CN114174559A

CN114174559A - Method and device for electrolytic coating of electrically conductive strips and/or fabrics using impulse technology

Info

Publication number: CN114174559A
Application number: CN202080055430.7A
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: 2022-03-11
Also published as: WO2021023789A1; EP4010516A1; CN114207190A; WO2021023783A1; WO2021023778A1; EP4010518A1; CN114207191A; CN114174560A; EP4010515A1; US20220275530A1; WO2021023779A1; EP4010517A1

Abstract

The invention relates to an electroplating method and device for the production of electrically conductive strips and/or electrically conductive band-shaped structures, preferably metal strips, such as steel strips; a plastic tape; a fiberglass fabric tape; electrolytically coating a carbon fibre woven fabric tape and/or their composite with a coating based on a metal and/or semimetal selected from groups 6 to 15 and/or mixtures thereof.

Description

Method and device for electrolytic coating of electrically conductive strips and/or fabrics using impulse technology

Technical Field

The invention relates to an electroplating process and apparatus for electrolytically coating electrically conductive strips and/or electrically conductive tape fabrics, preferably metal strips, such as steel strips and/or sheets, plastic strips, glass fiber fabric strips, carbon 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 semi-finished 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. Such strip is 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. These are, for example, protection against corrosion or oxidation, protection against abrasion, production of decorative product properties and/or production of magnetic and/or electrical surface properties.

For example, electrolytically galvanized steel strip obtains effective corrosion protection by the zinc coating and provides a good adhesion base for painting and/or lamination with plastic foils. The chromium coating also provides enhanced corrosion and wear protection and decorative properties to the steel or plastic strip. 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, in particular in terms of economy and economy, is highly dependent on various parameters, such as the type and composition of the electrolyte, its metal salt concentration and temperature, the geometry of the cell and its electrodes, the guidance of the electrochemical current and its value, time and polarity.

In the prior art, electrolytic coating of metal strips is carried out by direct current, wherein thyristor technology is used. Such so-called direct current electrolysis can be designed to be unipolar and to be partially polarity-switched, but does not allow specific current sequences in terms of value, time and polarity. The deposition of metallic and/or semimetallic components at the strip edges of the respective strip substrate has proven to be particularly problematic. These elevated portions can cause edge cracking and pressure deformation of the finished roll of tape. Another problem is the dendritic growth of the very high parts of the strip edges, which fall off from the strip during the coating process as coarse particles, contaminate the electrolyte in the form of particles and then settle or accumulate on the strip surface, which is undesirable in terms of surface quality. In the prior art, so-called edge masks are preferably used. However, these edge masks have to be adapted to the respective bandwidth in a sensory manner by means of electrical adjustment, so that there is a high risk of disturbances and collisions associated with long downtimes. Furthermore, the use of these edge masks requires a significant amount of personnel time to maintain and repair.

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, after necessary prior cleaning and/or activation, the electrically conductive strip and/or the electrically conductive fabric strip, 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 comprising at least one, preferably at least two or more electrolysis cells and is continuously electrolytically coated in the coating station, wherein the electrically conductive strip and/or the fabric strip is first connected to a cathode by means of at least one electrically conductive roller and is guided in the at least one electrolysis cell at a defined distance parallel to the at least one anode arranged in the electrolysis cell.

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

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 defined pulse pattern sequences, wherein a pulse pattern sequence is formed by the individual pulse patterns, wherein, according to the pulse pattern sequence, at least one of the metals from groups 6 to 15 and/or at least one of the semimetals and/or mixtures thereof can be deposited from the electrolyte onto the electrically conductive strip and/or band fabric.

Surprisingly, it has been shown that, with the use of a defined pulse pattern sequence formed from individual pulse patterns, the deposition rate is locally significantly reduced at the location of the high current density, so that the cumbersome installation of the edge mask and its tracking positioning, which are customary in the prior art, can be dispensed with as a result of the change in the strip width and/or the trimming of the strip edge.

Thus, changing the polarity can, for example, reverse the deposition process. By changing the polarity, for example, regions of the (partially) coated substrate can be modified 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 due to the high current density, in particular at the edges of the strip substrate. Thus, changing the polarity, i.e. the anode operation, makes it possible to specifically reduce local overhigh and to equalize the layer thickness of the overhigh with the surrounding regions without reducing the surrounding regions.

The coating process according to the invention is carried out within the coating section using a defined pulse pattern sequence, which is formed by the individual pulse patterns. Here, the pulse pattern sequence may be formed by a unique pulse pattern and/or by a combination of at least two or more different pulse patterns of the pulse pattern set.

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 over its entire surface with a uniform layer thickness in a continuous coating process, which extends uniformly, in particular over the entire strip width, i.e. at the strip edges, and has no local over-coating and/or under-coating.

Furthermore, the use of modulated current in bipolar operation results in a multilayer structure with improved properties. By selecting the pulse pattern, the nucleation, the number thereof 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 pattern, 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 temporally short, but numerically higher, pre-pulse (vorimapple) 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 leads to a finer-grained morphology of the coating.

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 (TI), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi) and/or mixtures or alloys thereof, wherein the metals and/or semimetals can be selected from groups 6 to 15, alone or In combination.

The electrically conductive tape and/or the electrically conductive webbing is preferably selected from the group consisting of metal tape (e.g. steel tape and/or sheet), plastic tape, glass fibre fabric tape, carbon fibre woven fabric tape and/or composites thereof.

Particularly preferably, the electrically conductive strip is a steel strip having a tensile strength of at least R_eNot less than 500MPa, more preferably at least R_e600MPa or more, and most preferably at least R_eNot less than 800 MPa. With respect to the maximum tensile strength, the steel strip is limited to a tensile strength R_e2000MPa or less, more preferably to a tensile strength R_e1500MPa or less, and still more preferably limited to tensile strength R_e≤1200MPa。

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 variant, the two anodes can be formed in an anode arrangement in which the two anodes are arranged parallel to one another in an electrolytic cell.

In a preferred 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 web travel, and the electrically conductive web and/or the band-shaped fabric is then guided through the electrolytic cells in the coating section.

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

The precipitation 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 use of a pulse rectifier makes it possible to define the number, the temporal course and the polarity of the respective desired pulse pattern and thus of the entire pulse pattern sequence, so that the electrolytic process can be optimally matched to the respective system consisting of strip substrate and coating agent according to the predetermined parameters.

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 power to be supplied by the defective module can be absorbed 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 context, 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 pattern of the pulse pattern sequence is transmitted by the control unit to at least one pulse rectifier, preferably to each pulse rectifier, which signals the pulse pattern to the respective associated electrolytic cell.

The pulse patterns of the pulse pattern sequence typically comprise at least one cathodic pulse, at least one anodic pulse, and/or at least one pulse pause time, wherein the cathodic and anodic pulses are defined with respect to the pulse duration and their respective shape, e.g. a rectangle.

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 consists of a carrier material on the one hand and a coating applied to the carrier material on the other hand, which may also be referred to as an active layer. Titanium, niobium or other reactive support metals are generally used as support materials here, but materials which passivate under electrolytic 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 variant by 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 can be energized at a lower current density than the sub-anodes of the strip arranged in the middle section and/or positioned at a larger distance from the strip in order to control the deposition of metal and/or semi-metal at the strip edges.

In a particularly advantageous variant, at least one of the electrolysis cells comprises at least one anode arrangement, which is formed by two anodes arranged parallel to one another, through which an electrically conductive strip and/or a web is guided. In a configuration of this type, it is preferably provided that each of the anodes of the at least one anode arrangement is supplied with current by a separate pulse rectifier, so that each of the anodes is 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 one conductive roll through which the strip substrate is connected to the cathode.

In a further preferred 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 one reversing roller arranged inside the electrolytic cell.

In a further preferred 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 swept by the 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 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 variant with two electrolysis cells, each of the electrolysis cells comprises two anode assemblies, each of the anodes of the four anode assemblies likewise being energized by a separate pulse rectifier, so that in this configuration eight pulse rectifiers are provided in total. In this case, each anode of the total of eight anodes is electrically connected to the positive pole of each pulse rectifier. In the case of the cathode connection provision, it is assigned to a total of three electrically conductive rollers, so that the negative poles of the respective two pulse rectifiers are each 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 field are explained in more detail below with reference to the figures and the examples. It should be noted that the invention should not be limited by the illustrated exemplary embodiments. In particular, unless explicitly stated otherwise, some aspects of the facts explained in the figures may also be extracted and combined with other components and findings from the present description and/or the figures. It is to be expressly noted that the figures, in particular the proportions indicated, are purely diagrammatic. The same reference numerals denote the same objects so that explanations of other drawings may be used as supplementary if necessary. Wherein:

figure 1 shows a schematic view of a first variant of a part of a coating section of a device for electrolytically coating an electrically conductive strip and/or a woven band with a coating,

figure 2 shows a schematic view of a second variant of a part of a coating section of a device for electrolytically coating an electrically conductive strip and/or a woven band with a coating,

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

figure 4 shows a variant of the sub-anode assembly,

figure 5 shows a schematic view of a third variant of a part of a coating section of a device for electrolytically coating an electrically conductive strip and/or a woven band with a coating,

figure 6 shows a first variant of a pulse pattern which may form part of a pulse pattern sequence,

figure 7 shows a second variant of a pulse pattern which may form part of a pulse pattern sequence,

figure 8 shows a third variant of a pulse pattern which may form part of a pulse pattern sequence,

figure 9 shows a fourth variant of a pulse pattern which may form part of a pulse pattern sequence,

FIG. 10 shows a fifth variant of a pulse pattern which may form part of a pulse pattern sequence, an

Fig. 11 shows a sixth variant of a pulse pattern which may form part of a pulse pattern sequence.

Detailed Description

Fig. 1 shows a schematic view of a part of a coating section 1 of an apparatus for electrolytically coating an electrically conductive strip and/or a woven band with a coating. Depending on the strip substrate, such a plant can have one or more coiling devices for uncoiling and coiling up the strip to be coated, an inlet storage device, a withdrawal and straightening machine, a cleaning and activation unit, a coating section 1, a post-treatment unit, an outlet storage device, an inspection section and a preparation device arranged upstream of the coiling station (coiling device).

The coating section 1 according to the invention can be an electrically conductive strip and/or a band fabric 2, for example a metal strip, a steel strip, an aluminum strip, a plastic film, a glass fiber fabric, a carbon fiber woven fabric and/or a composite material thereof, which is electrolytically coated with a coating based on a metal and/or semimetal selected from groups 6 to 15 and/or mixtures or alloys thereof. For this purpose, in the variant shown in fig. 1, the coating section 1 comprises an electrolytic bath 3, which is in this case designed as an immersion bath and has a corresponding electrochemically controlled electrolyte 4 containing (semi-) metallic constituents 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 variant shown here, the electrolytic cell 3 comprises two anodes 5 which are positioned in the electrolytic cell 3 such that the strip 2 to be coated which can pass through the electrolytic cell 3 can be passed 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, so that the coating process can be carried out using a defined pulse pattern sequence 10 formed by the individual pulse patterns 11.

Advantageously, the two pulse rectifiers 9 are electrically connected to a central control unit 12, by means of which the respective desired pulse patterns 13 of the pulse pattern 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 variant of a part of the coating section 1. Unlike the 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 one positive pole of each pulse rectifier 9, and the negative poles of the respective two pulse rectifiers 9 are electrically connected to one conductive roll of the two

conductive rolls

6 and 7.

Fig. 3 shows a variant of a part of a coating line 1 with n electrolytic cells 3, 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 electrically connected to a respective positive pole of each pulse rectifier 9. In regard to the cathode circuit provision, these are distributed over the different

conductive rollers

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

Fig. 4 shows a variant of the sub-anode arrangement 15, 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.

Fig. 5 shows a third variant of a part of the coating section 1. 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 arrangement 13 and is swept in this space by 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 variants of the pulse pattern 11 which form part of a pulse pattern sequence 10 according to which the coating process is carried out in the coating section 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 pattern 11 is shown, which first has a high starting current pulse, followed by a higher first constant current value and a lower second constant current value. After time t, the current reverses polarity such that the cathode operates as an anode. The crystal tips or the lower-quality dendritic (semi-) metal and/or layer elevations at the locations of high current density (edge effect) can thus be reversibly and exclusively reduced, so that, in turn, a higher deposition rate at the locations of high current density can be suppressed or slowed down by the subsequent cathode.

Fig. 8 shows a variant, which shows a repeating pulse pattern 11 of the same design with regard to 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 pattern 11 is shown with two successively higher current pulses, which are used periodically in the pulse pattern 11 in order to minimize and/or suppress dendritic crystal growth.

In fig. 10 a pulse pattern 11 is shown, which shows a high current pulse, a phase of cathode deposition, and a reversal of the current, and thus the switching of the cathode and the 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 are thereby achieved by two temporally and numerically different pulses, which are matched to the dynamics of the crystal transformation, more precisely the (semi-) metal solution (slow or spontaneous crystal transformation).

Fig. 11 shows a pulse pattern 11 with periodic square-shaped formed current pulses that can be used in combination with one of the previously described pulse patterns to form a multilayer cathode coating. In this case, in the cathodic phase, the coating is deposited galvanically on the strip, and then the anode is supplied with a current of a smaller value by means of a reverse pulse, and the deposition is interrupted. The switching time by the anode preferably cuts the crystal tip and another (semi-) metal layer is deposited again by cathodic switching on the already existing layer. By means of the pulse pattern 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 pattern sequence

11 pulse pattern

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) comprising at least one, preferably at least two or more, electrolytic cells (3) and are continuously electrolytically coated in this coating section, 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 guided within the at least one electrolytic cell (3) at defined intervals parallel to at least one anode (5) arranged in the electrolytic cell (3) -wherein the at least one anode (5) is energized by means of a modulated current and the coating process is carried out within the coating section (1) using a defined pulse pattern sequence (10) formed by at least one pulse pattern (11), wherein at least one metal selected from the group of metals from groups 6 to 15 and/or at least one semimetal selected from the group of semimetals and/or mixtures thereof is deposited from an electrolyte (4) on the electrically conductive strip and/or band fabric (2) according to the pulse pattern sequence (10) and the coating is formed.

2. Method according to claim 1, characterized in that said modulated current is provided by at least one pulse rectifier (9) having its negative pole electrically connected to said at least one conductive roller (7) and its positive pole electrically connected to said at least one anode (5).

3. Method according to claim 2, characterized in that 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, characterized in that at least one pulse pattern (11) of the pulse pattern 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 of the preceding claims, wherein at least one pulse pattern (11) of the pulse pattern 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. Method according to any of the preceding claims, characterized in that the at least one anode (5) is configured as a plate anode, which is preferably formed in one piece and/or is formed by at least two or more sub-anodes (16) configured as rods.

7. The method according to any of the preceding claims, characterized in that 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) consisting of 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, characterized in that 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 roll (6, 7).

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

10. The method according to any of the preceding claims, characterized in that 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, characterized in that 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 designed 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 web (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 web (2) which can be guided through the at least one electrolytic cell (3) can be guided at a defined and parallel spacing relative 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 pattern sequence (10), wherein the pulse pattern sequence (10) is formed by pulse patterns (11), 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 is deposited from an electrolyte (4) on the electrically conductive strip and/or fabric (2) according to the pulse pattern sequence (10).