EP0704558B1 - Cell for continuous electrodeposition of metal alloys - Google Patents

Cell for continuous electrodeposition of metal alloys Download PDF

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Publication number
EP0704558B1
EP0704558B1 EP95401908A EP95401908A EP0704558B1 EP 0704558 B1 EP0704558 B1 EP 0704558B1 EP 95401908 A EP95401908 A EP 95401908A EP 95401908 A EP95401908 A EP 95401908A EP 0704558 B1 EP0704558 B1 EP 0704558B1
Authority
EP
European Patent Office
Prior art keywords
strip
anode
edge
alloy
electroplating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP95401908A
Other languages
German (de)
French (fr)
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EP0704558A1 (en
Inventor
Franco Delfrate
Claude Arnoux
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sollac SA
Original Assignee
Sollac SA
Lorraine de Laminage Continu SA SOLLAC
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Publication of EP0704558A1 publication Critical patent/EP0704558A1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/06—Wires; Strips; Foils
    • C25D7/0614—Strips or foils
    • C25D7/0671—Selective plating
    • C25D7/0678—Selective plating using masks
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/06—Wires; Strips; Foils
    • C25D7/0614—Strips or foils
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/22—Electroplating: Baths therefor from solutions of zinc
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/06—Wires; Strips; Foils
    • C25D7/0614—Strips or foils
    • C25D7/0642—Anodes

Definitions

  • the invention relates to an electroplating cell for the continuous coating of metal strips with a layer of metal alloy.
  • the strip is generally passed through an installation which comprises a succession of electroplating cells, each cell contributing to the formation of a portion of the layer, or "sublayer"; the stack of sub-layers forms the alloy layer.
  • such a sheet coated by electrodeposition with a layer of metal alloy and then painted, in particular by cataphoresis does not exhibit sufficient resistance to the gravel test, in particular for automotive applications;
  • the gravel test consists of projecting solid gravel onto the painted sheet and evaluating the resistance to gravel, for example by counting the number of impacts on the sheet where the paint has been torn off; after the graveling test of such a painted sheet metal, numerous flaking of paint is observed and it is found that the tearing off of the paint flakes actually occurs in the thickness of the coating or of the electrodeposited layer.
  • the object of the invention is to improve the quality, in particular the strength mechanical, coatings of metal alloys deposited continuously by electrodeposition on metal strips.
  • the invention therefore also aims to limit the aforementioned drawbacks concerning the shaping and painting of the metal strips or sheets coated with alloy.
  • the subject of the invention is an electroplating cell for the continuous coating of a metal strip, in particular with a layer of metallic alloy, comprising an electrolysis tank containing an electroplating bath, at least one anode immersed in said bath and having an active surface delimited by edges, means for passing the strip in the bath opposite said active surface from one edge of said surface to another opposite edge of the same surface, said means defining a path of strip running, and means for passing an electric current between said anode and said running strip serving as a cathode, characterized in that said active surface of each submerged anode is bordered on each of said two opposite edges by a mask having, along said corresponding edge and facing said travel path, an electrically insulating surface, closer to said travel path that said rim, said mask projecting towards the outside of said active anode surface with a width called overflow, measured along the direction of travel, at least equal to the distance which separates said edge from said travel path, and said mask covering the edge of said active anode surface over a width known as covering
  • the invention also relates to an electroplating installation for the continuous coating of a metal strip, in particular with a layer of metallic alloy, comprising a cascade succession of cells according to the invention.
  • the invention also relates to the use of electroplating cells according to the invention for the continuous coating of metal strips with a layer of metal alloy.
  • the subject of the invention is also a method of coating a metal strip by electrodeposition of a metal alloy, in particular based on zinc, using an installation comprising several cells according to the invention arranged in cascade in which said strip is passed successively through said cells of the installation, an electric current is circulated between the anodes of the cells and said moving strip, characterized in that the running speed of said strip in the installation is greater than 50 m / minute and / or the density of the electric current flowing between the anodes of the cells and said strip is greater than 50 A / dm2.
  • the plating installation comprises several identical plating cells arranged in cascade.
  • the first cell of the installation is represented in FIG. 1, designated as a whole by the reference 1, and comprises an electrolysis tank 2 containing an electroplating bath S, means ensuring the movement of a metal strip B in the bath S and defining a strip running path, and, positioned successively under the strip running path and facing it, two anodes 3; cell 1 also comprises means for circulating an electric current between said anodes 3 and strip B running as cathode, which are not shown here.
  • the electroplating cell can comprise a single anode or more than two successive anodes.
  • the running means comprise tape support cylinders with parallel axes, namely two tape entry cylinders 5, 6, two tape exit cylinders 7, 8 and an intermediate cylinder 9 for tape support in the tank.
  • tape support cylinders with parallel axes namely two tape entry cylinders 5, 6, two tape exit cylinders 7, 8 and an intermediate cylinder 9 for tape support in the tank.
  • the three cylinders 6, 9, 7 immersed in the electrolytic cell define the strip running path in the electrolytic cell, which here is approximately in a horizontal plane.
  • the two anodes 3 are each positioned between two submerged cylinders and each have a planar active surface 13 placed below the strip running path and oriented parallel to it and towards it.
  • the distance between the active surface 13 of the anodes 3 of the strip running path is generally between 0.5 and 10 cm in an industrial cell.
  • the active surfaces 13 of the anodes 3 extend transversely to the direction of travel over the entire width of the strip to be coated. Furthermore, the active surfaces 13 of the anodes 3 extend along the direction of travel of the strip between two opposite edges 3A, 3B.
  • the distance between the active surface 13 of the anodes 3 of the strip running path is commonly about 3 cm.
  • each anode 3 is bordered, along these two opposite edges 3A, 3B, by two masks 4A, 4B in the form of narrow flat panels.
  • Each panel-shaped mask 4A, 4B extends along a corresponding rim 3A, 3B of the active anode surface 3 and is arranged in a plane approximately parallel to the strip running path.
  • the masks are made of electrically insulating material, preferably of composite material or plastic.
  • the masks 4A, 4B which each run along an edge 3A, 3B of the active anode surface, are always closer to the strip running path than the anodes.
  • the distance which separates a mask 4A, 4B from the strip travel path is less than 0.5 times the inter-electrode distance, ie that which separates the corresponding flange 3A, 3B from the same travel path.
  • the masks can be in a form different from that of a narrow flat panel while offering, facing the running path and along an edge of the active anode surface, a surface electrically insulating masking and closer to the running path than said flange.
  • the thickness of the masks 4A, 4B is preferably much less than said inter-electrode distance, so that said masks can be partially inserted between the anode and the strip running path under the corresponding surface rim 3A, 3B active anode 13.
  • the thickness of the masks 4A, 4B is however sufficient to provide an electrical masking function between the active surface 13 of the anode and the running strip serving as the cathode.
  • the thickness of the masks is commonly of the order of 1 cm.
  • each mask 4A, 4B which runs along a rim 3A, 3B of active anode surface, has a continuous intersection with the abstract surface passing through said rim 3A, 3B and orthogonal to the strip running path.
  • the mask 4A, 4B in the form of a narrow flat panel, extends in width on each side of said intersection, that is to say, covering on one side the corresponding rim 3A, 3B of the active anode surface and largely protruding from the other side towards the outside of said active surface.
  • the so-called overlap width measured along the direction of travel, is less than the distance between said edge of said travel path.
  • the overlap width of the mask 4A, 4B relative to the rim 3A, 3B corresponding to the anode 3 is commonly less than 1 cm.
  • the overflow width of the mask 4A, 4B relative to the corresponding rim 3A, 3B of anode 3 is greater than or equal to the inter-electrode distance, at the level of said rim.
  • each anode 3 is thus bordered by two masks 4A, 4B along two opposite edges 3A, 3B; according to a variant of the invention, two masks, which immediately follow one another along the strip running path and which frame two successive anodes, can be contiguous and form only one flat panel. The same mask can thus be used to border two successive anodes.
  • the means for circulating an electric current between the anodes 3 and the running strip serving as the cathode comprise the two emerged cylinders 5, 8 which are conductive, are known in themselves and are not described here in detail.
  • FIG. 2 thus represents a cross-sectional diagram of a radial cell, designated as a whole by the reference 1 ′, comprising a tank 2 ′ containing an electroplating bath S ′, strip running means comprising two emerging conductive cylinders 5 ', 8' and a partially submerged cylinder 9 'whose surface defines the strip running path, two submerged anodes 3' in the shape of an arc of a circle facing the submerged part of said cylinder 9 ', and three masks 10, 11 and 12.
  • the first mask 10 is located at the level of the anode rim which sees the strip re-entering the bath and the third mask 12 is located at the level of the last anode rim which sees the strip exiting the bath.
  • the first and the third masks may have an emerged part.
  • the second mask 11 is an intermediate mask which extends between the two anodes 3 'and therefore borders both of the edges of each anode 3'.
  • the masks can be supported by said ramps.
  • said ejector can advantageously serve as a mask provided that it is electrically insulating and the masking surface which faces the path of tape scrolling is not necessarily flat.
  • Each cell of the installation contributes to the formation of a portion of the coating layer, or "sublayer" and the stacking of the sublayers forms the alloy layer.
  • the cells 1 of the installation have soluble zinc anodes.
  • the tanks 2 of the different cells 1 are filled with an electroplating bath S based on chloride anions and containing zinc cations and alloying elements in proportions and concentrations known in themselves to obtain said layer of alloy with the desired composition.
  • said alloying elements are chosen from nickel, iron or cobalt.
  • the tape B is scrolled successively in each of the cells of the installation.
  • an electric current is passed between the anodes of the different cells and the steel strip B serving as the cathode.
  • the tape running speed and the electric current density of the different cells are adjusted in a manner known per se, in particular as a function of the thickness of the desired plating layer.
  • the tape running speed is greater than 50 m / min.
  • the current density is greater than 50 A / dm2.
  • the steel strip B then emerges from the installation coated with a layer of alloy.
  • the Applicant has also surprisingly found that said painted strip, in particular by cataphoresis, withstood the gravel test much better than a sheet conventionally coated with the same layer of alloy and painted in the same way.
  • the cells of the electrodeposition installation are equipped with insoluble electrodes and the cells of the cells are filled with an electrolysis bath based on anions other than chloride ions, in particular of sulfate ions.
  • the electrodeposited layer is a metal alloy based on metals other than zinc, in particular based of tin and lead, or based on iron and nickel, or based on copper and nickel.
  • the composition of the electroplating bath is adapted in a manner known per se to the type of alloy of the coating to be deposited.
  • the above-described electrodeposition installation can be used to coat steel strip or other metal strips, in particular stainless steel strips.
  • the Applicant has found that by using an installation comprising a succession of cells according to the invention for continuously coating a metal strip, in particular of steel, with a layer of alloy, notably based on zinc, one obtains advantageously a coating having in its thickness a great homogeneity, in particular of composition, and excellent mechanical properties, in particular a resistance to delamination.
  • the applicant considers that the masks bordering the anodes of the electroplating cells of the installation cause a sudden variation in the current density at the input and at the output of the various anodes of the installation, which makes it possible to ensure deposition under more homogeneous current density conditions which guarantee a constant alloy composition over the thickness of the layer.
  • the purpose of this test is to prepare a coating of zinc alloy on a steel strip in electroplating cells according to the invention.
  • the electrodeposition installation comprises a succession of radial cells 1 ′ according to the invention, of the type previously described and shown in FIG. 2.
  • the partially submerged cylinder 9 ' which defines the strip running path in the cell has a width of 2 m and a diameter of 2 m.
  • the two 3 'anodes are made of zinc and soluble.
  • the average distance between the anodes and said cylinder 9 ' is 3 cm.
  • the three masks 10, 11 and 12 are arranged about 1 cm from said cylinder 9 'and barely penetrate, to a depth of less than 1 cm, in the interval which separates the anodes 3' from said cylinder 9 '.
  • the three masks 10, 11, 12 which border the two anodes are flat polypropylene panels 2 m long, about 20 cm wide and 1 cm thick.
  • the temperature of the bath is maintained at 57 ° C. and the pH of the bath is maintained at a value of approximately 4.5 by additions of hydrochloric acid.
  • the strip to be coated is made of steel, has a width of 1.5 m and a thickness of 1 mm.
  • the strip is scrolled through the installation at a speed of 100 m / min. and an electric current is passed between the anodes and the strip of 100 A / dm2.
  • a strip coated on one face with a layer of zinc alloy containing 12% by weight of nickel and with a thickness of approximately 4 micrometers is obtained.
  • the coating of the sheet blank A was prepared discontinuously in a manner known per se by immersing and maintaining the said sheet blank to be coated in an electroplating cell facing an anode, without scrolling, and by passing an electric current between said anode and the sheet blank serving as cathode.
  • the sheet blank B is cut from a strip of steel coated continuously according to the prior art, that is to say by scrolling of said strip in electroplating cells which are not provided with anode edge masks .
  • the sheet blank C is cut from a continuously coated steel strip according to test No. 1 above.
  • the sheet blanks A, B, C are stamped and, after the stamping operation, the weight loss of each sheet blank compared to the surface of the surface is measured. coating.
  • the result of the measurement is an indicator proportional to the crumbling or "dusting" of the coating.
  • the alloy coating continuously prepared on a steel sheet in electroplating cells according to the invention has excellent resistance to crumbling and "dusting".
  • each sheet blank A, B, C of test No. 2 is painted by cataphoresis and under the same conditions.
  • the thickness of the paint layer is approximately 100 micrometers.
  • Each sheet blank A, B, C is then subjected to the same gravel test, which consists in projecting gravel for a predetermined time on the sheet blanks to be tested.
  • the impact of gravel on the blanks of painted sheet A, B, C may or may not cause the paint and coating to tear off.

Abstract

Electrolytic cell includes means for passing a metallic strip through an electrolytic bath equIpped with anodes (3) having bevelled edges (3A,3B). The edges of each anode are bordered by an insulation plate (4A,4B) located between the anode and strip. The plates extend beyond the edges of the anode in a direction parallel to the strip by an amount at least equal to the distance between the anode edges and the strip. The length of plate which covers the edge of the anode is less than the distance between the anode and strip.

Description

L'invention concerne une cellule d'électrodéposition pour le revêtement en continu de bandes métalliques par une couche d'alliage métallique.The invention relates to an electroplating cell for the continuous coating of metal strips with a layer of metal alloy.

Pour revêtir une bande métallique d'une couche d'alliage, notamment une tôle d'acier d'une couche d'alliage de zinc, on fait généralement défiler la bande dans une installation qui comporte une succession de cellules d'électrodéposition, chaque cellule contribuant à la formation d'une portion de la couche, ou "sous-couche" ; l'empilement des sous-couches forme la couche d'alliage.To coat a metal strip with an alloy layer, in particular a steel sheet with a zinc alloy layer, the strip is generally passed through an installation which comprises a succession of electroplating cells, each cell contributing to the formation of a portion of the layer, or "sublayer"; the stack of sub-layers forms the alloy layer.

Dans la mise en oeuvre ou l'utilisation d'une tôle revêtue en continu par électrodéposition d'une couche d'alliage métallique, notamment d'une tôle revêtue d'alliage de zinc, on a constaté un certain nombre de problèmes, notamment au moment de la mise en forme ou après mise en peinture.In the implementation or the use of a sheet coated continuously by electrodeposition of a layer of metallic alloy, in particular of a sheet coated with zinc alloy, a number of problems have been found, in particular in time of shaping or after painting.

A l'emboutissage d'une telle tôle revêtue, on observe fréquemment un effritement du revêtement, ou "poudrage", qui provoque un encrassement des outils de mise en forme et une diminution de la protection apportée à la tôle par le revêtement.When stamping such a coated sheet, there is frequently a crumbling of the coating, or "dusting", which causes fouling of the shaping tools and a reduction in the protection provided to the sheet by the coating.

Lors de certaines opérations de mise en forme de ladite tôle, notamment de pliage, on observe parfois également un décollage d'une partie du revêtement, notamment par délamination dans l'épaisseur même du revêtement, ou de la couche déposée.During certain operations for shaping said sheet, in particular for folding, there is sometimes also a peeling off of part of the coating, in particular by delamination in the very thickness of the coating, or of the deposited layer.

Par ailleurs, une telle tôle revêtue par électrodéposition d'une couche d'alliage métallique puis peinte, notamment par cataphorèse, ne présente pas au test de gravillonnage une résistance suffisante, notamment pour des applications automobiles ; le test de gravillonnage consiste à projeter sur la tôle peinte des gravillons solides et à évaluer la résistance au gravillonnage par exemple en comptant le nombre d'impacts sur la tôle où la peinture a été arrachée ; après le test de gravillonnage d'une telle tôle peinte, on observe en effet des écaillages nombreux de peinture et on constate que l'arrachement des écailles de peinture se produit en fait dans l'épaisseur du revêtement ou de la couche électrodéposé.Furthermore, such a sheet coated by electrodeposition with a layer of metal alloy and then painted, in particular by cataphoresis, does not exhibit sufficient resistance to the gravel test, in particular for automotive applications; the gravel test consists of projecting solid gravel onto the painted sheet and evaluating the resistance to gravel, for example by counting the number of impacts on the sheet where the paint has been torn off; after the graveling test of such a painted sheet metal, numerous flaking of paint is observed and it is found that the tearing off of the paint flakes actually occurs in the thickness of the coating or of the electrodeposited layer.

Pour éviter ces problèmes au moment de la mise en forme de telles tôles, il est possible d'améliorer la lubrification des outils de mise en forme.To avoid these problems when forming such sheets, it is possible to improve the lubrication of the forming tools.

Pour améliorer la résistance au gravillonnage de telles tôles qui sont peintes, il est possible d'augmenter l'épaisseur de la couche de peinture.To improve the gravel resistance of such sheets which are painted, it is possible to increase the thickness of the paint layer.

Néanmoins, de telles solutions rendent plus complexes et plus coûteuses les opérations de mise en forme et de mise en peinture de ces tôles.However, such solutions make the shaping and painting operations of these sheets more complex and more expensive.

L'invention a pour but d'améliorer la qualité, notamment la résistance mécanique, des revêtements d'alliages métalliques déposés en continu par électrodéposition sur des bandes métalliques.The object of the invention is to improve the quality, in particular the strength mechanical, coatings of metal alloys deposited continuously by electrodeposition on metal strips.

L'invention a donc également pour but de limiter les inconvénients précités concernant la mise en forme et la mise en peinture des bandes ou des tôles métalliques revêtues d'alliage.The invention therefore also aims to limit the aforementioned drawbacks concerning the shaping and painting of the metal strips or sheets coated with alloy.

L'invention a pour objet une cellule d'électrodéposition pour le revêtement en continu d'une bande métallique, notamment par une couche d'alliage métallique, comprenant une cuve d'électrolyse contenant un bain d'électrodéposition, au moins une anode immergée dans ledit bain et présentant une surface active délimitée par des rebords, des moyens pour faire défiler la bande dans le bain face à ladite surface active d'un rebord de ladite surface à un autre rebord opposé de la même surface, lesdits moyens définissant un chemin de défilement de bande, et des moyens pour faire passer un courant électrique entre ladite anode et ladite bande en défilement servant de cathode, caractérisée en ce que la dite surface active de chaque anode immergée est bordée sur chacun desdits deux rebords opposés par un masque présentant, le long dudit rebord correspondant et face audit chemin de défilement, une surface électriquement isolante, plus proche dudit chemin de défilement que ledit rebord, ledit masque débordant vers l'extérieur de ladite surface active d'anode d'une largeur dite de débordement, mesurée le long de la direction de défilement, au moins égale à la distance qui sépare ledit rebord dudit chemin de défilement, et ledit masque recouvrant le bord de ladite surface active d'anode sur une largeur dite de recouvrement, mesurée le long de la direction de défilement, inférieure à la distance qui sépare ledit rebord dudit chemin de défilement.The subject of the invention is an electroplating cell for the continuous coating of a metal strip, in particular with a layer of metallic alloy, comprising an electrolysis tank containing an electroplating bath, at least one anode immersed in said bath and having an active surface delimited by edges, means for passing the strip in the bath opposite said active surface from one edge of said surface to another opposite edge of the same surface, said means defining a path of strip running, and means for passing an electric current between said anode and said running strip serving as a cathode, characterized in that said active surface of each submerged anode is bordered on each of said two opposite edges by a mask having, along said corresponding edge and facing said travel path, an electrically insulating surface, closer to said travel path that said rim, said mask projecting towards the outside of said active anode surface with a width called overflow, measured along the direction of travel, at least equal to the distance which separates said edge from said travel path, and said mask covering the edge of said active anode surface over a width known as covering, measured along the direction of travel, less than the distance which separates said edge from said travel path.

L'invention peut également présenter une ou plusieurs des caractéristiques suivantes :

  • la distance qui sépare chaque masque bordant un rebord de surface active d'anode, du chemin de défilement de bande est inférieure à 0,5 fois la distance qui sépare ledit rebord du chemin de défilement de bande,
  • ledit masque est en forme de panneau plan et intégralement construit en un matériau électriquement isolant,
  • ladite cellule est de type radial,
  • lesdites anodes sont solubles et/ou ledit bain d'électrodéposition est à base d'anions chlorures,
The invention may also have one or more of the following characteristics:
  • the distance separating each mask bordering an edge of the active anode surface from the strip running path is less than 0.5 times the distance separating said edge from the strip running path,
  • said mask is in the form of a flat panel and entirely constructed of an electrically insulating material,
  • said cell is of the radial type,
  • said anodes are soluble and / or said electroplating bath is based on chloride anions,

L'invention a également pour objet une installation d'électrodéposition pour le revêtement en continu d'une bande métallique, notamment par une couche d'alliage métallique, comprenant une succession en cascade de cellules selon l'invention.The invention also relates to an electroplating installation for the continuous coating of a metal strip, in particular with a layer of metallic alloy, comprising a cascade succession of cells according to the invention.

L'invention a également pour objet l'utilisation de cellules d'électrodéposition selon l'invention pour le revêtement en continu de bandes métalliques par une couche d'alliage métallique.The invention also relates to the use of electroplating cells according to the invention for the continuous coating of metal strips with a layer of metal alloy.

Dans ce cas, l'invention peut également présenter une ou plusieurs des caractéristiques suivantes :

  • ledit alliage métallique est à base de zinc,
  • la teneur pondérale en zinc dudit alliage est supérieure à 10%.
In this case, the invention may also have one or more of the following characteristics:
  • said metal alloy is based on zinc,
  • the zinc content by weight of said alloy is greater than 10%.

L'invention a encore pour objet un procédé de revêtement d'une bande métallique par électrodéposition d'un alliage métallique, notamment à base de zinc, à l'aide d'une installation comprenant plusieurs cellules selon l'invention disposées en cascade dans lequel on fait défiler ladite bande successivement dans lesdites cellules de l'installation, on fait circuler un courant électrique entre les anodes des cellules et ladite bande en défilement, caractérisée en ce que la vitesse de défilement de ladite bande dans l'installation est supérieure à 50 m/minute et/ou la densité du courant électrique circulant entre les anodes des cellules et ladite bande est supérieure à 50 A/dm2.The subject of the invention is also a method of coating a metal strip by electrodeposition of a metal alloy, in particular based on zinc, using an installation comprising several cells according to the invention arranged in cascade in which said strip is passed successively through said cells of the installation, an electric current is circulated between the anodes of the cells and said moving strip, characterized in that the running speed of said strip in the installation is greater than 50 m / minute and / or the density of the electric current flowing between the anodes of the cells and said strip is greater than 50 A / dm2.

L'invention sera mieux comprise à la lecture de la description qui va suivre, donnée à titre d'exemple et en référence aux dessins annexés, sur lesquels :

  • la figure 1 est un schéma en coupe d'une cellule plane d'électrodéposition selon l'invention,
  • la figure 2 est un schéma en coupe d'une cellule radiale d'électrodéposition selon l'invention.
The invention will be better understood on reading the description which follows, given by way of example and with reference to the appended drawings, in which:
  • FIG. 1 is a diagram in section of a plane electrodeposition cell according to the invention,
  • Figure 2 is a sectional diagram of a radial electroplating cell according to the invention.

L'installation d'électrodéposition comprend plusieurs cellules d'électrodéposition identiques disposées en cascade.The plating installation comprises several identical plating cells arranged in cascade.

La première cellule de l'installation est représentée à la figure 1, désignée dans son ensemble par la référence 1, et comprend une cuve d'électrolyse 2 contenant un bain d'électrodéposition S, des moyens assurant le défilement d'une bande métallique B dans le bain S et définissant un chemin de défilement de bande, et, positionnés successivement sous le chemin de défilement de bande et face à lui, deux anodes 3 ; la cellule 1 comprend également des moyens de circulation d'un courant électrique entre lesdites anodes 3 et la bande B en défilement servant de cathode, qui ne sont pas représentés ici.The first cell of the installation is represented in FIG. 1, designated as a whole by the reference 1, and comprises an electrolysis tank 2 containing an electroplating bath S, means ensuring the movement of a metal strip B in the bath S and defining a strip running path, and, positioned successively under the strip running path and facing it, two anodes 3; cell 1 also comprises means for circulating an electric current between said anodes 3 and strip B running as cathode, which are not shown here.

Sans se départir de la présente invention, la cellule d'électrodéposition peut comporter une seule anode ou plus de deux anodes successives.Without departing from the present invention, the electroplating cell can comprise a single anode or more than two successive anodes.

La nature des anodes, la nature, la température et la composition du bain d'électrodéposition seront précisés ultérieurement dans l'exposé de la mise en oeuvre de la cellule selon l'invention.The nature of the anodes, the nature, the temperature and the composition of the bath electrodeposition will be specified later in the description of the implementation of the cell according to the invention.

Les moyens de défilement comprennent des cylindres de support de bande à axes parallèles, à savoir deux cylindres d'entrée de bande 5, 6 , deux cylindres de sortie de bande 7, 8 et un cylindre intermédiaire 9 de soutien de bande dans la cuve. Du côté de l'entrée comme du côté de la sortie de la cuve, l'un 6, 7 des deux cylindres est immergé, l'autre 5, 8 est émergé ; le cylindre intermédiaire 9 est immergé ; les cylindres émergés 5, 8 sont conducteurs et sont motorisés pour entraîner la bande B en défilement.The running means comprise tape support cylinders with parallel axes, namely two tape entry cylinders 5, 6, two tape exit cylinders 7, 8 and an intermediate cylinder 9 for tape support in the tank. On the inlet side as on the outlet side of the tank, one 6, 7 of the two cylinders is submerged, the other 5, 8 is emerged; the intermediate cylinder 9 is immersed; the emerged cylinders 5, 8 are conductive and are motorized to drive the strip B in movement.

Les trois cylindres 6, 9, 7 immergés dans la cuve d'électrolyse définissent le chemin de défilement de bande dans la cuve d'électrolyse, qui est ici approximativement dans un plan horizontal.The three cylinders 6, 9, 7 immersed in the electrolytic cell define the strip running path in the electrolytic cell, which here is approximately in a horizontal plane.

Les deux anodes 3 sont positionnées chacune entre deux cylindres immergés et présentent chacune une surface active plane 13 placée au dessous du chemin de défilement de bande et orientée parallèlement à lui et vers lui.The two anodes 3 are each positioned between two submerged cylinders and each have a planar active surface 13 placed below the strip running path and oriented parallel to it and towards it.

La distance qui sépare la surface active 13 des anodes 3 du chemin de défilement de bande est généralement comprise entre 0,5 et 10 cm dans une cellule industrielle.The distance between the active surface 13 of the anodes 3 of the strip running path is generally between 0.5 and 10 cm in an industrial cell.

D'une manière connue en elle-même et non décrite ici, les surfaces actives 13 des anodes 3 s'étendent transversalement à la direction de défilement sur toute la largeur de la bande à revêtir. Par ailleurs, les surfaces actives 13 des anodes 3 s'étendent le long de la direction de défilement de bande entre deux rebords opposés 3A, 3B.In a manner known in itself and not described here, the active surfaces 13 of the anodes 3 extend transversely to the direction of travel over the entire width of the strip to be coated. Furthermore, the active surfaces 13 of the anodes 3 extend along the direction of travel of the strip between two opposite edges 3A, 3B.

Au niveau des rebords 3A, 3B, la distance qui sépare la surface active 13 des anodes 3 du chemin de défilement de bande est couramment de 3 cm environ.At the edges 3A, 3B, the distance between the active surface 13 of the anodes 3 of the strip running path is commonly about 3 cm.

Selon l'invention, chaque anode 3 est bordée, le long de ces deux rebords opposés 3A, 3B, par deux masques 4A, 4B en forme de panneaux plans étroits.According to the invention, each anode 3 is bordered, along these two opposite edges 3A, 3B, by two masks 4A, 4B in the form of narrow flat panels.

Chaque masque 4A, 4B en forme de panneau s'étend le long d'un rebord correspondant 3A, 3B de la surface active d'anode 3 et est disposé dans un plan approximativement parallèle au chemin de défilement de bande.Each panel-shaped mask 4A, 4B extends along a corresponding rim 3A, 3B of the active anode surface 3 and is arranged in a plane approximately parallel to the strip running path.

Les masques sont en matériau électriquement isolant, de préférence en matériau composite ou en matière plastique.The masks are made of electrically insulating material, preferably of composite material or plastic.

Les masques 4A, 4B, qui longent chacun un rebord 3A, 3B de surface active d'anode, sont toujours plus proches du chemin de défilement de bande que les anodes. De préférence, la distance qui sépare un masque 4A, 4B du chemin de défilement de bande est inférieure à 0,5 fois la distance inter-électrode, c'est à dire celle qui sépare le rebord correspondant 3A, 3B du même chemin de défilement.The masks 4A, 4B, which each run along an edge 3A, 3B of the active anode surface, are always closer to the strip running path than the anodes. Preferably, the distance which separates a mask 4A, 4B from the strip travel path is less than 0.5 times the inter-electrode distance, ie that which separates the corresponding flange 3A, 3B from the same travel path.

Sans se départir de l'invention, les masques peuvent se présenter sous une forme différente de celle d'un panneau plan étroit tout en offrant, face au chemin de défilement et le long d'un rebord de surface active d'anode, une surface de masquage électriquement isolante et plus proche du chemin de défilement que ledit rebord.Without departing from the invention, the masks can be in a form different from that of a narrow flat panel while offering, facing the running path and along an edge of the active anode surface, a surface electrically insulating masking and closer to the running path than said flange.

L'épaisseur des masques 4A, 4B est de préférence largement inférieure à ladite distance inter-électrode, de telle sorte que lesdits masques peuvent être partiellement insérés entre l'anode et le chemin de défilement de bande sous le rebord correspondant 3A, 3B de surface active 13 d'anode.The thickness of the masks 4A, 4B is preferably much less than said inter-electrode distance, so that said masks can be partially inserted between the anode and the strip running path under the corresponding surface rim 3A, 3B active anode 13.

L'épaisseur des masques 4A, 4B est cependant suffisante pour assurer une fonction de masquage électrique entre la surface active 13 d'anode et la bande en défilement servant de cathode.The thickness of the masks 4A, 4B is however sufficient to provide an electrical masking function between the active surface 13 of the anode and the running strip serving as the cathode.

Ainsi, l'épaisseur des masques est couramment de l'ordre de 1 cm.Thus, the thickness of the masks is commonly of the order of 1 cm.

De préférence, chaque masque 4A, 4B , qui longe un rebord 3A, 3B de surface active d'anode, présente une intersection continue avec la surface abstraite passant par ledit rebord 3A, 3B et orthogonale au chemin de défilement de bande.Preferably, each mask 4A, 4B, which runs along a rim 3A, 3B of active anode surface, has a continuous intersection with the abstract surface passing through said rim 3A, 3B and orthogonal to the strip running path.

Le masque 4A, 4B, en forme de panneau plan étroit, s'étend en largeur de chaque côté de ladite intersection, c'est à dire, recouvrant d'un côté le rebord correspondant 3A, 3B de la surface active d'anode et débordant largement de l'autre côté vers l'extérieur de ladite surface active.The mask 4A, 4B, in the form of a narrow flat panel, extends in width on each side of said intersection, that is to say, covering on one side the corresponding rim 3A, 3B of the active anode surface and largely protruding from the other side towards the outside of said active surface.

La largeur dite de recouvrement, mesurée le long de la direction de défilement, est inférieure à la distance qui sépare ledit rebord dudit chemin de défilement.The so-called overlap width, measured along the direction of travel, is less than the distance between said edge of said travel path.

Ainsi, la largeur de recouvrement du masque 4A, 4B par rapport au rebord 3A, 3B correspondant d'anode 3 est couramment inférieure à 1 cm.Thus, the overlap width of the mask 4A, 4B relative to the rim 3A, 3B corresponding to the anode 3 is commonly less than 1 cm.

La largeur de débordement du masque 4A, 4B par rapport au rebord 3A, 3B correspondant d'anode 3 est supérieure ou égale à la distance inter-électrode, au niveau dudit rebord.The overflow width of the mask 4A, 4B relative to the corresponding rim 3A, 3B of anode 3 is greater than or equal to the inter-electrode distance, at the level of said rim.

Selon la description ci-dessus, chaque anode 3 est ainsi bordée par deux masques 4A, 4B le long de deux rebords opposés 3A, 3B ; selon une variante de l'invention, deux masques, qui se suivent immédiatement le long du chemin de défilement de bande et qui encadrent deux anodes successives, peuvent être jointifs et ne former qu'un seul panneau plan. Un même masque peut ainsi servir à border deux anodes successives.According to the above description, each anode 3 is thus bordered by two masks 4A, 4B along two opposite edges 3A, 3B; according to a variant of the invention, two masks, which immediately follow one another along the strip running path and which frame two successive anodes, can be contiguous and form only one flat panel. The same mask can thus be used to border two successive anodes.

Les moyens de circulation d'un courant électrique entre les anodes 3 et la bande en défilement servant de cathode comprennent les deux cylindres émergés 5, 8 qui sont conducteurs, sont connus par ailleurs en eux mêmes et ne sont pas décrits ici en détail.The means for circulating an electric current between the anodes 3 and the running strip serving as the cathode comprise the two emerged cylinders 5, 8 which are conductive, are known in themselves and are not described here in detail.

L'invention s'applique à toutes les géométries de cellule d'électrodéposition, notamment aux cellules radiales ; on a ainsi représenté à la figure 2 un schéma en coupe d'une cellule radiale, désignée dans son ensemble par la référence 1', comprenant une cuve 2' contenant un bain d'électrodéposition S', des moyens de défilement de bande comprenant deux cylindres émergés conducteurs 5', 8' et un cylindre partiellement immergé 9' dont la surface définit le chemin de défilement de bande, deux anodes immergées 3' en forme d'arc de cercle faisant face à la partie immergée dudit cylindre 9', et trois masques 10, 11 et 12.The invention applies to all geometries of electroplating cell, in particular to radial cells; FIG. 2 thus represents a cross-sectional diagram of a radial cell, designated as a whole by the reference 1 ′, comprising a tank 2 ′ containing an electroplating bath S ′, strip running means comprising two emerging conductive cylinders 5 ', 8' and a partially submerged cylinder 9 'whose surface defines the strip running path, two submerged anodes 3' in the shape of an arc of a circle facing the submerged part of said cylinder 9 ', and three masks 10, 11 and 12.

Le premier masque 10 se situe au niveau du rebord d'anode qui voit la bande rentrer dans le bain et le troisième masque 12 se situe au niveau du dernier rebord d'anode qui voit la bande sortir du bain.The first mask 10 is located at the level of the anode rim which sees the strip re-entering the bath and the third mask 12 is located at the level of the last anode rim which sees the strip exiting the bath.

Dans la configuration particulière représentée à la figure 2, le premier et le troisième masques peuvent présenter une partie émergée.In the particular configuration represented in FIG. 2, the first and the third masks may have an emerged part.

Le deuxième masque 11 est un masque intermédiaire qui s'étend entre les deux anodes 3' et borde donc à la fois un des rebords de chaque anode 3'.The second mask 11 is an intermediate mask which extends between the two anodes 3 'and therefore borders both of the edges of each anode 3'.

Selon une variante de l'invention, lorsque la cellule d'électrodéposition est dotée de dispositifs d'injection de bain d'électrodéposition, en particulier de rampes d'éjecteurs également positionnés au niveau de rebords d'anodes et débouchant dans l'intervalle séparant les anodes du chemin de défilement de bande, les masques peuvent être supportés par lesdites rampes.According to a variant of the invention, when the electrodeposition cell is provided with electrodeposition bath injection devices, in particular ejector ramps also positioned at the edge of the anodes and opening into the interval separating the anodes of the strip running path, the masks can be supported by said ramps.

Dans le cas où une desdites rampes présente un seul éjecteur s'étendant sur toute la largeur du chemin de défilement de bande, ledit éjecteur peut avantageusement servir de masque à condition d'être électriquement isolant et la surface de masquage qui fait face au chemin de défilement de bande n'est pas forcément plane.In the case where one of said ramps has a single ejector extending over the entire width of the strip running path, said ejector can advantageously serve as a mask provided that it is electrically insulating and the masking surface which faces the path of tape scrolling is not necessarily flat.

On va maintenant décrire la mise en oeuvre de l'installation d'électrodéposition comprenant une succession de cellules d'électrodéposition 1 selon l'invention pour procéder au revêtement d'une couche d'alliage de zinc à la surface d'une bande d'acier B.We will now describe the implementation of the electroplating installation comprising a succession of electroplating cells 1 according to the invention for coating a layer of zinc alloy on the surface of a strip of steel B.

Chaque cellule de l'installation contribue à la formation d'une portion de la couche de revêtement, ou "sous-couche" et l'empilement des sous-couches forme la couche d'alliage.Each cell of the installation contributes to the formation of a portion of the coating layer, or "sublayer" and the stacking of the sublayers forms the alloy layer.

Les cellules 1 de l'installation sont dotées d'anodes solubles en zinc.The cells 1 of the installation have soluble zinc anodes.

On remplit les cuves 2 des différentes cellules 1 d'un bain d'électrodéposition S à base d'anions chlorures et contenant des cations de zinc et des éléments d'alliage dans des proportions et des concentrations connues en elles-mêmes pour obtenir ladite couche d'alliage à la composition souhaitée.The tanks 2 of the different cells 1 are filled with an electroplating bath S based on chloride anions and containing zinc cations and alloying elements in proportions and concentrations known in themselves to obtain said layer of alloy with the desired composition.

De préférence, lesdits éléments d'alliage sont choisis parmi le nickel, le fer ou le cobalt.Preferably, said alloying elements are chosen from nickel, iron or cobalt.

A l'aide des moyens de défilement de bande, on fait défiler la bande B successivement dans chacune des cellules de l'installation.Using the tape scrolling means, the tape B is scrolled successively in each of the cells of the installation.

A l'aide des moyens de circulation du courant électrique, on fait passer un courant électrique entre les anodes des différentes cellules et la bande d'acier B servant de cathode.Using the means for circulating the electric current, an electric current is passed between the anodes of the different cells and the steel strip B serving as the cathode.

La vitesse de défilement de bande et la densité de courant électrique des différentes cellules sont ajustées d'une manière connue en elle-même, en particulier en fonction de l'épaisseur de la couche d'électrodéposition souhaitée.The tape running speed and the electric current density of the different cells are adjusted in a manner known per se, in particular as a function of the thickness of the desired plating layer.

De préférence, la vitesse de défilement de bande est supérieure à 50 m/min.Preferably, the tape running speed is greater than 50 m / min.

De préférence, la densité de courant est supérieure à 50 A/dm2.Preferably, the current density is greater than 50 A / dm2.

La bande d'acier B ressort alors de l'installation revêtue d'une couche d'alliage.The steel strip B then emerges from the installation coated with a layer of alloy.

La demanderesse a constaté avec surprise qu'on ne constatait que très peu d'effritement du revêtement électrodéposé en mettant en forme ultérieurement la bande d'acier revêtue, ou les tôles découpées dans cette bande, en comparaison de l'effritement qu'on observe sur des tôles revêtues d'alliage d'une manière classique.The Applicant noted with surprise that there was very little crumbling of the electrodeposited coating by subsequently shaping the coated steel strip, or the sheets cut from this strip, in comparison with the crumbling which is observed. on sheets coated with alloy in a conventional manner.

On limite ainsi l'effritement même pour des déformations importantes des tôles revêtues selon l'invention.This limits crumbling even for significant deformations of the coated sheets according to the invention.

La demanderesse a constaté également avec surprise que ladite bande peinte, notamment par cataphorèse, résistait beaucoup mieux au test de gravillonnage qu'une tôle revêtue de manière classique de la même couche d'alliage et peinte de la même façon.The Applicant has also surprisingly found that said painted strip, in particular by cataphoresis, withstood the gravel test much better than a sheet conventionally coated with the same layer of alloy and painted in the same way.

Selon une variante de l'invention, on équipe les cellules de l'installation d'électrodéposition d'électrodes insolubles et on remplit les cuves des cellules d'un bain d'électrolyse à base d'autres anions que d'ions chlorures, notamment d'ions sulfates.According to a variant of the invention, the cells of the electrodeposition installation are equipped with insoluble electrodes and the cells of the cells are filled with an electrolysis bath based on anions other than chloride ions, in particular of sulfate ions.

Selon une autre variante de l'invention, la couche électrodéposée est un alliage métallique basé sur d'autres métaux que le zinc, notamment à base d'étain et de plomb, ou à base de fer et de nickel, ou à base de cuivre et de nickel. La composition du bain d'électrodéposition est adaptée d'une manière connue en elle-même au type d'alliage du revêtement à déposer.According to another variant of the invention, the electrodeposited layer is a metal alloy based on metals other than zinc, in particular based of tin and lead, or based on iron and nickel, or based on copper and nickel. The composition of the electroplating bath is adapted in a manner known per se to the type of alloy of the coating to be deposited.

On peut mettre en oeuvre l'installation d'électrodéposition décrite ci-dessus pour procéder au revêtement de bande d'acier ou d'autres bandes métalliques, notamment de bandes en acier inoxydable.The above-described electrodeposition installation can be used to coat steel strip or other metal strips, in particular stainless steel strips.

Globalement, la demanderesse a constaté qu'en utilisant une installation comprenant une succession de cellules selon l'invention pour revêtir en continu une bande métallique, notamment d'acier, d'une couche d'alliage, notamment à base de zinc, on obtenait avantageusement un revêtement présentant dans son épaisseur une grande homogénéité, notamment de composition, et d'excellentes propriétés mécaniques, notamment une résistance à la délamination.Overall, the Applicant has found that by using an installation comprising a succession of cells according to the invention for continuously coating a metal strip, in particular of steel, with a layer of alloy, notably based on zinc, one obtains advantageously a coating having in its thickness a great homogeneity, in particular of composition, and excellent mechanical properties, in particular a resistance to delamination.

Sans s'estimer liée par aucune théorie, la demanderesse considère que les masques bordant les anodes des cellules d'électrodéposition de l'installation provoquent une variation brutale de la densité de courant à l'entrée et à la sortie des différentes anodes de l'installation, ce qui permet d'assurer le dépôt sous des conditions de densité de courant plus homogènes qui garantissent une composition d'alliage constante sur l'épaisseur de la couche .Without considering itself bound by any theory, the applicant considers that the masks bordering the anodes of the electroplating cells of the installation cause a sudden variation in the current density at the input and at the output of the various anodes of the installation, which makes it possible to ensure deposition under more homogeneous current density conditions which guarantee a constant alloy composition over the thickness of the layer.

Les exemples suivants illustrent l'invention :The following examples illustrate the invention:

Essai 1 : Test 1 :

Cet essai a pour but de préparer un revêtement d'alliage de zinc sur une bande d'acier dans des cellules d'électrodéposition selon l'invention.The purpose of this test is to prepare a coating of zinc alloy on a steel strip in electroplating cells according to the invention.

L'installation d'électrodéposition comporte une succession de cellules radiales 1' selon l'invention, du type précédemment décrit et représenté à la figure 2.The electrodeposition installation comprises a succession of radial cells 1 ′ according to the invention, of the type previously described and shown in FIG. 2.

Le cylindre partiellement immergé 9' qui définit le chemin de défilement de bande dans la cellule présente une largeur de 2 m et un diamètre de 2 m.The partially submerged cylinder 9 'which defines the strip running path in the cell has a width of 2 m and a diameter of 2 m.

Les deux anodes 3' sont en zinc et solubles. La distance moyenne séparant les anodes et ledit cylindre 9' est de 3 cm.The two 3 'anodes are made of zinc and soluble. The average distance between the anodes and said cylinder 9 'is 3 cm.

Les trois masques 10, 11 et 12 sont disposés à environ 1 cm dudit cylindre 9' et pénètrent à peine, sur une profondeur de moins de 1 cm, dans l'intervalle qui sépare les anodes 3' dudit cylindre 9'.The three masks 10, 11 and 12 are arranged about 1 cm from said cylinder 9 'and barely penetrate, to a depth of less than 1 cm, in the interval which separates the anodes 3' from said cylinder 9 '.

Les trois masques 10, 11, 12 qui bordent les deux anodes sont des panneaux plans en polypropylène de 2 m de long, environ 20 cm de large et de 1 cm d'épaisseur.The three masks 10, 11, 12 which border the two anodes are flat polypropylene panels 2 m long, about 20 cm wide and 1 cm thick.

Le bain d'électrodéposition contient :

  • 140 g/l d'ions de zinc,
  • 16 g/l d'ions de nickel,
  • 300 g/l d'ions chlorure.
The plating bath contains:
  • 140 g / l of zinc ions,
  • 16 g / l of nickel ions,
  • 300 g / l of chloride ions.

La température du bain est maintenue à 57°C et le pH du bain est maintenu à une valeur de environ 4,5 par des additions d'acide chlorhydrique.The temperature of the bath is maintained at 57 ° C. and the pH of the bath is maintained at a value of approximately 4.5 by additions of hydrochloric acid.

La bande à revêtir est en acier, présente une largeur de 1,5 m et une épaisseur de 1 mm.The strip to be coated is made of steel, has a width of 1.5 m and a thickness of 1 mm.

On fait défiler la bande dans l'installation à une vitesse de 100 m/min. et on fait passer un courant électrique entre les anodes et la bande de 100 A/dm2.The strip is scrolled through the installation at a speed of 100 m / min. and an electric current is passed between the anodes and the strip of 100 A / dm2.

On obtient une bande revêtue sur une face d'une couche d'alliage de zinc contenant 12% en poids de nickel et d'une épaisseur d'environ 4 micromètres.A strip coated on one face with a layer of zinc alloy containing 12% by weight of nickel and with a thickness of approximately 4 micrometers is obtained.

Essai 2 : Test 2 :

Cet essai a pour but d'indiquer qu'une tôle revêtue selon l'invention d'une couche d'alliage peut être mise en forme sans risque de dégradation sensible de son revêtement.The purpose of this test is to indicate that a sheet coated according to the invention with an alloy layer can be shaped without risk of appreciable degradation of its coating.

A partir d'une même bande d'acier, on prépare trois flans de tôles de mêmes dimensions A, B, C revêtues selon trois procédés différents d'une même couche d'épaisseur 4 micromètres d'alliage zinc-nickel à 12% pondéral en nickel.From the same steel strip, three blanks of sheets of the same dimensions A, B, C are prepared, coated according to three different processes with the same layer of thickness 4 micrometers of zinc-nickel alloy at 12% by weight nickel.

Le revêtement du flan de tôle A a été préparé en discontinu d'une manière connue en elle-même en immergeant et en maintenant ledit flan de tôle à revêtir dans une cellule d'électrodéposition face à une anode, sans défilement, et en faisant passer un courant électrique entre ladite anode et le flan de tôle servant de cathode.The coating of the sheet blank A was prepared discontinuously in a manner known per se by immersing and maintaining the said sheet blank to be coated in an electroplating cell facing an anode, without scrolling, and by passing an electric current between said anode and the sheet blank serving as cathode.

Le flan de tôle B est découpé dans une bande d'acier revêtue en continu selon l'art antérieur, c'est à dire par défilement de ladite bande dans des cellules d'électrodéposition qui ne sont pas dotées de masques de rebord d'anodes.The sheet blank B is cut from a strip of steel coated continuously according to the prior art, that is to say by scrolling of said strip in electroplating cells which are not provided with anode edge masks .

Le flan de tôle C est découpé dans une bande d'acier revêtue en continu selon l'essai n°1 ci-dessus.The sheet blank C is cut from a continuously coated steel strip according to test No. 1 above.

On procède ensuite dans les mêmes conditions à l'emboutissage des flans de tôles A, B, C et on mesure, à l'issue de l'opération d'emboutissage, la perte de poids de chaque flan de tôle rapportée à la surface du revêtement. Le résultat de la mesure est un indicateur proportionnel à l'effritement ou au "poudrage" du revêtement.Then, under the same conditions, the sheet blanks A, B, C are stamped and, after the stamping operation, the weight loss of each sheet blank compared to the surface of the surface is measured. coating. The result of the measurement is an indicator proportional to the crumbling or "dusting" of the coating.

On obtient les résultats suivants de perte de poids par unité de surface : flan A : 0,3 g/m2 - flan B : 1,1 g/m2 - flan C : 0,4 g/m2.The following weight loss results are obtained per unit area: blank A: 0.3 g / m2 - blank B: 1.1 g / m2 - blank C: 0.4 g / m2.

Ainsi, le revêtement d'alliage préparé en continu sur une tôle d'acier dans des cellules d'électrodéposition selon l'invention présente une excellente résistance à l'effritement et au "poudrage".Thus, the alloy coating continuously prepared on a steel sheet in electroplating cells according to the invention has excellent resistance to crumbling and "dusting".

Essai n°3 : Test # 3 :

Cet essai a pour but d'indiquer qu'une tôle peinte préalablement revêtue selon l'invention d'une couche d'alliage résiste particulièrement bien au test de gravillonnage.The purpose of this test is to indicate that a painted sheet metal previously coated according to the invention with an alloy layer withstands the gravel test particularly well.

D'une manière connue en elle-même, on peint par cataphorèse et dans les mêmes conditions chaque flan de tôle A, B, C de l'essai n°2. D'une manière classique, l'épaisseur de la couche de peinture est d'environ 100 micromètres.In a manner known per se, each sheet blank A, B, C of test No. 2 is painted by cataphoresis and under the same conditions. Conventionally, the thickness of the paint layer is approximately 100 micrometers.

On soumet ensuite chaque flan de tôle A, B, C au même test de gravillonnage, qui consiste à projeter pendant un temps prédéterminé des gravillons sur les flans de tôle à tester.Each sheet blank A, B, C is then subjected to the same gravel test, which consists in projecting gravel for a predetermined time on the sheet blanks to be tested.

Selon la résistance du revêtement, les impacts de gravillons sur les flans de tôle peinte A, B, C, provoquent ou non des arrachements de la peinture et du revêtement.Depending on the resistance of the coating, the impact of gravel on the blanks of painted sheet A, B, C, may or may not cause the paint and coating to tear off.

On mesure d'une manière connue en elle-même et dans une échelle de O à 7 la proportion de surface peinte qui a été arrachée lors du test, O signifiant l'absence d'arrachement et une excellente résistance au gravillonnage et 7 signifiant un arrachement très important et une mauvaise résistance au gravillonnage.In a manner known per se and on a scale of O to 7, the proportion of painted surface which has been torn off during the test is measured, O signifying the absence of tearing and excellent resistance to graveling and 7 signifying a very large pullout and poor resistance to graveling.

Les résultats des mesures de résistance au gravillonnage sont les suivants : flan A : 2 - flan B : 4 - flan C : 2.The results of the gravel resistance measurements are as follows: blank A: 2 - blank B: 4 - blank C: 2.

Par l'observation des points d'impact, on constate que l'arrachement de peinture sur le flan B entraîne souvent, par délamination, une partie du revêtement d'alliage alors que l'arrachement de peinture sur les flans A et B n'entraîne généralement pas le revêtement. Cette observation permet d'attribuer les meilleures performances réalisées sur les flans A et C au revêtement d'alliage lui-même.By observing the points of impact, it can be seen that the tearing of paint on the blank B often involves, by delamination, part of the coating of alloy while the tearing of paint on the blanks A and B does not generally does not result in coating. This observation makes it possible to attribute the best performances achieved on the blanks A and C to the alloy coating itself.

On constate donc une amélioration très sensible de la résistance au gravillonnage de tôles peintes préalablement revêtue d'alliage en continu selon l'invention par rapport à celle de tôles peintes de la même façon et préalablement revêtues en continu de la même couche d'alliage, mais d'une manière classique, notamment à l'aide de cellules d'électrodéposition ne comportant pas de masques.There is therefore a very significant improvement in the resistance to graveling of painted sheets previously coated with continuous alloy according to the invention compared to that of sheets painted in the same way and previously coated continuously with the same alloy layer, but in a conventional manner, in particular with the aid of electroplating cells not comprising masks.

Claims (10)

  1. Electroplating cell (1) for the continuous coating of a metal strip (B), especially with a layer of metal alloy, comprising an electrolysis tank (2) containing a plating solution (S), at least one anode (3) immersed in the said solution and having an active surface (13) delimited by edges, means for making the strip run through the solution (S) in front of the said active surface from one edge (3A) of the said active surface to another opposite edge (3B) of the same surface, the said means defining a strip running path, and means for making an electrical current pass between the said anode (3) and the said running strip (B) serving as cathode, characterized in that the said active surface (13) of each immersed anode (3) is bordered on each of the said two opposite edges (3A, 3B) by a mask (4A, 4B) having, along the said corresponding edge (3A, 3B) and in front of the said running path, an electrically insulating surface closer to the said running path than the said edge (3A, 3B), the said mask (4A, 4B) overhanging, towards the outside, the said anode active surface (13) by an amount of overhang, measured along the running direction, at least equal to the distance which separates the said edge (3A, 3B) from the said running path, and the said mask (4A, 4B) overlapping the edge (3A, 3B) of the said anode active surface (13) by an amount termed the overlap, measured along the running direction, less than the distance which separates the said edge from the said running path.
  2. Electroplating cell according to Claim 1, characterized in that the distance which separates each mask (4A, 4B), bordering an edge (3A, 3B) of the active surface (13) of the anode (3), from the strip running path is less than 0.5 times the distance which separates the said edge (3A, 3B) from the strip running path.
  3. Electroplating cell according to either of Claims 1 and 2, characterized in that the said mask (4A, 4B) is in the form of a plane panel made from electrically insulating material.
  4. Electroplating cell according to any one of Claims 1 to 3, characterized in that the cell is of the radial type.
  5. Electroplating cell according to any one of Claims 1 to 4, characterized in that the said anodes (3) are soluble and/or in that the said plating solution (S) is based on chloride anions.
  6. Electroplating installation for the continuous coating of a metal strip (B), especially with a layer of metal alloy, comprising a cascaded succession of cells (1) according to any one of Claims 1 to 5.
  7. Use of an electroplating cell according to any one of Claims 1 to 5 or of an electroplating installation according to Claim 6 for the continuous coating of metal strips (B) with a layer of metal alloy.
  8. Use according to Claim 7, characterized in that the said alloy is a zinc-based alloy.
  9. Use according to Claim 8, characterized in that the zinc content by weight of the said alloy is greater than 10%.
  10. Process for coating a metal strip (B) by electroplating with a metal alloy, especially a zinc-based alloy, using an installation comprising several cells (1) according to any one of Claims 1 to 5, these being arranged in cascade, in which process the said strip (B) is made to run successively through the said cells (1) of the installation and an electrical current is made to flow between the anodes (3) of the cells and the said running strip (B), characterized in that the running speed of the said strip (B) in the installation is greater than 50 m/minute and/or the density of the electrical current flowing between the anodes (3) of the cells and the said strip (B) is greater than 50 A/dm2.
EP95401908A 1994-09-29 1995-08-18 Cell for continuous electrodeposition of metal alloys Expired - Lifetime EP0704558B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9411610A FR2725215B1 (en) 1994-09-29 1994-09-29 CONTINUOUS ELECTRODEPOSITION CELL OF METAL ALLOYS
FR9411610 1994-09-29

Publications (2)

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EP0704558A1 EP0704558A1 (en) 1996-04-03
EP0704558B1 true EP0704558B1 (en) 1997-11-19

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EP95401908A Expired - Lifetime EP0704558B1 (en) 1994-09-29 1995-08-18 Cell for continuous electrodeposition of metal alloys

Country Status (8)

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US (1) US5582708A (en)
EP (1) EP0704558B1 (en)
JP (1) JP3398776B2 (en)
KR (1) KR960010906A (en)
AT (1) ATE160389T1 (en)
DE (1) DE69501073T2 (en)
ES (1) ES2112025T3 (en)
FR (1) FR2725215B1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19717489B4 (en) * 1997-04-25 2008-04-10 Sms Demag Ag Arrangement for the electrogalvanic metal coating of a strip
US6174425B1 (en) * 1997-05-14 2001-01-16 Motorola, Inc. Process for depositing a layer of material over a substrate
KR19990064747A (en) * 1999-05-06 1999-08-05 이종구 Manufacturing method of Ni-Fe alloy thin plate and its apparatus
US6231743B1 (en) 2000-01-03 2001-05-15 Motorola, Inc. Method for forming a semiconductor device
CA2551273A1 (en) * 2003-12-23 2005-07-14 Corus Staal Bv Improved metal strip electroplating
ES2818224B2 (en) 2019-10-07 2021-11-16 Pueo Felix Prado INSTALLATION OF ELECTRO-DEPOSITION WITH ACTIVE INTER-CELL BARS

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3692639A (en) * 1969-10-13 1972-09-19 Center Scient & Applied Res Multiplication of metal surface,by electroplating or anodic dissolution
US4128459A (en) * 1977-11-25 1978-12-05 Allied Chemical Corporation Continuous electroplating of alloy onto metallic strip
JPS5841358B2 (en) * 1980-01-12 1983-09-12 株式会社小糸製作所 plating device
JPS58181894A (en) * 1982-04-14 1983-10-24 Nippon Kokan Kk <Nkk> Preparation of steel plate electroplated with composite fe-zn alloy layers with different kind of compositions
JPS59160000A (en) * 1983-02-28 1984-09-10 Kawasaki Steel Corp Device for preventing edge overcoating in continuous electroplating of strip
JPS60121293A (en) * 1983-12-03 1985-06-28 Kawasaki Steel Corp Manufacture of zn-fe alloy galvanized steel plate consisting essentially of zn-fe alloy
JPH07116636B2 (en) * 1986-09-26 1995-12-13 川崎製鉄株式会社 Cell with radial type
GB8809750D0 (en) * 1988-04-25 1988-06-02 Beckswift Ltd Electrical apparatus
DE4139066A1 (en) * 1991-11-28 1993-06-03 Hans Josef May DEVICE FOR ELECTROLYTIC METAL DEPOSITION ON METAL BANDS

Also Published As

Publication number Publication date
DE69501073T2 (en) 1998-05-07
US5582708A (en) 1996-12-10
FR2725215B1 (en) 1996-11-22
JPH08209394A (en) 1996-08-13
DE69501073D1 (en) 1998-01-02
ATE160389T1 (en) 1997-12-15
FR2725215A1 (en) 1996-04-05
EP0704558A1 (en) 1996-04-03
ES2112025T3 (en) 1998-03-16
JP3398776B2 (en) 2003-04-21
KR960010906A (en) 1996-04-20

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