CN114207190A

CN114207190A - Method and device for electrolytically coating electrically conductive strips and/or fabrics by means of impulse technology

Info

Publication number: CN114207190A
Application number: CN202080054400.4A
Authority: CN
Inventors: H·戈尔茨; T·道贝; F·普拉特; W·蒂默博伊尔
Original assignee: SMS Group GmbH
Current assignee: SMS Group GmbH
Priority date: 2019-08-05
Filing date: 2020-08-05
Publication date: 2022-03-18
Also published as: CN114174559A; CN114174560A; EP4010516A1; WO2021023779A1; WO2021023789A1; EP4010515A1; CN114207191A; US20220275530A1; EP4010518A1; EP4010517A1; WO2021023783A1; WO2021023778A1

Abstract

The invention relates to an electroplating method and device for electrolytically coating an electrically conductive strip and/or an electrically conductive band fabric, preferably a metal strip, a plastic strip, a glass fiber fabric strip, a carbon fiber woven fabric strip and/or a composite thereof, for example a steel strip, with a coating based on a metal and/or semimetal selected from groups 6 to 15 and/or mixtures thereof by means of a pulse technique.

Description

Method and device for electrolytically coating electrically conductive strips and/or fabrics by means of impulse technology

Technical Field

The invention relates to an electroplating method and device for electrolytically coating electrically conductive strips and/or electrically conductive band fabrics, preferably metal strips (e.g. steel strips), plastic strips, glass fiber fabric strips, carbon fiber woven fabric strips and/or composites thereof, with a coating based on a metal and/or semimetal selected from groups 6 to 15 and/or mixtures thereof.

Background

Electrolytically refined strip, for example steel strip, is nowadays used as a semifinished product in many branches of industry, for example in the automotive industry, aerospace technology, mechanical engineering, packaging industry and in the manufacture of household and electrical appliances. Strips of this type are conventionally produced in continuously operating strip processing plants, in which the strip is passed at a constant speed through one or more electrolytic cells connected in succession.

The coating electrolytically deposited on one or both sides of the strip can here assume various tasks and give the corresponding strip new product properties. They are, for example, corrosion protection or oxidation protection, wear protection, production of decorative product properties and/or production of magnetic and/or electrical surface properties.

Thus, electrolytically galvanized steel strips are effectively protected against corrosion, for example by a zinc coating, and provide a good adhesion base for lacquers and/or for coating by plastic films. The chromium coating likewise imparts enhanced corrosion and wear protection to the steel or plastic strip, and also imparts decorative properties. Nickel and nickel alloys, on the other hand, can increase the surface hardness of the corresponding substrates.

The production of corresponding coatings with the desired properties is highly dependent, in particular economically and economically, on various parameters, such as the type and composition of the electrolyte, the concentration and temperature of its metal salts, the geometrical arrangement of the electrolytic cell and its electrodes, the guidance of the electrochemical current and its value, time and polarity.

In the prior art, the electrolytic coating of metal strips is carried out by means of direct current, wherein thyristor technology is used here. The so-called direct current electrolysis can be designed unipolar and with partially reversed polarity, however, specific current sequences in terms of value, time and polarity are not permitted.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved method and an improved device for the electrolytic coating of electrically conductive strips and/or electrically conductive webs with a coating based on metals and/or semimetals selected from groups 6 to 15 and/or mixtures thereof, compared to the prior art.

According to the invention, this object is achieved by a method having the features of claim 1 and by an apparatus having the features of claim 12.

In the method according to the invention, it is provided that after necessary prior cleaning and/or activation, an electrically conductive strip and/or an electrically conductive web (preferably a metal strip, a plastic strip, a glass fiber fabric strip, a carbon fiber woven fabric strip and/or a composite thereof) is fed to a coating station and continuously electrolytically coated in the coating station, the coating station comprising at least one, preferably at least two or more electrolytic cells, wherein the electrically conductive strip and/or web is first connected to a cathode by means of at least one electrically conductive roller and is guided in the at least one electrolytic cell at a defined distance parallel to at least one anode arranged in the electrolytic cell.

According to the invention, the at least one anode is energized by means of a modulated current, wherein the coating process takes place within the coating section using a defined pulse waveform sequence, which is formed by at least one pulse waveform, wherein at least one metal selected from the group 6 to 15 metals and/or at least one semimetal selected from the semimetals and/or mixtures thereof is deposited from an electrolyte onto the electrically conductive strip and/or the band fabric and a coating is formed.

The invention also relates to a device for electrolytically coating an electrically conductive strip and/or an electrically conductive web. The apparatus comprises: optionally a cleaning and/or activation unit in which the electrically conductive strip and/or fabric can be cleaned and/or activated; a coating section having at least one, preferably at least two or more electrolytic cells in which the electrically conductive strip and/or fabric can be continuously electrolytically coated; and at least one electrically conductive roller, by means of which the electrically conductive strip and/or the band fabric can be connected to the cathode, wherein the at least one electrolytic cell comprises at least one anode which is arranged such that the electrically conductive strip and/or the band fabric guidable through the at least one electrolytic cell can be guided at a defined and parallel spacing relative to the at least one anode. According to the invention, the device comprises at least one pulse rectifier, which is implemented in a switched-mode power supply technology, the negative pole of which is electrically connected to the at least one electrically conductive roller and the positive pole of which is electrically connected to the at least one anode, so that the at least one anode can be energized by means of a modulated current, so that the coating process can be carried out within the coating section using a defined pulse waveform sequence, wherein the pulse waveform sequence is formed by individual pulse waveforms, wherein at least one metal from the group 6 to 15 metals and/or at least one semimetal from the semimetals and/or mixtures thereof can be deposited from an electrolyte onto the electrically conductive strip and/or band fabric according to the pulse waveform sequence.

The use of a pulse rectifier makes it possible to define the number, the time profile and the polarity of the respective desired pulse shape and thus of the entire pulse shape sequence, so that the electrolysis process can be optimally adapted to the respective system according to predetermined parameters. For this purpose, according to the invention, it is provided that the coating process is carried out within the coating section using a defined pulse shape sequence, which is formed by the individual pulse shapes. In this case, the pulse shape sequence can be formed by a single pulse shape and/or by a combination of at least two or more identical and/or different pulse shapes from the pulse shape set.

Thus, changing the polarity can, for example, reverse the deposition process. By changing the polarity, for example, it is possible to modify regions of the (partially) coated substrate which, during a preceding cathodic coating step and/or coating process, have an excessively high layer thickness or dendritic crystal growth relative to the remaining regions, for example due to a high current density at the edge of the substrate. Thus, changing the polarity, i.e. the anode operation, makes it possible to specifically reduce local overshoots and to equalize the layer thickness in this region with the surrounding region.

Furthermore, the electrolysis process can be designed using modulated current in such a way that particularly compact, clean, homogeneous, finely crystalline, pore-free, crack-free and dendrite-free coatings can be achieved. Furthermore, the electrically conductive strip and/or the band fabric to be coated can be coated with a uniform layer thickness over its entire surface in a continuous coating process, which extends uniformly, in particular over the strip width (edge effect), and which has no local over-coating and/or under-coating. The complicated use of an edge mask can thus advantageously be dispensed with.

Furthermore, the use of modulated current in bipolar operation results in a multilayer composition with improved properties. By selecting the pulse shape, the nucleation, its number and the distribution on the electrically conductive strip and/or the band can be influenced in a targeted manner, which leads to advantageous crystal growth. The Nernst diffusion layer can also be split by the repeated pulse shape, which leads to an improved material transport behavior at the cathode, i.e. the electrically conductive strip and/or band connected to the cathode, and shows a deposition of a coating with a lower roughness, an increase in its gloss, and a denser coating and thus an increase in the corrosion resistance.

By forming a leading pulse (vorimapple) that is short in time but numerically higher than the average current density, a greater number of metal ions and/or semimetal ions can be transported to the strip and/or band connected to the cathode, which causes a finer grained morphology of the coating and suppresses possible subsequent reactions at the cathode, such as the production of hydrogen, by the high current pulse. This is simultaneously associated with an increased efficiency of the deposition process or a higher current efficiency.

The generation of large amounts of hydrogen has proven to be particularly problematic in the electrolytic coating processes known from the prior art, since the hydrogen diffusing into the metal strip has a great negative effect on the product properties of the metal strip in the subsequent production steps. The diffused hydrogen mainly causes so-called spontaneous brittle fracture of the metal strip, in particular steel strip, and a reduction in the material yield limit or the required strength. Furthermore, hydrogen gas trapped in the coated steel strip, in particular in the case of galvanized steel strips, can lead to the release of trapped hydrogen during the curing of the coated parts, with the result that hydrogen bubbles form below the coating layer, which leads to what is known as "coating spalling". An exemplary painting process includes the KTL process.

The reduction in the strength of the materials associated with hydrogen, in particular of steel strips having a strength in the range of the yield limit Re ≧ 500MPa to ≦ 2000MPa, is another significant technical disadvantage in the prior art, since the materials are generally unsuitable for use in the field of safety-relevant components when such a strength of the material is no longer available. The formation and diffusion of hydrogen during the coating process can be effectively reduced by means of the method according to the invention. It is thus possible to produce steel strips coated with zinc and/or zinc alloy coatings by means of the method according to the invention with direct strength retention. This makes it possible to dispense with a heat treatment step after the coating process, which is required if necessary.

Furthermore, the method according to the invention makes it possible to realize a multilayer structure of the coating by combining different pulse shapes, preferably in electrolytic cells which are passed through one after the other. Thus, one or more different morphologies of deposit metal and/or deposit semimetal can be deposited on the same strip substrate with correspondingly different characteristics. Thus, for example, a layer closer to the substrate with higher adhesion may be deposited first, and then a layer further from the substrate with higher hardness.

Further advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are presented and explained in more detail in the description, wherein further preferred embodiments of the invention are presented. It is pointed out here that all specific device features set forth in the individual method steps can be combined in the same way with the apparatus and/or the method according to the invention without explicit reference thereto and vice versa.

The term metal and/or semimetal is understood to mean the metals or semimetals known In electroplating, In particular chromium (Cr), manganese (Mn), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), gold (Au), silver (Ag), zinc (Zn), cadmium (Cd), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi) and/or mixtures or alloys thereof, where the metals and/or semimetals can be selected from groups 6 to 15, alone or In combination.

The coating section of the apparatus may essentially comprise an electrolytic cell with an anode, which is constructed, for example, in the form of a plate anode. In a further development, only one cell can comprise two anodes, which are arranged one after the other, for example in the direction of travel of the strip, so that the strip-shaped substrate can be coated on one side. In a preferred embodiment variant, the two anodes can be constructed in an anode assembly in which the two anodes are then arranged parallel to one another in an electrolytic cell.

In a preferred embodiment variant, the coating section comprises at least two electrolytic cells, more preferably at least three electrolytic cells, still more preferably at least four electrolytic cells, further preferably at least five electrolytic cells, and for reasons of process economy is limited to at most 20 electrolytic cells, preferably to at most 16 electrolytic cells, more preferably to at most 15 electrolytic cells. A plurality of electrolytic cells are preferably arranged one after the other in the direction of travel of the strip, through which the electrically conductive strip and/or the band-shaped fabric is then guided in the coating section.

Each cell may be in the form of a horizontally constructed cell or, preferably, in the form of a vertically constructed cell through which the respective substrate to be coated is guided by reversing rollers.

The coating process in the individual cells takes place in an electrolyte through which the electrically conductive strip and/or the band is guided. The electrolyte medium is typically aqueous and typically has a pH of less than 5.0. Alternatively, the electrolyte medium may also be formed by a non-aqueous medium, such as an ionic liquid. Preferred ionic liquids include a mixture of choline chloride and urea.

The modulated current is provided by a pulse rectifier, which is implemented in switching power supply technology. The pulse rectifier constructed in this way is defined in that the alternating voltage at the power supply terminals is first rectified and smoothed. The dc voltage generated at this time has a significantly higher frequency, typically in the range of 5kHz to 300kHz, is then divided, converted at a high frequency and then rectified and filtered. Superimposed voltage and current regulation usually works by pulse width modulation or pulse phase modulation.

With the high frequencies of the power transmitter, the converter is constructed significantly smaller, so that the energy losses are significantly lower. Due to the system, a significantly higher performance efficiency of the direct current supply and thus of the entire production plant is thereby obtained.

Depending on the type of construction, the pulse rectifier can be provided in a modular construction. This results in a significantly higher availability, since the performance to be provided by the defective module can be assumed by another module and can be replaced quickly when the defective module is repaired.

A further advantage is that the quality of the direct current, in particular its low residual ripple, is significantly better with lower losses, the maintenance of defective components can be carried out significantly faster and more simply than in conventional thyristor-based direct current electrolysis, and the existing direct current/direct voltage supply system can be expanded by further modules afterwards by using corresponding regulation techniques, by means of which the performance of the direct current/direct voltage supply system can be increased.

The at least one pulse rectifier providing the modulated current is advantageously electrically connected by its negative pole to the at least one electrically conductive roller and by its positive pole to the at least one anode. In this connection, it is preferably provided that at least one pulse rectifier, particularly preferably each of the pulse rectifiers, is electrically connected in the coating section to a central control unit, by means of which the entire coating process is regulated. At least one pulse shape of the pulse shape sequence is transmitted by the control unit to at least one pulse rectifier, preferably to each pulse rectifier, which transmits the pulse shape signally to the respective associated electrolytic cell.

The pulse shape of the pulse shape sequence typically comprises at least one cathodic pulse, at least one anodic pulse, and/or at least one pulse pause (pulseusszeit), wherein the cathodic and anodic pulses are defined by pulse durations and their respective shapes, e.g. rectangles.

The at least one anode is preferably configured as a plate anode. Such plate anodes can in principle be designed in the form of soluble or insoluble anodes. For soluble anodes, also referred to as active anode systems, the anode goes into solution during electrolysis. On the other hand, insoluble anodes, which are also referred to as inert anode systems, do not go into solution during electrolysis. The insoluble anode comprises, on the one hand, a support material and a coating applied to the support material, which coating may also be referred to as active layer, and, on the other hand. Titanium, niobium or other inert metals are generally used as support materials here, but materials which are inert under the electrolysis conditions are used in any case. Materials commonly used as the active layer are electron-conducting materials such as platinum, iridium or other noble metals, their mixed oxides or compounds of these elements. The active layer can be applied directly to the surface of the carrier material or on a substrate arranged at a distance from the carrier material. Also usable as substrate in particular are materials which are support materials, i.e. for example titanium, niobium, etc.

At least one anode can preferably be formed in one piece and/or according to an advantageous embodiment variant from at least two or more sub-anodes configured in the form of rods, wherein then each of the sub-anodes is electrically connected to a power supply. At least two or more bar-shaped sub-anodes are advantageously arranged in such a way that the distance of each sub-anode from the strip can be adjusted over the width of the strip. The locally different layer thicknesses can thereby be applied and/or corrected by desorption along the strip width of the substrate, i.e. the electrically conductive strip and/or the band fabric, by adjusting the distance of each of the sub-anodes from the strip and/or by adjusting the current density via a pulse rectifier. Thus, the sub-anodes arranged at the strip edges may for example be provided with a lower current density than the sub-anodes of the strip arranged in the middle section and/or may be positioned at a larger distance relative to the strip in order to control the deposition of metal and/or semi-metal at the strip edges.

In a particularly advantageous embodiment variant, the at least one electrolytic cell comprises at least one anode arrangement comprising two anodes arranged parallel to one another, through which an electrically conductive strip and/or a web is guided. In a configuration of this configuration, provision is preferably made for each of the anodes of the at least one anode arrangement to be energized by means of a separate pulse rectifier, so that each of the anodes is in each case electrically connected to the positive pole of each pulse rectifier and the negative pole of each pulse rectifier is electrically connected to the at least one electrically conductive roller. In other words, the cell comprises in this configuration two anodes, two pulse rectifiers and a conductive roll through which the strip substrate is connected to the cathode.

In a further preferred embodiment variant, the at least one electrolytic cell comprises at least two anode arrangements, each having two anodes arranged parallel to one another, through which an electrically conductive strip and/or a web is guided. If the electrolytic cell is designed as an immersion bath, it is particularly preferred if the electrically conductive strip and/or band is reversed between at least two anode arrangements by reversing rollers, which are optionally arranged in the electrolytic cell. In the arrangement thus constructed, each of the anodes of the at least two anode assemblies is likewise energized by a separate pulse rectifier, so that in this arrangement four pulse rectifiers are provided in total. In this case, each of the four anodes is electrically connected to the positive pole of each pulse rectifier, and the negative poles of the two pulse rectifiers are electrically connected to one of the two electrically conductive rollers. In other words, the electrolytic cell comprises in this configuration four anodes, four pulse rectifiers, two conductive rollers and if necessary a reversing roller arranged inside the electrolytic cell.

In a further preferred embodiment variant, the electrolytic cell can be formed essentially from the anode assembly in such a way that both open sides of the anode assembly are closed. The strip substrate is guided through a partially closed space defined by the anode arrangement and is flushed with electrolyte in this space. The electrolyte can be supplied to the space over the entire cross section and can flow through the space, for example, by means of a corresponding pump. This configuration has a smaller structural space with respect to the immersion tank and therefore requires a smaller volume of electrolyte.

In a particularly preferred embodiment variant, the coating section comprises a plurality of electrolytic cells arranged one after the other in the running direction of the strip, through which the electrically conductive strip and/or the band-shaped fabric is guided. In this connection, it is advantageously provided that the electrically conductive strip and/or the band fabric is reversed between at least two electrolytic cells, more preferably between each of the plurality of electrolytic cells, by at least one reversing roll designed as an intermediate electrically conductive roll and, if appropriate, additionally connected to the cathode. In the exemplary embodiment variant with two electrolysis cells, which each comprise two anode assemblies, each of the anodes of the four anode assemblies is likewise energized by a separate pulse rectifier, so that in this configuration there are provided in total eight pulse rectifiers. In this case, each anode of the total of eight anodes is electrically connected to the positive pole of each pulse rectifier. With regard to the cathode connection, provision is made for it to be assigned to a total of three electrically conductive rollers, so that the negative poles of the respective two pulse rectifiers are in each case electrically connected to one of the two outer electrically conductive rollers (strip inlet electrically conductive roller and strip outlet electrically conductive roller) and the negative poles of the remaining four pulse rectifiers are electrically connected to a reversing roller which is designed as a central electrically conductive roller.

Drawings

The invention and the technical environment are further elucidated below by means of figures and examples. It is noted that the present invention should not be limited by the illustrated embodiments. In particular, unless explicitly stated otherwise, some aspects of the facts set forth in the drawings may also be extracted and combined with other constituents and findings from the present description and/or drawings. It is to be noted in particular that the figures and in particular the scale shown are purely schematic. The same reference numerals denote the same objects, so that explanations of other figures can be considered additionally if necessary. Wherein:

figure 1 shows in a schematic representation a first embodiment variant of a part of a coating section of an apparatus for electrolytically coating electrically conductive strips and/or webs with a coating,

figure 2 shows in a schematic representation a second embodiment variant of a part of a coating section of an apparatus for electrolytically coating an electrically conductive strip and/or band fabric with a coating,

figure 3 shows an embodiment variant of a portion of a coating section with n baths,

figure 4 shows an embodiment variant of the sub-anode assembly,

figure 5 shows in a schematic representation a third embodiment variant of a part of a coating section of an apparatus for electrolytically coating an electrically conductive strip and/or band fabric with a coating,

fig. 6 shows a first embodiment variant of a pulse shape, which may form part of a pulse shape sequence,

fig. 7 shows a second embodiment variant of a pulse shape, which may form part of a pulse shape sequence,

fig. 8 shows a third embodiment variant of a pulse shape, which may form part of a pulse shape sequence,

fig. 9 shows a fourth embodiment variant of a pulse shape, which may form part of a pulse shape sequence,

fig. 10 shows a fifth embodiment variant of a pulse shape, which may form part of a pulse shape sequence, and

fig. 11 shows a sixth embodiment variant of a pulse shape, which may form part of a pulse shape sequence.

Detailed Description

Fig. 1 shows a schematic representation of a part of a coating line 1 of an apparatus for electrolytically coating electrically conductive webs and/or webs with a coating. Such an apparatus can comprise, depending on the strip substrate, one or more coiling devices for uncoiling and coiling up the strip to be coated, an inlet store, a withdrawal and straightening machine, a cleaning and activation unit, a coating section 1, a post-treatment unit, an outlet store, an inspection section and a greasing device arranged before the coiling station (coiling device).

According to the coating section 1 shown here, a coating based on a metal and/or semimetal selected from groups 6 to 15 and/or mixtures or alloys thereof can be electrolytically coated on an electrically conductive strip and/or band fabric 2 (e.g. metal strip, steel strip, aluminium strip), plastic strip, plastic film, glass fibre fabric, carbon fibre woven fabric and/or composites thereof. To this end, the coating section 1 in the embodiment variant shown in fig. 1 comprises an electrolytic bath 3, which is configured here as an immersion bath and has a corresponding electrochemically adjusted electrolyte 4, which contains (semi) metal components in the form of cations. Thus, for example, ZnSO can be used at a concentration of 100 to 400g/L₄The aqueous sulfuric acid electrolyte of (a) is used for coating a steel strip with zinc.

In the embodiment variant shown here, the electrolytic cell 3 comprises two anodes 5 which are positioned in the electrolytic cell 3 in such a way that the strip 2 to be coated which can be guided through the electrolytic cell 3 can be guided at a defined and parallel distance with respect to the anodes. Both anodes 5 are designed as one-piece plate anodes and are arranged one behind the other in the strip running direction R, so that the strip 2 can be coated on one side.

Two electrically

conductive rollers

6, 7 are assigned to the electrolytic cell 3, wherein the first electrically conductive roller 6 is arranged in the coating section 1 on the inlet side of the electrolytic cell 3 (strip inlet electrically conductive roller) and the second electrically conductive roller 7 is arranged on the outlet side of the electrolytic cell 3 (strip outlet electrically conductive roller). The strip 2, which has optionally been subjected to a preliminary cleaning and/or activation step, is diverted from a horizontal movement to a vertical movement by means of a strip inlet conductive roller 6, so that the strip enters the electrolytic cell 3 and is connected to the cathode at the same time. The strip 2 is then reversed after the coating process from the vertical movement to the horizontal movement by the strip outlet conductor roller 7, wherein the strip can optionally be additionally connected to the cathode by the strip outlet conductor roller 7. Also arranged in the electrolytic cell 3 is a reversing roll 8, by means of which the strip 2 is reversed.

In order to carry out the coating process, the two anodes 5 are energized by means of a modulated current, which is respectively supplied by a separate pulse rectifier 9, which is implemented in switching power supply technology. Each of the pulse rectifiers 9 is in each case electrically connected by its negative pole to one of the two electrically

conductive rollers

6, 7 and by its positive pole to one of the two anodes 5. The two anodes 5 can be energized by a modulated current in such a way that the coating process can be carried out using a defined pulse shape sequence 10 formed from the individual pulse shapes 11.

Advantageously, the two pulse rectifiers 9 are electrically connected to a central control unit 12, by means of which the respective desired pulse shape 13 of the pulse shape sequence 12 can be transmitted to each of the pulse rectifiers 10, 11. The entire coating process can thus be adjusted in an automated manner.

Fig. 2 shows a second embodiment variant of a part of the coating section 1. Unlike the embodiment variant shown in fig. 1, the electrolytic cell 3 comprises two anode assemblies 13, each of which has two anodes 5 arranged parallel to one another, through which the strip 2 is guided. As can be seen from fig. 2, each of the anodes 5 of the two anode assemblies 13 is likewise energized by a separate pulse rectifier 9. In this case, each of the four anodes 5 is electrically connected to the positive pole of each pulse rectifier 9, and the negative poles of the two pulse rectifiers 9 are electrically connected to one of the two electrically

conductive rollers

6 and 7.

In fig. 3, an embodiment variant of a part of a coating section 1 with n electrolytic cells 3 is shown, of which four are shown by way of example. All the cells 3 are arranged one after the other in the direction of travel R of the strip. Between each of the plurality of electrolytic cells 3, a deflection roller is arranged in the form of an intermediate electrically conductive roller 14, by means of which the strip 2 is deflected from the preceding cell into the next electrolytic cell 3 and is additionally connected to the cathode. As can be gathered from fig. 3, each of the anodes 5 of the plurality of anode assemblies 13 is energized by a separate pulse rectifier 9. In this case, each of the anodes 5 is connected electrically to the positive pole of each pulse rectifier 9. As regards the cathode connections, it is provided that they are distributed over the different

conductive rollers

6, 7, 14 in such a way that the negative poles of the respective two pulse rectifiers 9 are electrically connected to one of the two outer conductive rollers 6, 7 (strip inlet conductive roller and strip outlet conductive roller) and the negative poles of the remaining pulse rectifiers 9 are electrically connected to a deflection roller designed as a central conductive roller 14.

In fig. 4, an embodiment variant of the sub-anode assembly 15 is shown, which comprises a plurality of sub-anodes 16 of rod-like configuration, wherein each of the sub-anodes 16 is electrically connected to the negative pole of the power supply or pulse rectifier 9.

In fig. 5, a third embodiment variant of a part of the coating section 1 is shown. The electrolytic cell 3 is formed here primarily from the anode assembly 13 in such a way that its two open sides are closed. The strip 2 is guided through a partially closed space delimited by the anode assembly 13 and is flushed in this space with the electrolyte 4. The electrolyte 4 is fed from a container 17 arranged below the anode assembly 13 by means of a pump 18 into the space, where the electrolyte flows through the entire cross-section of the space.

Fig. 6 to 11 show different embodiment variants of a pulse profile 11 which forms part of a pulse profile sequence 10 according to which a coating process is carried out in a coating line 1.

In fig. 6, an initial current pulse of a time length t is shown, which is then reduced to a constant current intensity. The initial current pulse can be used to increase the number of nuclei on the cathode, so that fine crystalline forms are deposited. In contrast, the dashed lines in fig. 6 to 11 show a cathodic current that is constant over time, as used in direct current electrolysis (DC electrolysis).

In fig. 7, a pulse waveform 11 is shown, which first has a high initial current pulse (vortromipuls), followed by a first, higher constant current value and a second, lower constant current value. After time t, the current reverses polarity such that the cathode operates as an anode. The crystal tips or the less noble dendritic (semi-) metal and/or layer elevations at the location of the high current density (edge effect) can thus be reversibly and specifically cut off, so that, in turn, a higher deposition rate at the location of the high current density can be suppressed or slowed down under the action of the subsequent cathode.

An embodiment variant is shown in fig. 8, which shows a repeating pulse shape 11 of the same design in terms of current value and time. The relaxation of the nernst double layer, which is associated with the reduction of diffusion layers that impede the transport of material, is achieved by switching off the pause current and thus supports the formation of a uniform coating thickness on the surface of the strip.

In fig. 9, a pulse waveform 11 is shown with two successive higher current pulses, which are periodically used in the pulse waveform 11 in order to minimize and/or suppress dendritic crystal growth.

In fig. 10 a pulse waveform 11 is shown, which shows a high current pulse, a phase of cathodic deposition, and a reversal of the current, and thus the switching of the cathode and anode. The reduction of the crystal tips and in particular of the deposited (semi-) metal due to edge effects and the suppression of such effects when switching back to the cathode is thereby achieved by two temporally and numerically different pulses, which are matched to the crystal transformation, more precisely the kinetics of the (semi-) metal solution (slow or spontaneous crystal transformation).

Fig. 11 shows a pulse waveform 11 with periodic rectangularly formed current pulses, which pulse waveform 11 can be used in combination with one of the previously described pulse waveforms for forming a multilayer cathode coating. In this case, in the cathodic phase, the coating is deposited galvanically on the strip, then the current, which is lower in value, is applied by the reverse pulse anode, and the deposition is interrupted. The switching time through the anode is preferably cut to the top of the crystal and the other (semi-) metal layer is deposited on the already existing layer again by cathodic switching. By means of the pulse shape shown in fig. 11, a (semi-) metallic coating can be formed periodically and in layers, which is associated with an improved corrosion resistance. The so-called reverse pulse current method is also called bipolar pulse current method, since the conduction of the cathode and anode currents is exchanged here, i.e. the current changes when passing through the zero point. In other words, the cathode is temporarily switched to the anode, so that the deposition process of electroplating can be temporarily reversed. The current value, duration and polarity exchange can be designed according to the user's subscription and optimized for the process.

List of reference numerals

1 coating section

2 strip/fabric/cathode

3 electrolytic cell

4 electrolyte solution

5 Anode

6 first conductive roll/strip entry conductive roll

7 second conductive roll/strip outlet conductive roll

8 reversing roller

9 pulse rectifier

10 pulse waveform sequence

11 pulse waveform

12 control unit

13 anode assembly

14 intermediate conductive roller

15 sub-anode assembly

16 sub-anodes

17 Container

18 pump

R direction of travel of the strip

Claims

1. Method for the electrolytic coating of electrically conductive strips and/or webs (2), in particular metal strips, plastic strips, glass fiber fabrics, carbon fiber woven fabrics and/or composites thereof, with a coating based on metals and/or semimetals selected from groups 6 to 15 and/or mixtures thereof, wherein the electrically conductive strips and/or webs (2) are fed after necessary prior cleaning and/or activation to a coating section (1) and are continuously electrolytically coated in the coating section, which comprises at least one, preferably at least two or more electrolytic cells (3), wherein the electrically conductive strips and/or webs (2) are first connected to a cathode by means of at least one electrically conductive roller (6) and are parallel within the at least one electrolytic cell (3) at defined intervals to at least one anode(s) arranged in the electrolytic cell(s) (3) 5) Guiding is carried out, wherein the at least one anode (5) is energized by means of a modulated current and a coating process is carried out within the coating section (1) using a defined pulse waveform sequence (10) formed by at least one pulse waveform (11), wherein at least one metal selected from the group of metals from the groups 6 to 15 and/or at least one semimetal selected from the semimetals and/or mixtures thereof is deposited from an electrolyte (4) onto the electrically conductive strip and/or the band fabric (2) according to the pulse waveform sequence (10) and the coating is formed.

2. The method according to claim 1, wherein the modulated current is provided by at least one pulse rectifier (9) having a negative pole electrically connected to the at least one conductive roller (7) and a positive pole electrically connected to the at least one anode (5).

3. Method according to claim 2, wherein the at least one pulse rectifier (9) is electrically connected with a central control unit (12) by means of which the coating process is controlled and/or regulated.

4. Method according to claim 3, wherein at least one pulse shape (11) of the pulse shape sequence (10) is transmitted by the central control unit (12) to at least one pulse rectifier (9), preferably to each of the pulse rectifiers (9).

5. The method according to any one of the preceding claims, wherein at least one pulse shape (11) of the pulse shape sequence (10) comprises at least one cathodic pulse, at least one anodic pulse, and/or at least one pulse pause, and wherein the cathodic pulse and the anodic pulse are defined by a pulse duration.

6. The method according to any one of the preceding claims, wherein the at least one anode (5) is configured as a plate anode, preferably formed in one piece and/or formed by at least two or more sub-anodes (16) configured as rods.

7. The method according to any one of the preceding claims, wherein the electrically conductive strip and/or webbing (2) is guided inside the at least one electrolytic cell (3) through at least one anode assembly (13) comprising two anodes (5) arranged parallel to each other, preferably through at least two anode assemblies (13) each having two anodes (5) arranged parallel to each other.

8. A method according to claim 7, wherein each of the anodes (5) of the anode assembly (13) is energized by a separate pulse rectifier (9) such that each of the anodes (5) is electrically connected to the positive pole of each pulse rectifier (9) respectively and the negative pole of each pulse rectifier (9) is electrically connected to the at least one electrically conductive roller (6, 7).

9. The method according to claim 7 or 8, wherein the electrically conductive strip and/or fabric (2) is reversed between at least two anode assemblies (13) by a reversing roll (8) optionally arranged within the electrolytic cell (3, 5).

10. The method according to any one of the preceding claims, wherein the electrically conductive strip and/or band fabric (2) is guided within the coating section (1) through a plurality of at least two electrolytic cells (3) arranged one after the other in the strip travel direction (R).

11. The method according to claim 10, wherein the electrically conductive strip and/or the band (2) is reversed between at least two electrolysis cells (3) by means of at least one reversing roll configured as an intermediate electrically conductive roll (14) and, if necessary, additionally connected to a cathode.

12. An apparatus for electrolytically coating electrically conductive tapes and/or band fabrics (2), preferably metal tapes, plastic tapes, glass fibre fabrics, carbon fibre woven fabrics and/or composites thereof, with a coating based on a metal and/or semimetal selected from groups 6 to 15 and/or mixtures thereof, the apparatus comprising:

optionally a cleaning and/or activation unit, in which the electrically conductive strip and/or the band (2) can be cleaned and/or activated;

a coating section (1) having at least one, preferably at least two or more electrolytic cells (3) in which the electrically conductive strip and/or band fabric (2) can be continuously electrolytically coated, and

at least one electrically conductive roller (6) by means of which the electrically conductive strip and/or band fabric (2) can be connected to a cathode, wherein the at least one electrolytic cell (3) comprises at least one anode (5) which is arranged such that the electrically conductive strip and/or band fabric (2) which can be guided through the at least one electrolytic cell (3) can be guided at a defined and parallel distance with respect to the at least one anode (5), wherein the apparatus comprises at least one pulse rectifier (9) whose negative pole is electrically connected to the at least one electrically conductive roller (6) and whose positive pole is electrically connected to the at least one anode (5) such that the at least one anode (5) can be energized by means of a modulated current such that the coating process can be carried out within the coating section (1) using a defined pulse waveform sequence (10), wherein the pulse waveform sequence (10) is formed by pulse waveforms (11), wherein at least one metal selected from the metals of groups 6 to 15 and/or at least one semimetal selected from the semimetals and/or mixtures thereof can be deposited on the electrically conductive strip and/or fabric (2) from an electrolyte (4) according to the pulse waveform sequence (10).