EP0410955B1 - Process for one side electroplating of flat workpieces - Google Patents

Process for one side electroplating of flat workpieces Download PDF

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Publication number
EP0410955B1
EP0410955B1 EP90890216A EP90890216A EP0410955B1 EP 0410955 B1 EP0410955 B1 EP 0410955B1 EP 90890216 A EP90890216 A EP 90890216A EP 90890216 A EP90890216 A EP 90890216A EP 0410955 B1 EP0410955 B1 EP 0410955B1
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EP
European Patent Office
Prior art keywords
detachment
electrolyte
coating
cell
chloride
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Expired - Lifetime
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EP90890216A
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German (de)
French (fr)
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EP0410955A1 (en
Inventor
Gerald Dr. Dipl.-Ing. Maresch
Ulrich Krupicka
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Andritz AG
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Andritz AG
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    • 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
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/02—Electroplating of selected surface areas
    • C25D5/028—Electroplating of selected surface areas one side electroplating, e.g. substrate conveyed in a bath with inhibited background plating
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F5/00—Electrolytic stripping of metallic layers or coatings

Definitions

  • the invention relates to a method for the one-sided electrolytic coating of flat workpieces made of steel, in particular steel strip, with a metal or a metal alloy, in particular with a zinc-nickel alloy, whereby after applying a thin layer of the same material that is provided for the one-sided coating is, the one-sided coating is carried out on both sides of the workpiece and finally there is an electrolytic detachment of the thin layer on the side opposite the side to be permanently coated, the workpiece being switched as a central conductor for electrolytic detachment.
  • the object of the invention was therefore to provide a method which avoids the above-mentioned disadvantage of cementation on the uncoated side.
  • a method which is characterized in that an aqueous solution of an alkali metal or alkaline earth metal chloride, preferably sodium or potassium chloride, at a pH of 7 to 12 is used as the electrolyte in the detachment.
  • an alkali metal or alkaline earth metal chloride preferably sodium or potassium chloride
  • the steel strip After passing through the cleaning system 1 in the first cell or in the inlet part 2 into the electroplating system 3, the steel strip is coated on both sides with a zinc-nickel alloy, which is to avoid chemical cementation of the nickel on this side in the other cells.
  • the coating applied first is detached again in a further cell 5, the so-called "deplating" cell, which is operated with a special electrolyte.
  • An electrolyte based on an aqueous sodium chloride solution has proven to be particularly advantageous.
  • other soluble metal chlorides e.g. Potassium chloride, magnesium chloride and the like can be used.
  • These hydroxides precipitated from the electrolyte are produced using known methods such as e.g. Settling and / or filtration and hydrocyclones or centrifugation removed from the solution.
  • FIG. 1 shows a schematic of a "deplating" cell constructed in this way.
  • the belt 10 at least runs through Electrode pair 11, 12 or 11 ', 12', a part of which is connected anodically and a part is connected cathodically.
  • the side of the strip opposite the anode 11, 11 ' is thereby cathodically polarized and the side opposite the cathode 12, 12' is anodically polarized and the alloy is detached from this side.
  • the current required to dissolve the coating is not the same as the current to the coating, but is approximately two to five times that.
  • the electrodes in the detachment cell it is also necessary that they are always completely covered with electrolyte and that the electrolyte level 13 in the cell is higher than the upper edge of the anode in order to avoid the formation of gaseous chlorine.
  • electrolyte level 13 in the cell is higher than the upper edge of the anode in order to avoid the formation of gaseous chlorine.
  • stainless steel and nickel or other known electrode materials can be used as the electrode material for the detachment cell, and platinum-coated or iridium oxide-coated titanium sheets can be used as the anode.
  • the temperature range for the electrolyte in the detachment cell is between 20 and 90 ° C, preferably between 40 and 65 ° C.
  • the belt coming from the detachment cell 5 passes through a further rinsing system 4 'and finally through a dryer 6.
  • a steel strip was coated on one side with a zinc-nickel alloy in an electrolytic coil coating system.
  • the uncoated side was discolored brown and chemical cementation of the nickel on the uncoated side could be detected in the scanning electron microscope.
  • the plant was thereupon expanded with a detachment cell according to the invention and electrolytically applied a protective layer in the first cell.
  • An aqueous sodium sulfate solution was used as the electrolyte, and the current was supplied for detachment by an anodically connected current roller. When setting a current that corresponded to the theoretical protective layer, this was only partially removed. Only when the current was increased to three times the band was free of the deposited layer, but the surface was discolored light brown after the rinsing process.
  • the surface was free of zinc-nickel residues only after three times the theoretical amount of electricity, but was slightly discolored in brown, and phosphate crystals could be partially detected on the surface using the scanning electron microscope.

Description

Die Erfindung betrifft ein Verfahren zur einseitigen elektrolytischen Beschichtung flächiger Werkstücke aus Stahl, insbesondere Stahlbander, mit einem Metall bzw. einer Metallegierung, insbesondere mit einer Zink-Nickel-Legierung, wobei nach Aufbringen einer dünnen Schicht aus demselben Material, das für die einseitige Beschichtung vorgesehen ist, auf beiden Seiten des Werkstückes die einseitige Beschichtung durchgeführt wird und schließlich eine elektrolytische Ablösung der dünnen Schicht auf der Seite, welche der dauerhaft zu beschichtenden Seite gegenüberliegt, erfolgt, wobei das Werkstück zur elektrolytischen Ablösung als Mittelleiter geschaltet wird.The invention relates to a method for the one-sided electrolytic coating of flat workpieces made of steel, in particular steel strip, with a metal or a metal alloy, in particular with a zinc-nickel alloy, whereby after applying a thin layer of the same material that is provided for the one-sided coating is, the one-sided coating is carried out on both sides of the workpiece and finally there is an electrolytic detachment of the thin layer on the side opposite the side to be permanently coated, the workpiece being switched as a central conductor for electrolytic detachment.

In den letzten Jahren sind verschiedene Verfahren zur elektrolytischen Beschichtung eines Stahlbandes mit einer Zink-Nickel-Legierung beschrieben worden, die sich aber alle auf die beidseitige Beschichtung beziehen. Will man jedoch die Beschichtung nur einseitig durchführen und transportiert dabei das Stahlband durch den Elektrolyt, der Zink und Nickelsalze enthält, so bekommt man auf der unbeschichteten Seite eine Zementation des Nickels auf dem Stahlblech, die in der anschließenden Weiterverarbeitung stört.Various processes for the electrolytic coating of a steel strip with a zinc-nickel alloy have been described in recent years, but all of them relate to the coating on both sides. However, if you only want to carry out the coating on one side and thereby transport the steel strip through the electrolyte, which contains zinc and nickel salts, you get a cementation of the nickel on the uncoated side on the steel sheet, which disrupts the subsequent further processing.

Die Aufgabe der Erfindung war es daher, ein Verfahren zu schaffen, welches den oben angeführten Nachteil der Zementation auf der unbeschichteten Seite vermeidet.The object of the invention was therefore to provide a method which avoids the above-mentioned disadvantage of cementation on the uncoated side.

Zur Lösung dieser Aufgabe wird ein Verfahren vorgeschlagen, das dadurch gekennzeichnet ist, daß als Elektrolyt bei der Ablösung eine wässrige Lösung eines Alkali- oder Erdalkalichlorids, vorzugsweise Natrium- oder Kaliumchlorid, bei einem pH-Wert von 7 bis 12 verwendet wird.To achieve this object, a method is proposed which is characterized in that an aqueous solution of an alkali metal or alkaline earth metal chloride, preferably sodium or potassium chloride, at a pH of 7 to 12 is used as the electrolyte in the detachment.

In der nachfolgenden Beschreibung soll die Erfindung und weitere Merkmale davon unter Bezugnahme auf die beigefügte Zeichnung näher erläutert werden.

  • Fig. 1 zeigt ein Schema einer Galvanikanlage zur Durchführung des erfindungsgemäßen Verfahrens, und
  • Fig. 2 den schematischen Aufbau der Ablösezelle.
In the following description, the invention and further features thereof will be explained in more detail with reference to the accompanying drawing.
  • 1 shows a diagram of an electroplating system for carrying out the method according to the invention, and
  • Fig. 2 shows the schematic structure of the detachment cell.

Das Stahlband wird nach Durchlaufen der Reinigungsanlage 1 in der ersten Zelle bzw. im Einlaufteil 2 in die Galvanikanlage 3 auf beiden Seiten mit einer Zink-Nickel-Legierung beschichtet, die in den weiteren Zellen die chemische Zementation des Nickels auf dieser Seite vermeiden soll.After passing through the cleaning system 1 in the first cell or in the inlet part 2 into the electroplating system 3, the steel strip is coated on both sides with a zinc-nickel alloy, which is to avoid chemical cementation of the nickel on this side in the other cells.

Erst danach erfolgt in einer weiteren Zelle, bzw. in einem anschließenden Teil 2' der Anlage 3 die einseitige Beschichtung mit herkömmlichen Einrichtungen (wie z.B. Stromrolle als Kontaktelement für das Band, etc.)Only then does the one-sided coating with conventional devices (such as a current roller as a contact element for the belt, etc.) take place in a further cell or in a subsequent part 2 'of the system 3.

Sobald diese Beschichtung abgeschlossen und das Band durch die Spülanlage 4 gelaufen ist, wird gemäß der Erfindung die zuerst aufgebrachte Beschichtung in einer weiteren Zelle 5, der sogenannten "Deplating"-Zelle, die mit einem speiziellen Elektrolyt betrieben wird, wieder abgelöst. Als besonders vorteilhaft hat sich dabei ein Elektrolyt auf Basis einer wässrigen Natriumchloridlösung herausgestellt. Es können aber selbstverständlich auch andere lösliche Metallchloride, wie z.B. Kaliumchlorid, Magnesiumchlorid und ähnliche verwendet werden. Als pH-Wert der Lösung hat sich als besonders günstig eine neutrale Lösung von pH = 7 bzw. leicht alkalische Lösung mit einem pH-Wert bis zu 12 herausgestellt, da in diesem pH-Bereich die gelösten Metalle Zink und Nickel sofort als Hydroxide ausfallen und keine weitere Zementation auf dem Stahlband verursachen können. Diese aus dem Elektrolyt ausgefallenen Hydroxide werden mit bekannten Methoden wie z.B. Absetzen und/oder Filtration sowie Hydrozyklone oder Zentrifugieren aus der Lösung entfernt.As soon as this coating has been completed and the belt has passed through the rinsing system 4, the coating applied first is detached again in a further cell 5, the so-called "deplating" cell, which is operated with a special electrolyte. An electrolyte based on an aqueous sodium chloride solution has proven to be particularly advantageous. Of course, other soluble metal chlorides, e.g. Potassium chloride, magnesium chloride and the like can be used. A neutral solution of pH = 7 or slightly alkaline solution with a pH up to 12 has proven to be particularly favorable as the pH of the solution, since in this pH range the dissolved metals zinc and nickel immediately precipitate out as hydroxides and can cause no further cementation on the steel belt. These hydroxides precipitated from the electrolyte are produced using known methods such as e.g. Settling and / or filtration and hydrocyclones or centrifugation removed from the solution.

Zum Auflösen der Zink-Nickel-Legierung muß das Band anodisch geschaltet werden. Versuche haben gezeigt, daß dafür eine Schaltung, die man in der Technik als Mittelleiter bezeichnet, von Vorteil ist. Die Fig. 2 zeigt ein Schema einer derartig aufgebauten "Deplating"-Zelle. Dabei durchläuft das Band 10 zumindest ein Elektrodenpaar 11, 12 bzw. 11', 12', von dem ein Teil anodisch und ein Teil kathodisch geschaltet ist. Die der Anode 11, 11' gegenüberstehende Seite des Bandes wird dadurch kathodisch polarisiert und die der Kathode 12, 12' gegenüberliegende Seite anodisch polarisiert und von dieser Seite wird die Legierung abgelöst.To dissolve the zinc-nickel alloy, the strip must be switched anodically. Experiments have shown that a circuit which is referred to in technology as a center conductor is advantageous. 2 shows a schematic of a "deplating" cell constructed in this way. The belt 10 at least runs through Electrode pair 11, 12 or 11 ', 12', a part of which is connected anodically and a part is connected cathodically. The side of the strip opposite the anode 11, 11 'is thereby cathodically polarized and the side opposite the cathode 12, 12' is anodically polarized and the alloy is detached from this side.

Überraschenderweise ist der Strom, der zum Auflösen der Beschichtung notwendig ist, nicht gleich dem Strom zur Beschichtung, sondern beträgt etwa das Zwei- bis Fünffache davon.Surprisingly, the current required to dissolve the coating is not the same as the current to the coating, but is approximately two to five times that.

Für die Anordnung der Elektroden in der Ablösezelle ist es weiters notwendig, daß diese stets komplett mit Elektrolyt bedeckt sind und daß der Elektrolytspiegel 13 in der Zelle höher als die Oberkante der Anode ist, um die Bildung von gasförmigem Chlor zu vermeiden. Als Elektrodenmaterial für die Ablösezelle können sowohl Edelstahl als auch Nickel oder andere bekannte Elektrodenmaterialien und als Anode auch platinierte bzw. mit Iridiumoxid beschichtete Titanbleche verwendet werden.For the arrangement of the electrodes in the detachment cell, it is also necessary that they are always completely covered with electrolyte and that the electrolyte level 13 in the cell is higher than the upper edge of the anode in order to avoid the formation of gaseous chlorine. Both stainless steel and nickel or other known electrode materials can be used as the electrode material for the detachment cell, and platinum-coated or iridium oxide-coated titanium sheets can be used as the anode.

Der Temperaturbereich für den Elektrolyten in der Ablösezelle liegt zwischen 20 und 90° C, vorzugsweise zwischen 40 und 65°C.The temperature range for the electrolyte in the detachment cell is between 20 and 90 ° C, preferably between 40 and 65 ° C.

Das aus der Ablösezelle 5 kommende Band durchläuft noch eine weitere Spülanlage 4' und schließlich einen Trockner 6.The belt coming from the detachment cell 5 passes through a further rinsing system 4 'and finally through a dryer 6.

Ausführungsbeispiele:Examples:

In einer elektrolytischen Bandbeschichtungsanlage wurde ein Stahlband einseitig mit einer Zink-Nickel-Legierung beschichtet. Beim Auslauf des Bandes war die unbeschichtete Seite braun verfärbt und im Rasterelektronenmikroskop konnte chemische Zementation des Nickels auf der unbeschichteten Seite nachgewiesen werden. Die Anlage wurde daraufhin mit einer Ablösezelle gemäß der Erfindung erweitert und in der ersten Zelle elektrolytisch eine Schutzschicht aufgebracht. Als Elektrolyt wurde eine wässrige Natriumsulfatlösung verwendet und die Stromzuführung zum Ablösen erfolgte durch eine anodisch geschaltete Stromrolle. Bei Einstellen eines Stroms, der der theoretischen Schutzschicht entsprach, war diese nur zum Teil entfernt. Erst bei Erhöhung des Stroms auf den dreifachen Wert war das Band frei von der abgeschiedenen Schicht, die Oberfläche war nach dem Spülvorgang jedoch hellbraun verfärbt. Der Elektrolyt wurde daraufhin gegen eine wässrige Natriumphosphatlösung, die auf pH = 7 eingestellt war, ausgetauscht. Auch hier war die Oberfläche erst nach der dreifachen theoretischen Strommenge frei von Zink-Nickel-Resten, doch leicht braun verfärbt und im Rasterelektronenmikroskop konnten teilweise auf der Oberfläche Phosphatkristalle nachgewiesen werden. Nur nach Verwendung eines Natriumchloridelektrolyts und nach Einbau von Elektroden, die es ermöglichten, das Band nach dem Mittelleiterverfahren zu behandeln, war die Oberfläche nach der Ablösezelle metallisch blank und selbst im Rasterelektronenmikroskop konnten keine Verunreinigungen wie Zink- und Nickelreste nachgewiesen werden.A steel strip was coated on one side with a zinc-nickel alloy in an electrolytic coil coating system. When the strip ran out, the uncoated side was discolored brown and chemical cementation of the nickel on the uncoated side could be detected in the scanning electron microscope. The plant was thereupon expanded with a detachment cell according to the invention and electrolytically applied a protective layer in the first cell. An aqueous sodium sulfate solution was used as the electrolyte, and the current was supplied for detachment by an anodically connected current roller. When setting a current that corresponded to the theoretical protective layer, this was only partially removed. Only when the current was increased to three times the band was free of the deposited layer, but the surface was discolored light brown after the rinsing process. The electrolyte was then exchanged for an aqueous sodium phosphate solution which was adjusted to pH = 7. Here too, the surface was free of zinc-nickel residues only after three times the theoretical amount of electricity, but was slightly discolored in brown, and phosphate crystals could be partially detected on the surface using the scanning electron microscope. Only after using a sodium chloride electrolyte and after installing electrodes, which made it possible to treat the tape using the middle conductor method, was the surface after the detachment cell shiny metallic and no contaminants such as zinc and nickel residues could be detected even under the scanning electron microscope.

Claims (2)

  1. A process for the one-sided electrolytic coating of flat workpieces made of steel, in particular steel strips, with a metal or metal alloy, in particular with a zinc-nickel alloy, the one-sided coating being carried out after a thin layer of the same material provided for the one-sided coating has been applied to both sides of the workpiece, and the thin layer subsequently being detached on the side opposite the side to be coated permanently, the workpiece being connected as a neutral conductor for the purpose of electrolytic detachment, characterised in that an aqueous solution of an alkali chloride or alkaline earth chloride, preferably sodium chloride or potassium chloride, with a pH value of 7 to 12 is used as an electrolyte for this detachment.
  2. A process according to Claim 1, characterised in that the temperature of the electrolyte in the detachment cell is between 20 and 90° C, preferably between 40 and 65° C.
EP90890216A 1989-07-24 1990-07-24 Process for one side electroplating of flat workpieces Expired - Lifetime EP0410955B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT1778/89 1989-07-24
AT1778/89A AT393513B (en) 1989-07-24 1989-07-24 METHOD FOR ONE-SIDED ELECTROLYTIC COATING OF FLAT WORKPIECE FROM STEEL

Publications (2)

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EP0410955A1 EP0410955A1 (en) 1991-01-30
EP0410955B1 true EP0410955B1 (en) 1994-02-02

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EP90890216A Expired - Lifetime EP0410955B1 (en) 1989-07-24 1990-07-24 Process for one side electroplating of flat workpieces

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EP (1) EP0410955B1 (en)
JP (1) JPH0361397A (en)
KR (1) KR910003156A (en)
AT (1) AT393513B (en)
BR (1) BR9003557A (en)
CA (1) CA2021654A1 (en)
DE (1) DE59004484D1 (en)
YU (1) YU47229B (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992021792A1 (en) * 1991-05-30 1992-12-10 Sikel N.V. Method and apparatus for continuously preparing a steel strip having an electrolytically deposited coating layer
EP1081252A1 (en) * 1999-09-02 2001-03-07 Enthone-OMI (Benelux) B.V. Selective plating method
EP1181993A1 (en) 2000-08-18 2002-02-27 Ti Group Automotive Systems Limited A method for manufacturing a multiple walled tube
US10526742B2 (en) * 2015-06-19 2020-01-07 Samsung Electronics Co., Ltd. Washing machine
CN111519221A (en) * 2020-04-15 2020-08-11 本钢板材股份有限公司 Processing method for single-side electrogalvanizing

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3959099A (en) * 1975-06-18 1976-05-25 Inland Steel Company Electrolytic method of producing one-side-only coated steel
IT1076494B (en) * 1975-10-15 1985-04-27 Nat Steel Corp PROCEDURE FOR THE PRODUCTION OF GALVANIZED SHEET
JPS58181889A (en) * 1982-04-17 1983-10-24 Nippon Steel Corp Preparation of single surface zinc electroplated steel plate
JPS5996292A (en) * 1982-11-25 1984-06-02 Sumitomo Metal Ind Ltd Production of steel sheet electroplated on one side
US4464232A (en) * 1982-11-25 1984-08-07 Sumitomo Metal Industries, Lt. Production of one-side electroplated steel sheet
JPS59116391A (en) * 1982-12-21 1984-07-05 Sumitomo Metal Ind Ltd Production of steel sheet electroplated on one side
DD217541A1 (en) * 1983-09-13 1985-01-16 Orsta Hydraulik Veb K ELECTROCHEMICAL DECENTRIFICATION AND NEUTRALIZATION OF INTERLOCKED WORKPIECES
DE3727246C1 (en) * 1987-08-15 1989-01-26 Rasselstein Ag Process for the galvanic coating of a steel strip with a coating metal, in particular zinc or a zinc-containing alloy

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DE59004484D1 (en) 1994-03-17
JPH0361397A (en) 1991-03-18
CA2021654A1 (en) 1991-01-25
BR9003557A (en) 1991-08-27
ATA177889A (en) 1991-04-15
AT393513B (en) 1991-11-11
YU47229B (en) 1995-01-31
EP0410955A1 (en) 1991-01-30
YU140790A (en) 1993-05-28
KR910003156A (en) 1991-02-27

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