EP3733932A1 - Procédé de fabrication d'une bande métallique revêtue d'un revêtement de chrome et d'oxyde de chrome à base d'une solution électrolytique avec un composé à base de chrome trivalent et système d'électrolyse permettant la mise en oeuvre dudit procédé - Google Patents

Procédé de fabrication d'une bande métallique revêtue d'un revêtement de chrome et d'oxyde de chrome à base d'une solution électrolytique avec un composé à base de chrome trivalent et système d'électrolyse permettant la mise en oeuvre dudit procédé Download PDF

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Publication number
EP3733932A1
EP3733932A1 EP20156814.4A EP20156814A EP3733932A1 EP 3733932 A1 EP3733932 A1 EP 3733932A1 EP 20156814 A EP20156814 A EP 20156814A EP 3733932 A1 EP3733932 A1 EP 3733932A1
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EP
European Patent Office
Prior art keywords
electrolyte solution
chromium
electrolysis
coating
metal strip
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.)
Pending
Application number
EP20156814.4A
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German (de)
English (en)
Inventor
Andrea Dr. Marmann
Christoph Molls
Sebastian Hartung
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.)
ThyssenKrupp Rasselstein GmbH
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ThyssenKrupp Rasselstein GmbH
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Publication date
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Publication of EP3733932A1 publication Critical patent/EP3733932A1/fr
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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
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/04—Electroplating: Baths therefor from solutions of chromium
    • C25D3/06—Electroplating: Baths therefor from solutions of chromium from solutions of trivalent chromium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D9/00—Electrolytic coating other than with metals
    • C25D9/04—Electrolytic coating other than with metals with inorganic materials
    • C25D9/08—Electrolytic coating other than with metals with inorganic materials by cathodic processes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
    • C25D17/02—Tanks; Installations therefor
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
    • C25D17/10—Electrodes, e.g. composition, counter electrode
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
    • C25D17/16—Apparatus for electrolytic coating of small objects in bulk
    • C25D17/28—Apparatus for electrolytic coating of small objects in bulk with means for moving the objects individually through the apparatus during treatment
    • 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
    • C25D5/34—Pretreatment of metallic surfaces to be electroplated
    • C25D5/36—Pretreatment of metallic surfaces to be electroplated of iron or steel
    • 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
    • C25D5/48—After-treatment of electroplated surfaces
    • 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
    • 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
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/06—Wires; Strips; Foils
    • C25D7/0614—Strips or foils
    • C25D7/0621—In horizontal 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
    • C25D7/0642—Anodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D9/00—Electrolytic coating other than with metals
    • C25D9/04—Electrolytic coating other than with metals with inorganic materials
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D9/00—Electrolytic coating other than with metals
    • C25D9/04—Electrolytic coating other than with metals with inorganic materials
    • C25D9/08—Electrolytic coating other than with metals with inorganic materials by cathodic processes
    • C25D9/10—Electrolytic coating other than with metals with inorganic materials by cathodic processes on iron or steel

Definitions

  • the invention relates to a method for producing a metal strip coated with a coating according to the preamble of claim 1, as well as an electrolysis system for the electrolytic deposition of a coating containing chromium and chromium oxide on the surface of a metal strip.
  • tin-free steel sheet steel sheets which are electrolytically coated with a coating of chromium and chromium oxide are known from the prior art, which are referred to as tin-free steel sheet ("Tin Free Steel", TFS) or as “Electrolytic Chromium Coated Steel (ECCS)" and a Represent an alternative to tinplate.
  • TFS Tin Free Steel
  • ECCS Electrolytic Chromium Coated Steel
  • tin-free steel sheets are particularly characterized by good adhesion for paints or organic protective coatings (such as, for example, polymer coatings made of PP or PET).
  • these chromium-coated steel sheets have good corrosion resistance and good processability in forming processes for the production of packaging, e.g. in deep-drawing and ironing processes.
  • electrolytic coating processes are known from the prior art, with which the coating is applied in a strip coating system to a strip-shaped steel sheet using an electrolyte containing chromium VI.
  • these coating processes have considerable disadvantages and will have to be replaced by alternative coating processes in the foreseeable future, as the use of chromium VI-containing materials will be prohibited in the future.
  • Organic substances in particular formates and preferably sodium or potassium formate, are used as complexing agents.
  • the electrolyte solution can contain sulfuric acid.
  • the coating of chromium metal and chromium oxide can be deposited in layers in successive electrolysis tanks or strip coating systems arranged one after the other, the electrolysis tanks each being filled with the same electrolyte solution.
  • the electrodeposited coating can also contain chromium sulfates and chromium carbides in addition to the components chromium metal and chromium oxide and that the proportion of these components in the total weight of the coating depends to a large extent on the current densities set in the electrolysis tanks.
  • the coating contains a higher one Proportion of chromium oxide, which makes up between 1 ⁇ 4 and 1/3 of the total weight of the coating in the area of higher current densities.
  • the values of the current density thresholds, which the areas (Regime I to III) are dependent on the belt speed with which the steel sheet is moved through the electrolyte solution.
  • the object of the present invention is to provide a method that is as efficient, cost-effective and energy-saving as possible for producing a metal strip with a coating containing chromium oxide and based on an electrolyte solution with a trivalent chromium compound.
  • the use of chromium VI-containing substances, including as intermediate products of the electrolysis process, should be avoided in order to be able to fully comply with the legal requirements regarding the ban on chromium VI-containing substances.
  • the metal strip coated according to the method should have the highest possible corrosion resistance and a good adhesive base for organic coatings, e.g. for organic paints and for polymer coatings, in particular for polymer films, e.g. made of PET, PE or PP.
  • a coating which contains chromium metal and chromium oxide / chromium hydroxide is electrolytically produced from an electrolyte solution which contains a trivalent chromium compound and at least one salt to increase conductivity and at least one acid or base to set a desired pH , applied to a metal strip, in particular a steel strip, in that the metal strip is brought into contact with the electrolyte solution in an electrolytically effective manner, the metal strip being guided successively at a predetermined strip speed in a strip running direction through several electrolysis tanks arranged one behind the other in the strip running direction, at least the one in the strip running direction seen first electrolysis tank or a front group of electrolysis tanks is filled with a first electrolyte solution and the last electrolysis tank or a rear group of electrolysis tanks with a second electrolyte solution when viewed in the direction of belt travel is filled, wherein the second electrolyte solution, apart from a trivalent chromium compound and at least one salt and at least one
  • a second electrolyte solution which does not contain any organic complexing agents, is contained in the last electrolysis tank seen in the strip running direction or in the rear group of electrolysis tanks.
  • a layer consisting at least essentially of pure chromium oxide and / or chromium hydroxide can be produced on the surface of the coating.
  • the underlying layers of the coating contained in the or The electrolysis tank (s) upstream in the direction of travel of the strip contain not only a chromium oxide / chromium hydroxide component but also a proportion of metallic chromium, because the upstream electrolysis tank contains a first electrolyte solution, the (organic) complexing agents, in particular formates such as sodium or potassium formate , contains.
  • the coating applied electrolytically to the surface of the metal strip is thus composed of several superimposed layers, the lower layer (s) containing or containing a mixture of chromium metal and chromium oxide and / or chromium hydroxide, and possibly other chromium compounds such as chromium carbides.
  • the top layer, which forms the surface of the coating consists at least essentially of pure chromium oxide and / or chromium hydroxide.
  • the weight of the individual layers can be controlled in particular by the electrolysis times in the individual electrolysis tanks and set to desired values.
  • chromium oxide When chromium oxide is spoken of, all oxide forms of chromium (CrOx), including chromium hydroxides, in particular chromium (III) hydroxide and chromium (III) oxide hydrate, as well as mixtures thereof are meant.
  • the coating thus contains (in addition to metallic chromium) preferably exclusively trivalent chromium compounds and in particular only trivalent chromium oxides and / or chromium hydroxides.
  • the top layer of the coating which is applied in the last electrolysis tank or in the rear group of electrolysis tanks, preferably has a proportion by weight of chromium oxides, including chromium hydroxides, of more than 90%, particularly preferably more than 95%. This ensures a good adhesive base with good adhesion for organic coatings such as paints or polymer layers made of thermoplastics such as PET or PP.
  • the metal strip which can be, for example, a (initially uncoated) steel strip (black plate strip) or a tin-plated steel strip (tinplate strip), is placed in the first electrolysis tank or in the front group of electrolysis tanks during a first Electrolysis time t1 in contact with the first electrolyte solution and then in the second electrolysis tank or in the rear group of electrolysis tanks during a second electrolysis time t2 in contact with the second electrolyte solution brought.
  • the metal strip is guided successively through the electrolysis tanks arranged one behind the other in the strip running direction, the strip speed being at least 100 m / min and preferably between 200 m / min and 750 m / min. Due to the high belt speeds, a high efficiency of the process can be guaranteed.
  • the first electrolysis period in which the metal belt is in effective electrolytic contact with the first electrolyte solution is less than 2.0 seconds and the second electrolysis period in which the metal belt is in effective electrolytic contact with the second electrolyte solution is also preferably less than 2.0 seconds.
  • the electrolysis times in the last electrolysis tank or the rear group of electrolysis tanks are expediently set via the belt speed so that the layer of chromium oxide applied from the second electrolyte solution has a total weight of the chromium oxide of at least 3 mg / m 2 and preferably 7 mg / m 2 to 10 mg / m 2 .
  • These chromium oxide weights ensure adequate corrosion resistance and provide a good adhesive base for organic coatings such as paints or thermoplastic films.
  • a weight of the chromium oxide in the top layer of at least 5 mg / m 2 , preferably more than 7 mg / m 2 , is preferred.
  • a layer made of an organic material in particular a lacquer or a thermoplastic plastic, in particular a polymer film made of PET, PE, PP or a mixture thereof, can be applied to the surface of the coating (i.e. to the upper layer made of chromium oxide / chromium hydroxide).
  • a suitable anode is expediently selected for the electrolytic deposition of the coating and placed in the electrolysis tanks, which oxidizes chromium (III) from the trivalent chromium compound of the electrolyte solution to chromium ( VI) prevents.
  • anodes with an outer surface or a coating made of a metal oxide, in particular iridium oxide, or of a mixed metal oxide, in particular of iridium-tantalum oxide, have proven to be suitable for this.
  • the anode preferably contains neither stainless steel nor platinum.
  • the measurement in the associated Daniell element serves as the basis for the potentials.
  • the potential of the redox equation depends on the anode material used. The choice of the anode material therefore largely determines whether reaction (1) is suppressed and only reaction (2) takes place.
  • anodes based on metal oxides, especially iridium oxide, or mixed metal oxides, such as mixed metal oxides, which mainly consist of multilayered layers of tantalum oxide and iridium oxide can be used to suppress reaction 1 consist.
  • the anodes can have an outer surface or an outer coating made of a mixed metal oxide.
  • anodes with a core made of titanium and an outer coating made of a tantalum oxide-iridium oxide have proven to be suitable.
  • polarographic measurements showed that no Cr (VI) was produced.
  • chromium oxide Since already in the first electrolysis tank or in the front group of electrolysis tanks and possibly in a middle electrolysis tank or in a middle group of electrolysis tanks a certain weight proportion of the total application of the deposited coating, which is typically around 9 to 25%, is on the chromium oxide , including chromium hydroxide is omitted, chromium oxide crystals are already formed on the surface of the metal strip in the first electrolysis tank or in the front group of electrolysis tanks and in the middle electrolysis tank or in the middle group of electrolysis tanks.
  • chromium oxide crystals act in the last electrolysis tank and / or in the rear group of electrolysis tanks as a nucleus for the growth of further oxide crystals, which is why the efficiency of the deposition of chromium oxide or the proportion of chromium oxide in the total application of the coating in the last electrolysis tank or in the rear Group of electrolysis tanks is improved.
  • a sufficiently high weight of chromium oxide, including chromium hydroxide, of preferably more than 5 mg / m 2 can be produced on the surface of the coating in an efficient manner.
  • the belt speed of the metal belt is preferably chosen so that the electrolysis time (t E ), in which the metal belt is in effective electrolytic contact with the electrolyte solution, is less than 2.0 seconds in each of the electrolysis tanks and in particular between 0.5 and 1, 9 seconds and is preferably less than 1.0 seconds and in particular between 0.6 seconds and 0.9 seconds.
  • t E the electrolysis time
  • the belt speed of the metal belt is preferably chosen so that the electrolysis time (t E ), in which the metal belt is in effective electrolytic contact with the electrolyte solution, is less than 2.0 seconds in each of the electrolysis tanks and in particular between 0.5 and 1, 9 seconds and is preferably less than 1.0 seconds and in particular between 0.6 seconds and 0.9 seconds.
  • the proportion by weight of chromium oxide contained in the coating in relation to the total weight of the coating is preferably more than 10%, particularly preferably more than 20% and in particular between 25 and 50%.
  • the total electrolysis time (t E ) in which the metal strip is in electrolytically effective contact with the electrolyte solution (E) is - added up over all electrolysis tanks - preferably less than 16 seconds and is in particular between 3 and 16 seconds.
  • the total electrolysis time is particularly preferably less than 8 seconds and is in particular between 4 seconds and 7 seconds.
  • the coating is deposited in layers, whereby in each of the electrolysis tanks, depending on the selected current density in the respective electrolysis tank and depending on the composition of the electrolyte solution, a layer with a different composition, in particular with a different chromium oxide content in the respective layer is generated.
  • a layer containing chromium metal and chromium oxide / chromium hydroxide with a proportion by weight of chromium oxide, including chromium hydroxide, of less than 15%, in particular from 6 to 10%, on the surface of the metal strip are deposited and in the last electrolysis tank or in the rear group of electrolysis tanks a layer which consists at least essentially of pure chromium oxide and / or chromium hydroxide.
  • the first and second electrolyte solutions each preferably have a temperature in the range from 20 ° C to 65 ° C and preferably in the range from 30 ° C to 55 ° C and particularly preferably between 35 ° C and 45 ° C. At these temperatures the electrolytic deposition of the layers is very efficient.
  • the temperature of the electrolyte solution or the temperature in an electrolysis tank is spoken of, what is meant is the mean temperature which is averaged over the entire volume of an electrolysis tank. As a rule, there is a temperature gradient in the electrolysis tanks with a temperature increase from top to bottom.
  • Both the first electrolyte solution and the second electrolyte solution preferably contain, in addition to the trivalent chromium compound, at least one salt which increases the conductivity and at least one acid or base for setting a suitable pH value.
  • Both the first electrolyte solution and the second electrolyte solution are preferably free from chloride ions and free from buffering agents, in particular free from a boric acid buffer.
  • the trivalent chromium compound of the first electrolyte solution and / or the second electrolyte solution is preferably selected from the group consisting of basic Cr (III) sulfate (Cr 2 (SO 4 ) 3 ), Cr (III) nitrate (Cr (NO 3 ) 3 ), Cr (III) oxalate (CrC 2 O 4 ), Cr (III) acetate (C 12 H 36 ClCr 3 O 22 ), Cr (III) formate (Cr (OOCH) 3 ) or a mixture thereof .
  • the concentration of the trivalent chromium compound in the first electrolyte solution and / or in the second electrolyte solution is preferably at least 10 g / l and particularly preferably more than 15 g / l and in particular 20 g / l or more.
  • both the first electrolyte solution and the second electrolyte solution contain at least one salt, which is preferably an alkali metal sulfate, in particular potassium or sodium sulfate.
  • a very efficient deposition of a chromium and / or chromium oxide-containing layer is achieved if the pH (measured at a temperature of 20 ° C.) of the first electrolyte solution and / or the second electrolyte solution is in a range from 2.3 to 5.0 and is preferably between 2.5 and 2.9.
  • the desired pH can be adjusted by adding an acid or base to the first or second electrolyte solution. If basic Cr (III) sulfate is used as the trivalent chromium compound, sulfuric acid or an acid mixture containing sulfuric acid is particularly suitable for setting the desired pH.
  • composition of the first electrolyte solution and the second electrolyte solution differs in that the first electrolyte solution contains organic complexing agents, in particular in the form of formates, preferably in the form of potassium or sodium formate, whereas the second electrolyte solution is preferably free of complexing agents and in particular no organic Contains complexing agents such as formates.
  • compositions of the first and the second electrolyte solution each comprise basic Cr (III) sulfate (Cr 2 (SO 4 ) 3 ) as a trivalent chromium compound.
  • concentration of the trivalent chromium compound in the first and the second electrolyte solution is at least 10 g / l and preferably more than 15 g / l and is in particular 20 g / l or more.
  • Further components of the first electrolyte solution are a salt to increase conductivity, as well as organic complexing agents, in particular the salts of formic acid, such as potassium format or sodium format.
  • the ratio of the proportion by weight of the trivalent chromium compound to the proportion by weight of the complexing agents, in particular the formates, is preferably between 1: 1.1 and 1: 1.4 and preferably between 1: 1.2 and 1: 1.3 and in particular 1: 1.25.
  • the second electrolyte solution preferably contains no further components. This ensures a simple and inexpensive production of the second electrolyte solution.
  • the trivalent chromium compound which has initially been largely freed from organic residues, as well as the at least one salt and the at least one acid or base can be dissolved in water to set a desired pH. Since the second electrolyte solution does not contain any complexing agents, the solution thus obtained should expediently be left to stand for complex formation for at least 5 days, preferably 7 days (in atmospheric oxygen). Thereafter, no fine adjustment of the desired pH value can be made by adding an acid or base.
  • metal strips in particular steel strips, can be produced with an electrolytically deposited coating which contains chromium and chromium oxide / chromium hydroxide, the coating being composed of a first layer facing the surface of the metal strip and a second layer lying thereon and the first layer being metallic Contains chromium and the second layer consists at least essentially only of chromium oxide and / or chromium hydroxide, preferably only of trivalent chromium oxides and / or chromium hydroxides and preferably has a proportion by weight of chromium oxide and / or chromium hydroxide of more than 90%, particularly preferably of more than 95%.
  • Such metal strips according to the invention are distinguished by a high level of corrosion resistance and good adhesion for organic coatings such as paints or polymer layers.
  • the coating preferably contains at least essentially only compounds of chromium and oxygen in which the chromium is in trivalent form, in particular as Cr 2 O 3 and / or Cr (OH) 3, apart from unavoidable impurities.
  • FIG. 1 a coil coating system for performing the method according to the invention is shown schematically in a first embodiment.
  • the coil coating system comprises three electrolysis tanks 1a, 1b, 1c arranged next to one another or one behind the other, each of which is filled with an electrolyte solution E.
  • an initially uncoated metal strip M for example a black plate or tin plate strip
  • the metal strip M is pulled through the electrolysis tanks 1a-1c in a strip running direction v at a predetermined strip speed by a transport device (not shown here).
  • power rollers S are arranged, via which the metal strip M is connected as a cathode.
  • a deflection roller U is also arranged, around which the metal strip M is guided and is thereby directed into and out of the electrolysis tank.
  • each electrolysis tank 1a-1c at least one pair of anodes AP is arranged below the liquid level of the electrolyte solution E.
  • two pairs of anodes AP arranged one behind the other in the direction of travel of the strip are provided in each electrolysis tank 1a-1c.
  • the metal strip M is passed between the opposing anodes of an anode pair AP.
  • two pairs of anodes AP are arranged in each electrolysis tank 1a, 1b, 1c in such a way that the metal strip M is passed through these anode pairs AP one after the other.
  • the last anode pair APc in the downstream direction of the last electrolysis tank 1c seen in the strip running direction v has a shortened length compared to the other anode pairs AP. As a result, a higher current density can be generated with this last pair of anodes APc when an electric current of the same level is applied.
  • the metal strip M can be an initially uncoated steel strip (black plate strip) or also a tinned steel strip (tin plate strip).
  • the metal strip M is first degreased, rinsed, pickled and rinsed again and, in this pretreated form, passed one after the other through the electrolysis tanks 1a-1c, the metal strip M being connected as a cathode by supplying electrical current via the current rollers S.
  • the belt speed at which the metal belt M is passed through the electrolysis tanks 1a-1c is at least 100 m / min and can be up to 900 m / min.
  • the front electrolysis tanks 1a and 1b seen in the strip running direction v are each filled with the same electrolyte solution E1.
  • This first electrolyte solution E1 contains a trivalent chromium compound, preferably basic Cr (III) sulfate, Cr 2 (SO 4 ) 3 .
  • the first electrolyte solution E1 contains at least one organic complexing agent, for example a salt of formic acid, in particular potassium or sodium format.
  • the ratio of the proportion by weight of the trivalent chromium compound to the proportion by weight of the complexing agents, in particular the formates, is preferably between 1: 1.1 and 1: 1.4 and particularly preferably 1: 1.25.
  • the first electrolyte solution E1 contains a salt, in particular. an alkali metal sulfate, for example potassium or sodium sulfate.
  • concentration of the trivalent chromium compound in the first electrolyte solution E1 is at least 10 g / l and particularly preferably 20 g / l or more.
  • the temperature of the first electrolyte solution E1 is expediently the same in the two front electrolysis tanks 1a, 1b and is preferably between 25.degree. C. and 70.degree. However, different temperatures of the electrolyte solution can also be set in the two front electrolysis tanks 1a-1b. For example, the temperature of the electrolyte solution in the middle electrolysis tank 1b can be lower than in the front electrolysis tank 1a arranged upstream.
  • the temperature of the electrolyte solution in the middle electrolysis tank 1b is preferably between 25 ° C and 37 ° C and in particular 35 ° C and the temperature of the first electrolyte solution E1 in the front electrolysis tank 1a is preferably between 40 ° C and 75 ° C and in particular at 55 ° C.
  • the rear or last electrolysis tank 1c seen in the strip running direction v is filled with a second electrolyte solution E2, the composition of which differs from the first electrolyte solution E1 at least in that the second electrolyte solution E2 contains no organic constituents and in particular no complexing agents. Otherwise, the constituent parts of the second electrolyte solution E2 can correspond to the first electrolyte solution E1.
  • the second electrolyte solution E2 also contains a trivalent chromium compound, preferably basic Cr (III) sulfate, Cr 2 (SO 4 ) 3, and at least one salt and one acid or base for setting a suitable pH value.
  • the salt which, like the first electrolyte solution E1, is an alkali metal sulfate, for example Potassium or sodium sulfate, serves to increase the conductivity.
  • the concentration of the trivalent chromium compound in the second electrolyte solution E2 is at least 10 g / l and particularly preferably 20 g / l or more.
  • the temperature of the second electrolyte solution E2 in the rear electrolysis tank 1c is expediently between 25 ° C and 70 ° C and is preferably between 25 ° C and 40 ° C, and is in particular 35 ° C.
  • the anode pairs AP arranged in the electrolysis tanks 1a-1c are supplied with electrical direct current in such a way that the electrolysis tanks 1a, 1b, 1c each have a sufficiently high current density to allow electrolytic deposition of a chromium-containing (in particular a Cr-III-containing) layer produce.
  • the minimum current density required for this depends on the belt speed and is, for example, at a (minimum) belt speed of 100 m / min approx. 15 to 20 A / dm 2 .
  • the minimum current density required for electrolytic deposition of a chromium-containing layer increases with higher belt speed.
  • the metal belt M connected as a cathode and passed through the electrolysis tanks 1a-1c is in electrolytically effective contact with the first electrolyte solution E1 during an electrolysis period t1 in the two front electrolysis tanks 1a, 1b and subsequently during an electrolysis period t2 in the rear electrolysis tank 1c in electrolytically effective contact with the second electrolyte solution E2.
  • the electrolysis time in each of the electrolysis tanks 1a, 1b, 1c is between 0.5 and 2.0 seconds.
  • Belt speeds are preferably set so high that the electrolysis time in each electrolysis tank 1a, 1b, 1c is less than 2 seconds and in particular is between 0.6 seconds and 1.8 seconds.
  • the total electrolysis time tG t1 + t2, in which the metal strip M is in electrolytically effective contact with the first and second electrolyte solutions E1, E2 across all electrolysis tanks 1a-1c, is accordingly between 1.8 and 5.4 seconds.
  • the duration of the electrolysis in the individual electrolysis tanks 1a, 1b, 1c can be adjusted on the one hand by the belt speed and on the other hand by the dimensioning of the electrolysis tanks 1a-1c.
  • a layer is deposited on at least one side of the metal strip M in the front electrolysis tank 1a and in the middle electrolysis tank 1b, which layer contains chromium and chromium oxide / Chromium hydroxide and chromium carbides and, if a sulfate-containing first electrolyte solution E1 is used, may contain chromium sulfates.
  • a layer B1 or B2 is produced in each of the two electrolysis tanks 1a, 1b, the composition of the layers B1, B2, in particular with regard to the proportion of chromium oxide / chromium hydroxide, being able to differ if in the front electrolysis tank 1a and the middle electrolysis tank 1b different electrolysis parameters, especially. Different current densities and temperatures, are used.
  • an upper layer B3 is deposited on at least one side of the metal strip M, which layer consists at least essentially of pure chromium oxide and / or chromium hydroxide.
  • the proportion by weight of the chromium oxide / chromium hydroxide in the total weight of the upper layer B3 is expediently at least 90%, preferably more than 95%.
  • FIG 3 a schematic sectional view of a metal strip M electrolytically coated using the method according to the invention is shown.
  • a coating B is applied to one side of the metal strip M, which is composed of the individual layers B1, B2, B3.
  • Each individual layer B1, B2, B3 is applied to the surface in one of the electrolysis tanks 1a, 1b, 1c.
  • the two lower layers B1, B2 facing the surface of the metal strip M contain metallic chromium (chromium metal) and chromium oxides (CrOx) / chromium hydroxides as well as chromium carbides and possibly chromium sulfates as essential components, the composition of the individual layers B1, B2 in particular with regard to their respective weight percentages of chromium metal and chromium oxide / chromium hydroxide can be the same or different, depending on whether the same or different electrolysis parameters have been used in the two front electrolysis tanks 1a, 1b.
  • the upper layer B2 facing away from the surface of the metal strip M essentially contains only chromium oxides (CrOx) and / or chromium hydroxides and in particular no chromium carbides and hardly any metallic chromium and hardly any chromium sulfates.
  • the layer structure of the layers B1, B2, B3 deposited on the metal substrate can be demonstrated by GDOES spectra ( Glow Discharge Optical Emission Spectroscopy ).
  • a metallic chrome layer with a thickness of 10-15 nm is first deposited on the metal strip M in the two front electrolysis tanks 1a, 1b.
  • the surface of this layer oxidizes and is mainly in the form of chromium oxide in the form of Cr 2 O 3 or as a mixed oxide hydroxide in the form of Cr 2 O 2 (OH) 2 .
  • This oxide layer is a few nanometers thick.
  • chromium-carbon and chromium sulfate compounds which are formed from the reduction of the organic complexing agent or the sulfate of the electrolyte solution, are formed evenly throughout the entire layer.
  • Typical GDOES spectra of the layers B1, B2 deposited in the individual electrolysis tanks show a strong increase in the oxygen signal in the first nanometers of the layer, from which it can be concluded that the oxide layer is concentrated on the surface of the respective layer ( Figure 4 ).
  • composition of the layers can be determined according to the EURO standard DIN EN 10202 (Cr-oxides photometric: (euro-norm) step 1: 40 ml NaOH (330g / L), reaction at 90 ° C for 10 minutes, oxidation with 10 ml 6 % H 2 O 2 , photometric @ 370 nm).
  • the metal strip M provided with the coating B is rinsed, dried and oiled (for example with DOS).
  • the metal strip M electrolytically coated with the coating B can then be provided with an organic coating.
  • the organic layer is applied in a known manner, for example by painting or laminating a plastic film onto the surface of the coating B, that is to say onto the upper layer B3 made of chromium oxide / chromium hydroxide.
  • the upper layer B3 made of chromium oxide / chromium hydroxide offers a good adhesive base for the organic material of the overlay.
  • the organic coating can be, for example, an organic lacquer or polymer films made from thermoplastic polymers such as PET, PE, PP or mixtures thereof.
  • the organic coating can be applied, for example, in a "coil coating" process or in a panel process, the coated metal strip being first divided into panels in the panel process, which are then coated with an organic lacquer or with a polymer film be coated.
  • FIG 2 a second embodiment of a strip coating system with eight electrolysis tanks 1a-1h arranged one behind the other in the strip running direction v is shown.
  • the electrolysis tanks 1a-1h are grouped into three groups, namely a front group with the first two electrolysis tanks 1a, 1b, a middle group with the subsequent electrolysis tanks 1c-1f in the direction of belt travel and a rear group with the last two electrolysis tanks 1g and 1h.
  • the first electrolyte solution E1 which contains organic complexing agents, in particular formates, is located in the front group of electrolysis tanks 1a, 1b and in the middle group of electrolysis tanks 1c, 1d, 1e, 1f.
  • the rear group of electrolysis tanks 1g, 1h is filled with the second electrolyte solution E2, which is free from organic substances and in particular free from complexing agents.
  • the coatings B preferably have a total weight of the chromium of at least 40 mg / m 2 and particularly preferably from 70 mg / m 2 to 180 mg / m 2 .
  • the coating B expediently has a total of chromium oxide with a weight of the chromium bound as chromium oxide or chromium hydroxide of at least 3 mg chromium per m 2 and in particular from 3 to 15 mg / m 2 .
  • the amount by weight of the chromium bound as chromium oxide or chromium hydroxide, averaged over the entire amount of coating B, is preferably at least 5 and preferably more than 7 mg of chromium per m 2 .
  • Good adhesion of organic paints or thermoplastic polymer materials on the surface of the coating B can be achieved with weight limits of the chromium oxide / chromium hydroxide of up to approx. 15 mg / m 2 .
  • One the preferred range for the weight of the chromium oxide / chromium hydroxide in coating B is therefore between 5 and 15 mg / m 2 .
  • the thickness or the weight of the individual layers B1, B2, B3 can be adjusted in the method according to the invention by means of the electrolysis times t1, t2. As soon as a sufficiently high current density is selected in the electrolysis tanks, the thickness or the weight of the deposited layers B1, B2, B3 does not depend on the current density but only on the electrolysis time t1, t2 (if the temperature of the electrolyte solution remains constant) the metal strip M is in electrolytically effective contact with the first or the second electrolyte solution E1, E2.
  • the chromium oxide / chromium hydroxide proportion of the total weight of the coating B can therefore be set by the electrolysis time t2, in which the metal strip M in the rear electrolysis tank 1c or the rear group of electrolysis tanks 1g, 1h is in electrolytically effective contact with the second electrolyte solution E2 is located.
  • This electrolysis duration t2 is in turn dependent on the dimensioning of the rear electrolysis tank 1c or 1g, 1h and the belt speed.

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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)
  • Inorganic Chemistry (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
EP20156814.4A 2019-04-09 2020-02-12 Procédé de fabrication d'une bande métallique revêtue d'un revêtement de chrome et d'oxyde de chrome à base d'une solution électrolytique avec un composé à base de chrome trivalent et système d'électrolyse permettant la mise en oeuvre dudit procédé Pending EP3733932A1 (fr)

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DE102019109356.2A DE102019109356A1 (de) 2019-04-09 2019-04-09 Verfahren zur Herstellung eines mit einer Beschichtung aus Chrom und Chromoxid beschichteten Metallbands auf Basis einer Elektrolytlösung mit einer dreiwertigen Chromverbindung und Elektrolysesystem zur Durchführung des Verfahrens

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DE102021125696A1 (de) * 2021-10-04 2023-04-06 Thyssenkrupp Rasselstein Gmbh Verfahren zur Passivierung der Oberfläche eines Weißblechs und Elektrolysesystem zur Durchführung des Verfahrens

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WO2014079909A1 (fr) 2012-11-21 2014-05-30 Tata Steel Ijmuiden B.V. Revêtements de chrome et d'oxyde de chrome appliqués à des substrats en acier pour des applications de conditionnement et procédé permettant de produire lesdits revêtements
WO2015037391A1 (fr) * 2013-09-12 2015-03-19 奥野製薬工業株式会社 Bain de placage de chrome trivalent
WO2015177314A1 (fr) 2014-05-21 2015-11-26 Tata Steel Ijmuiden B.V. Procédé permettant de plaquer une bande métallique mobile, et bande métallique revêtue ainsi produite
EP3146091A1 (fr) * 2014-05-21 2017-03-29 Tata Steel IJmuiden BV Procédé pour la fabrication de substrats revêtus de chrome-oxyde de chrome et substrats revêtus produits de cette manière
EP3666931A1 (fr) * 2018-12-13 2020-06-17 ThyssenKrupp Rasselstein GmbH Procédé de fabrication d'une bande métallique ayant un revêtement de chrome et d'oxyde de chrome avec un électrolyte à base de chromium trivalent

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IT1161593B (it) * 1983-03-03 1987-03-18 Lavezzari Impianti Spa Procedimento per la protezione di laminati piani di acciaio zincato mediante rivestimento elettrolitico multistrato
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EP2831314B1 (fr) * 2012-03-30 2016-05-18 Tata Steel IJmuiden B.V. Substrat revêtu pour applications d'emballage et procédé de production dudit substrat revêtu
CA2915523C (fr) * 2013-06-20 2017-09-12 Tata Steel Ijmuiden B.V. Procede permettant de fabriquer des substrats recouverts de chrome-d'oxyde de chrome
BR112019009702B1 (pt) * 2016-11-14 2023-03-28 Tata Steel Ijmuiden B.V. Método para a eletrogalvanização de uma tira de aço não revestida com uma camada de revestimento

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US5330605A (en) * 1990-03-16 1994-07-19 Toyo Kohan Co., Ltd. Method for production of a copolyester resin film laminated metal sheet
WO2014079909A1 (fr) 2012-11-21 2014-05-30 Tata Steel Ijmuiden B.V. Revêtements de chrome et d'oxyde de chrome appliqués à des substrats en acier pour des applications de conditionnement et procédé permettant de produire lesdits revêtements
WO2015037391A1 (fr) * 2013-09-12 2015-03-19 奥野製薬工業株式会社 Bain de placage de chrome trivalent
WO2015177314A1 (fr) 2014-05-21 2015-11-26 Tata Steel Ijmuiden B.V. Procédé permettant de plaquer une bande métallique mobile, et bande métallique revêtue ainsi produite
EP3146091A1 (fr) * 2014-05-21 2017-03-29 Tata Steel IJmuiden BV Procédé pour la fabrication de substrats revêtus de chrome-oxyde de chrome et substrats revêtus produits de cette manière
EP3666931A1 (fr) * 2018-12-13 2020-06-17 ThyssenKrupp Rasselstein GmbH Procédé de fabrication d'une bande métallique ayant un revêtement de chrome et d'oxyde de chrome avec un électrolyte à base de chromium trivalent

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CN111793809B (zh) 2023-08-08
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CA3075039A1 (fr) 2020-10-09
BR102020004554A2 (pt) 2020-10-20
JP2020172700A (ja) 2020-10-22
US20200325590A1 (en) 2020-10-15
DE102019109356A1 (de) 2020-10-15
CA3075039C (fr) 2022-05-17
CN111793809A (zh) 2020-10-20
KR20200119197A (ko) 2020-10-19

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