 40b overlap the exit opening 21 of the base body 20 in such a way that the electrolyte comes into contact with them when exiting. In the present exemplary embodiment, the longitudinal edges 42a, 42b protrude beyond the corresponding longitudinal edges 21a, 21b of the outlet opening 21. In other words, the slit-like exit opening 21 of the base body 20 is narrower than the slit-like exit opening 41 formed by the two electrode sections 40a, 40b.

The overlap distance d, which denotes the distance between the longitudinal edge 42a of the electrode section 40a and the associated longitudinal edge 21a of the outlet opening 21 (analogous to longitudinal edges 42b and 21b) in the plane of the electrode 40, is in the range of 10 to 30 mm, for example, specifically approximately at 20mm. The slit-like surge opening 30 coincides with the outlet opening 41 or is narrower than this. The distance s between the nozzle lips 32 is preferably in the range from 2 to 6 mm, as a result of which a surge of electrolyte with a relatively low pressure can be achieved. The base body 20 can have a length of approximately 1,200 mm, for example. In this case, the contact area of the electrode 40, ie the area that comes into contact with the electrolyte when it exits, is approximately 24,200 mm ² with an overlap distance of d=20 mm.

The nozzle lips 32 can be shaped differently for the direction and shape of the electrolyte surge, as can be seen from the figure section 5(I).

The electrode sections 40a, 40b can each be stamped out of sheet metal and each have a connection section 43a and 43b, via which the electrode sections 40a, 40b are electrically contacted. The connection section 43a, 43b can be formed, for example, by bending over a sheet metal section of the electrode sections 40a, 40b and can have an opening for a screw connection.

The positions of the two connecting sections 43a, 43b are preferably chosen in such a way that the most homogeneous possible treatment result is achieved. In the present exemplary embodiment, this is achieved in that the two connection sections 43a, 43b are arranged on opposite sides of the electrode sections 40a, 40b, viewed along the longitudinal extent of the surge nozzle 10. In this case, any electrical interference and influencing variables are compensated.

The position and nature of the electrode sections 40a, 40b relative to the base body 20 is particularly clear from the three-dimensional representation of figure 6 emerges, in which the nozzle plates 31 are omitted.

The surge nozzle 10, in particular its surge opening 30, is designed in such a way that the electrolyte can be discharged with a low pressure in comparison to conventional high-pressure nozzles. The electrolyte is brought into contact with the metal strip B as a gush. For example, the electrolyte has a pressure of less than 100 mbar. Furthermore, an AC voltage is applied between the electrode sections 40a, 40b and the metal strip B, whereby not only a uniform cleaning of both sides of the metal strip B but also the electrolytic cleaning effect is achieved with a comparatively low energy consumption. The two-sided cleaning is preferably carried out simultaneously and at the same "place", i.e. there is no local and no time offset in the cleaning activities of the two sides of the belt. This contributes to a homogeneous cleaning result.

The surge nozzles 10 presented here are particularly preferred for use in electrolytic cleaning lines for strip systems. They form an improved technique for substituting dip pole plates P and/or electrolytically acting high-pressure cleaning nozzles. “Cleaning” is understood here to mean in particular the removal of surface coatings such as metal particles (Fe/Al fines), oil and grease contamination, anti-corrosion oils, lubricating oils and/or deep-drawing aids that reduce the coefficient of friction.

High current densities can be achieved on the metal strip B to be treated as a result of the surge-like ejection of the electrolyte, ie the ejection of the electrolyte at a pressure which is low in comparison with conventional high-pressure nozzles. For example, the current at the electrode sections 40a, 40b is approximately 800 A with an applied voltage of approximately 20 V. This leads to a increased activity of the cleaning solution due to stronger turbulence and better mixing. At the same time, the cleaning solution acts on a comparatively thin boundary layer in the transition between the cleaning solution and the strip surface, as a result of which the electrical current losses can be reduced. In connection with the use of AC voltage instead of DC voltage, the specific energy consumption can be reduced.

As far as applicable, all individual features that are presented in the exemplary embodiments can be combined with one another and/or exchanged without departing from the scope of the invention.

Reference List

1

contraption

2

role

3

power supply

10

surge nozzle

11

Pipe

20

body

21

exit port

21a

long edge

21b

long edge

30

surge port

31

nozzle plate

32

nozzle lip

33

Long hole

34

screw

40

electrode

40a

electrode section

40b

electrode section

41

exit port

42a

long edge

42b

long edge

43a

connector section

43b

connector section

50

storage device

51

clamp

B

metal strap

T

Transport direction of the metal strip

P

plunger plate

i.e

overlap distance

s

slot width of the surge opening

Claims (12)

1. Device (1) for electrolytic treatment, preferably cleaning, of a metal strip (B), which is transportable along a transport direction (T) through a treatment section of the device (1), wherein the device (1) comprises:

   at least two surge nozzles (10) which are arranged in paired manner so that the treatment section is present between two surge nozzles (10) arranged in paired manner, wherein each of the surge nozzles (10) has a surge opening (30) and an electrode (40), further arranged so as to bring an electrolytic treatment liquid into contact with the corresponding electrode (40), to deliver it from the corresponding surge opening (30) and to apply it in the treatment section to at least one surface of the metal strip (B), and

   the surge openings (30) of two surge nozzles (10) arranged in paired manner face one another so that the metal strip (B) passing through the treatment section can be acted on at both sides with treatment liquid,

   characterised by

   a power supply (3) which is arranged to apply an alternating voltage between the metal strip (B) and the electrode (40) of each of the surge nozzles (10).
2. Device (1) according to claim 1, characterised in that this is so oriented that the metal strip (B) passes vertically through the treatment section.
3. Device (1) according to one of the preceding claims, characterised in that each of the surge nozzles (10) comprises an elongate base body (20) with at least one outlet opening (21), preferably formed as a slot along the length direction of the base body (20), wherein the electrode (40) is so mounted externally on the base body (20) that this overlaps the outlet opening (21) in such a way that the treatment liquid issuing from the outlet opening (21) comes into contact with the electrode (40).
4. Device (1) according to claim 3, characterised in that the electrode (40) has two electrode sections (40a, 40b) each having a respective longitudinal edge (42a, 43b), the longitudinal edges so facing one another that they form a slot-shaped outlet opening (41).
5. Device (1) according to claim 4, characterised in that the electrode sections (40a, 40b) each have a connecting section (43a, 43b) for electrical contact-making, wherein the two connecting sections (43a, 43b) are arranged at opposite sides of the electrode sections (40a, 40b) as seen along the length direction of the surge nozzle (10).
6. Device (1) according to any one of claims 3 to 5, characterised in that each of the surge nozzles (10) further comprises at least one nozzle plate (31) which forms the surge opening (30) and is so mounted externally on the base body (20) that the electrode (40) is between the base body (20) and the nozzle plate (31).
7. Device (1) according to claim 6, characterised in that each of the surge nozzles (10) comprises two nozzle plates (31) each having a respective nozzle lip (32), the nozzle lips facing one another so that the surge opening (30) is formed in slot-like manner between the nozzle lips (32), wherein the nozzle plates (31) preferably have slots (33) by way of which the nozzle plates (31) are adjustably mounted on the base body (20) and/or the electrode (40) by means of screws (34).
8. Device (1) according to any one of the preceding claims, characterised in that each of the surge nozzles (10) is mounted to be rotatable about the longitudinal axis thereof.
9. Method for electrolytic treatment, preferably cleaning, of a metal strip (B) which is transported along a transport direction (T) through a treatment section, wherein the method is performed by a device (1) according to any one of claims 1 to 9 and comprises:

   contacting an electrolytic treatment liquid with the electrode (40) of each of the surge nozzles (10);

   delivering the treatment liquid from the surge opening (30) of each of the surge nozzles (10); and

   applying the treatment liquid in the treatment section to a corresponding surface of the metal strip (B) so that the metal strip (B) passing through the treatment section is acted on at both sides by the treatment liquid,

   characterised in that

   an alternating voltage is applied between the electrode (40) and the metal strip (B).
10. Method according to claim 9, characterised in that the metal strip (B) is transported vertically through the treatment section.
11. Method according to claim 9 or 10, characterised in that the treatment liquid is applied to the metal strip (B) at a pressure of less than 100 mbar.
12. Method according to any one of claims 9 to 11, characterised in that the treatment liquid is an alkaline solution.

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