EP3763850A1 - Anode et procédé de dépôt électrolytique d'une couche métallique sur un substrat métallique - Google Patents

Anode et procédé de dépôt électrolytique d'une couche métallique sur un substrat métallique Download PDF

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Publication number
EP3763850A1
EP3763850A1 EP19185454.6A EP19185454A EP3763850A1 EP 3763850 A1 EP3763850 A1 EP 3763850A1 EP 19185454 A EP19185454 A EP 19185454A EP 3763850 A1 EP3763850 A1 EP 3763850A1
Authority
EP
European Patent Office
Prior art keywords
anode
cathode
distance
strip
metal substrate
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.)
Withdrawn
Application number
EP19185454.6A
Other languages
German (de)
English (en)
Inventor
Jacques Hubert Olga Joseph Wijenberg
Gijsbertus Cornelis Van Haastrecht
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.)
Tata Steel Ijmuiden BV
Original Assignee
Tata Steel Ijmuiden BV
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Tata Steel Ijmuiden BV filed Critical Tata Steel Ijmuiden BV
Priority to EP19185454.6A priority Critical patent/EP3763850A1/fr
Publication of EP3763850A1 publication Critical patent/EP3763850A1/fr
Withdrawn legal-status Critical Current

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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
    • C25D7/0642—Anodes
    • 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
    • C25D7/0628—In vertical cells
    • 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
    • C25D7/0692—Regulating the thickness of the coating

Definitions

  • the invention relates to an anode for use in method for electrolytically depositing a metal layer onto a metal substrate and to a process for electrolytically depositing a metal layer onto a metal substrate using said anode.
  • Electrolytically depositing a metal layer onto a substrate, or electroplating is a process that uses an electric current to reduce dissolved metal cations in an electrolyte so that they form a thin coherent metal coating on an electrically conductive substrate.
  • a process for electroplating a tin layer onto a steel substrate is known from practice and is described in detail e.g. in the handbook "The Making, Shaping and Treating of Steel", 10th ed., pp. 1146-1153 , where a description of a typical commercial tinplating process called FERROSTAN is given which description is incorporated herein by reference.
  • the electrolyte is replenished with tin cations by anodically dissolving tin into the electrolyte.
  • tin is dissolved into the electrolyte from anode bars hanging in the electrolyte from an anode bar (see Figure 1 ).
  • the anode bars must be replaced regularly, and the anode bar positions have to be adjusted regularly along the anode bridge to ensure that the distance between the anode bar surface and the steel strip to be plated remains constant (See Figure 2 ).
  • anode bars When the anode bars are spent to an agreed minimum thickness, they are removed from the plating section and recycled in a remelting process for new cast anodes.
  • EP1699949 discloses such a DSSA.
  • the anode bars and the anode bridge onto which the anode bars are mounted were replaced by a DSSA, e.g. in the form of a titanium basket filled with tin pellets (See Figure 3 ).
  • the baskets are resistant to the plating conditions, and the pellets dissolve anodically into the electrolyte through openings (holes, gauze, etc.) in the basket where the pellets contact the electrolyte.
  • the high electrical resistance of the steel strip is enough to cause an appreciable voltage (IR) drop in the steel strip.
  • IR appreciable voltage
  • the current density will be higher at the top of the pass than at the bottom. This can be largely overcome by tilting the anode so that it is closer to the strip at the bottom than at the top. This is also schematically depicted in Figure 3 . By doing so, the current density is more uniform along the strip between the tilted anodes compared to using anodes that are not tilted.
  • Anode baskets can also be used in electroplating processes for depositing zinc, chromium, iron, copper, cobalt and nickel plating, as well as for depositing alloys thereof, such as brass.
  • the metal substrate to be plated acts as the cathode in a continuous plating line, and is provided in the form of a metal strip.
  • the invention is described for the situation where the strip (cathode) moves between the anode(s) in a substantially vertical direction. This is the most used configuration in continuous plating lines. However, the invention is also applicable for plating lines where the strip (cathode) moves between the anode(s) in a different reaction, e.g. horizontally.
  • the situation is schematically depicted in Figure 4 for a vertical (i.e. the most used) configuration.
  • the anode is a dimensionally stable anode (DSA): an anode that preserves its shape and voltage characteristics even under the most severe conditions prevailing in electrolysis.
  • DSA dimensionally stable anode
  • a DSA may be provided in one of two different types:
  • a suitable material for a DSSA that does not dissolve under most operating conditions is titanium.
  • Other known DSSA basket materials that may be suitable depending on the plating conditions and the electrolyte are zirconium, niobium, stainless steel, carbon steel and monel.
  • a suitable material for a DSA that does not dissolve under most operating conditions is titanium provided with a catalytic coating such as platinum or a mixed metal oxide for promoting the oxygen evolution reaction.
  • DSSA are like DSA in the sense that these also preserve their shape and voltage characteristics even under the most severe conditions prevailing in electrolysis, but additionally serve as receptacles for metal pellets which dissolve into the electrolyte and enter the solution as metal cations available to be deposited onto the metal strip.
  • Pellets in the sense of the invention intend to encompass metal pellets, chunks, lumps, particles, balls, and the like, which can be deposited into the DSSA, e.g. by means of an automated feeder system or otherwise.
  • the system becomes insensitive for the exact placement of the anode.
  • the offset value xo is as small as possible. The minimum value is limited because too small an offset value could result in the cathode touching the anode which would lead to short circuiting and damage to strip and installation.
  • the voltage between anode and cathode is also smaller.
  • the current density is also homogeneous at the cathode if the anode has the ideal shape according to the invention. Whether the anode is placed close to the strip or further away, the current density at the strip is the homogeneous along its length when it is between the anodes. Consequently, the ideal shape of the anode face facing the strip is given by eq. 2 because it ensures a constant current density along its length, and the system is insensitive for the distance between the strip and the anode.
  • the resistance of the system increases or decreases depending on the placement of the anode because the distance between the anode and the strip changes. Consequently, the voltage between the anode and the cathode will increase or decrease accordingly.
  • the distance between the cathode and the tilted straight anode is defined as x L (y).
  • the distance between the cathode and the surface facing the cathode of the ideal DS(S)A is defined as x A (y) (see Figure 4 ).
  • the inventors found that deviations from the ideal shape of the DS(S)A still result in an improvement compared to the tilted straight DS(S)A. Although the optimum result is obtained for c 0, the benefits of the invention are still obtained for values of c larger than 0. The smaller the value of c, the more the current density approaches the ideal situation of complete uniformity between the anode and the cathode. Consequently, the invention is embodied in a DS(S)A that is provided with a surface that, in use, faces the cathode (i.e.
  • the homogeneity of the current density at the cathode is ideal by providing the DS(S)A with a surface that, in use, faces the cathode (i.e. the strip to be plated) wherein the surface is curved such that, in use, the distance between the anode and the cathode, x, is given by x A (y).
  • a DS(S)A provides the best homogeneity of the current density at the anode, and the homogeneity is also not dependent on the distance between the anode and the cathode.
  • the distance does affect the voltage needed to execute the plating process, but not the homogeneity at the cathode.
  • the invention is also embodied in an electrolytic plating line comprising one or more DS(S)A's.
  • the principle of the DS(S)A according to the invention is such that straight tilted anodes (DS(S)A or conventional replaceable anodes) can be easily replaced by the DS(S)A's according to the invention.
  • the dimensions are comparable to the conventional tilted anodes.
  • the use of the anodes according to the invention will result in the line providing a more homogeneous current density during the plating.
  • the anode or anodes according to the invention are used in a continuous plating line operating at a line speed of at least 10 m/min.
  • the benefit of these anodes is also useful in continuous high speed plating line operating at much higher line speeds of between 50 and 750 m/min.
  • the line speed is at least 75 m/min, more preferably at least 100 m/min, even more preferably at least 150 m/min.
  • Each line segment becomes either an insulator or an electrode as defined by the user.
  • the cell geometry is shown in Figure 6 .
  • line segment 3 is the anode and line segment 5 is the cathode (i.e. the strip).
  • the voltage drop over an electrode is calculated by assigning a value for the resistivity and the thickness of the electrode and the contact point of the electrode, which is either the 'Begin' or the 'End' of the line segment.
  • the line segments are divided into a number of elements and the local current density is calculated for each element. In order to obtain a unique numerical solution, at least one electrode should receive an imposed potential.
  • FIG. 1 A typical soluble anode system for a tinplating line is illustrated in Figure 1 .
  • tin is supplied by tin anode 1 which has an anode gap 2 and an anode notch 3.
  • Each of a series of tin anodes 1 is supported by an anode bridge 4 at a top portion near its anode notch 3 and at a bottom portion in anode box 5.
  • Isolated plate 6 separates two tinning sections in one plating cell. Electrical power is supplied to the strip via conductor roll 7. Near the bottom of the plating cell the strip is guided by sink roll 8. Hold-down roll 9 is also shown.
  • Anode bridge 4 comprises an insulated parking space 1 0 for a fresh tin anode 1.
  • the tin anodes 1 are connected to the anode bridge 4 via contact strip 14.
  • the thickness of the worn anodes is regularly checked with a thickness gauge.
  • the anode thickness becomes too small, the anode is detached from the anode bridge and placed on the nearest insulated parking space, see Figure 2 where the arrows indicate how the anodes "move" along the anode bridge.
  • a new anode is placed on the insulated parking space and transferred to the anode bridge. After each replacement, anodes need to be repositioned again.
  • a fresh tin anode is designated with N and a worn one with W.
  • FIG 3 shows, instead of individual tin bars, anode baskets 12 mounted on the anode bar 4 via contact strip 14.
  • the contact strips 14, made of copper in the experiments according to this example, may be coated on their surface contacting the anode basket 12 with a noble metal like Au or Pt.
  • the anode baskets 12 in Figure 6 were filled with tin pellets and, to replenish anodic substance, tin pellets are supplied regularly, which can be done while the plating line is fully operational.
  • the anode baskets 12 can be made of titanium and are designed and positioned.
  • Figure 5a shows a schematic drawing of a strip moving downwardly as a cathode in a plating cell with a straight tilted anode shown on one side, which is distanced from the cathode at a distance b at the top and at a distance a at the bottom of the anode.
  • the distance between the top and the bottom of the anode as seen by the cathode is h.
  • the distance from the anode to the cathode between the top and the bottom of the anode is given by x L .
  • the value of x L is b at the top and xo at the bottom of the anode.
  • Figure 5b shows a schematic drawing of a strip moving downwardly as a cathode in a plating cell with an anode according to the invention shown on one side, which is distanced from the cathode at a distance b at the top and at a distance xo at the bottom of the anode.
  • the distance between the top and the bottom of the anode as seen by the cathode is h.
  • the distance from the anode to the cathode between the top and the bottom of the anode is given by x A .
  • Figure 5c and 5d schematically show that it is also possible to use anodes wherein the surface facing the cathode is described is only a section (as indicated by the dashed box) of the complete surface as described in figure 5b .
  • Figure 6 shows the definition of the system for the BEM calculations.
  • Figure 7 shows the value of x(y) for the linear tilted anode (dashed line) and the anode according to the invention (ideal), as well as for three variations on the ideal line.
  • the line indicated with the triangle described by the line x x A (y)-0.5 ⁇ (x L (y)-x A (y));
  • Figure 8 shows the results of the calculations of the current density divided by the average current density. If the value is 1, then the current density is equal to the average current density.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating Methods And Accessories (AREA)
EP19185454.6A 2019-07-10 2019-07-10 Anode et procédé de dépôt électrolytique d'une couche métallique sur un substrat métallique Withdrawn EP3763850A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP19185454.6A EP3763850A1 (fr) 2019-07-10 2019-07-10 Anode et procédé de dépôt électrolytique d'une couche métallique sur un substrat métallique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19185454.6A EP3763850A1 (fr) 2019-07-10 2019-07-10 Anode et procédé de dépôt électrolytique d'une couche métallique sur un substrat métallique

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EP3763850A1 true EP3763850A1 (fr) 2021-01-13

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62188799A (ja) * 1986-02-14 1987-08-18 Nippon Kokan Kk <Nkk> 電気鍍金用電極
JPS62205299A (ja) * 1986-03-04 1987-09-09 Nippon Kokan Kk <Nkk> 電気鍍金用電極の電流密度調整方法
EP1699949A2 (fr) 2003-12-23 2006-09-13 Corus Staal BV Galvanoplastie perfectionnee sur bandes metalliques

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62188799A (ja) * 1986-02-14 1987-08-18 Nippon Kokan Kk <Nkk> 電気鍍金用電極
JPS62205299A (ja) * 1986-03-04 1987-09-09 Nippon Kokan Kk <Nkk> 電気鍍金用電極の電流密度調整方法
EP1699949A2 (fr) 2003-12-23 2006-09-13 Corus Staal BV Galvanoplastie perfectionnee sur bandes metalliques

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"The Making, Shaping and Treating of Steel", pages: 1146 - 1153

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