EP3722464A1 - Procédé de passivation de la surface d'une tôle noire ou d'une tôle blanche et système d'électrolyse permettant la mise en oeuvre dudit procédé - Google Patents

Procédé de passivation de la surface d'une tôle noire ou d'une tôle blanche et système d'électrolyse permettant la mise en oeuvre dudit procédé Download PDF

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Publication number
EP3722464A1
EP3722464A1 EP20156810.2A EP20156810A EP3722464A1 EP 3722464 A1 EP3722464 A1 EP 3722464A1 EP 20156810 A EP20156810 A EP 20156810A EP 3722464 A1 EP3722464 A1 EP 3722464A1
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EP
European Patent Office
Prior art keywords
chromium
electrolyte solution
passivation layer
electrolysis
oxide
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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
EP20156810.2A
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German (de)
English (en)
Inventor
Andrea Dr. Marmann
Christoph Molls
Sebastian Hartung
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ThyssenKrupp Rasselstein GmbH
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ThyssenKrupp Rasselstein GmbH
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Publication of EP3722464A1 publication Critical patent/EP3722464A1/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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/38—Chromatising
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/005—Apparatus specially adapted for electrolytic conversion coating
    • 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
    • C25D21/00—Processes for servicing or operating cells for electrolytic coating
    • C25D21/12—Process control or regulation
    • 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
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/08—Electroplating with moving electrolyte e.g. jet electroplating
    • 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
    • C25D7/0628—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
    • C25D7/0642—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
    • C25D9/08—Electrolytic coating other than with metals with inorganic materials by cathodic processes

Definitions

  • the invention relates to a method for passivating the surface of a black plate or a tin plate by electrolytic deposition of a chromium oxide-containing passivation layer on the surface, as well as an electrolysis system for the electrolytic deposition of a chromium and chromium oxide-containing passivation layer on the surface of a black plate or a tin plate.
  • steel sheets which are electrolytically coated with a passivation layer of chromium and chromium oxide / chromium hydroxide are known from the prior art, which are known as tin-free steel sheet ("Tin Free Steel", TFS) or as “Electrolytic Chromium Coated Steel (ECCS)" and represent an alternative to tinplate.
  • TFS Tin Free Steel
  • ECCS Electrolytic Chromium Coated Steel
  • These tin-free steel sheets are particularly characterized by good adhesion for paints or organic 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 .
  • Tinned steel sheets are usually provided with a passivation layer after electrolytic tinning in order to prevent the tin surface from being oxidized by atmospheric oxygen.
  • Chromium-containing layers have proven to be suitable passivation layers, which can be deposited electrolytically from a chromium (VI) -containing electrolyte on the tin surface of tinplate.
  • These chromium-containing passivation layers are composed of metallic chromium and chromium oxides. Chromium oxide is understood to mean all compounds of chromium and oxygen, including chromium hydroxides.
  • electrolytic Coating methods are known with which a metallic chromium and chromium oxide / chromium hydroxide-containing passivation layer can be applied to a strip-shaped substrate (uncoated sheet steel or tinplate) in a coil coating system using an electrolyte containing chromium VI.
  • a metallic chromium and chromium oxide / chromium hydroxide-containing passivation layer can be applied to a strip-shaped substrate (uncoated sheet steel or tinplate) in a coil coating system using an electrolyte containing chromium VI.
  • these coating processes due to the properties of the chromium VI-containing electrolytes used in the electrolysis process, which are hazardous to the environment and health, 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 passivation layer made of chromium metal and chromium oxide can be deposited in layers in successive electrolysis tanks or in strip coating systems arranged one after the other, the electrolysis tanks each being filled with the same electrolyte solution.
  • the electrolytically deposited passivation layer can contain chromium sulfates and chromium carbides in addition to the components chromium metal and chromium oxide / chromium hydroxide, and that the proportions of these components in the total weight of the passivation layer depends to a large extent on the current densities set in the electrolysis tanks.
  • metallic chromium with a weight fraction of up to 80% (based on the total weight of the passivation layer) is deposited on the steel substrate and above the second current density threshold (regime III) the passivation layer contains a higher one Proportion of chromium oxide, which makes up between 1 ⁇ 4 and 1/3 of the total weight of the passivation layer in the area of higher current densities.
  • the values of the current density thresholds that delimit 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 therefore to provide an electrolysis process that is as efficient, inexpensive and environmentally friendly as possible for passivating the surface of black plate or tin plate with a chromium oxide / chromium hydroxide-containing passivation layer based on an electrolyte solution with a trivalent chromium compound.
  • 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.
  • black or tinplate coated according to the process have the highest possible resistance to oxidation in an oxygen-containing environment, in particular in atmospheric oxygen, and a good adhesive base for organic coatings, such as for organic paints and for polymer layers, in particular for polymer films, e.g. made of PET, PE or PP.
  • a chromium oxide-containing passivation layer is electrolytically applied from an electrolyte solution containing a trivalent chromium compound and at least one salt to increase the conductivity and at least one acid or a base to set a desired pH value onto an uncoated or tinned steel strip ( Blackplate or tinplate tape), the electrolyte solution containing no other constituents apart from the trivalent chromium compound and the at least one salt and the at least one acid or base and in particular being free of organic complexing agents and free of buffering agents.
  • No chromium VI-containing substances are used, not even as intermediate products, so that the process is completely free of chromium VI-containing substances and is therefore environmentally friendly and health-friendly when carrying out the process.
  • a layer of pure chromium oxide / chromium hydroxide forming the surface of the passivation layer is advantageous with regard to the oxidation resistance and the adhesive effect of organic coatings such as paints or polymer layers. It is therefore provided in the method according to the invention that in the electrolyte solution (Organic) complexing agents, in particular formates such as sodium or potassium formate, are dispensed with.
  • the passivation layer electrolytically deposited with such an electrolyte on the surface of the black plate or tin plate strip consists at least essentially of pure chromium oxide and / or chromium hydroxide.
  • 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 electrolytically applied passivation layer preferably has the highest possible weight fraction of chromium oxide, including chromium hydroxides.
  • the proportion by weight of chromium oxide and / or chromium hydroxides is preferably more than 90% and particularly preferably more than 95%. On the one hand, this ensures good passivation against oxidation of the surface of the black plate or tinplate and, on the other hand, offers 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 black plate or tin plate strip is connected as a cathode in at least one electrolysis tank and brought into contact with the electrolyte solution for a predetermined electrolysis time.
  • the electrolysis time is preferably in the range from 0.3 to 5.0 seconds and particularly preferably between 0.6 and 1.5 seconds.
  • the blackplate or tinplate strip is passed through at least one electrolysis tank or successively through several electrolysis tanks arranged one behind the other in the direction of belt travel at a specified belt speed, the belt speed preferably being at least 100 m / min and particularly 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 thickness or weight of the passivation layer made of chromium oxide can be controlled via the electrolysis time and thus via the belt speed.
  • the electrolysis time is preferably selected so that the deposited chromium oxide has a weight coverage of at least 3 mg / m 2 and preferably from 7 mg / m 2 to 10 mg / m 2 .
  • a weight of the chromium oxide in the passivation layer of at least 5 mg / m 2 , preferably more than 7 mg / m 2 is preferred.
  • a layer of an organic material, in particular an organic material, which adheres well to the chromium oxide layer of the passivation layer can therefore be used without problems after the electrolytic application of the passivation layer Lacquer or a thermoplastic material, in particular a polymer film made of PET, PE, PP or a mixture thereof, can be applied by painting the surface of the passivation layer with an organic lacquer or providing it with a plastic layer made of a thermoplastic material such as PET, PP and / or PE becomes.
  • a suitable anode is expediently selected for the electrolytic deposition of the passivation layer and placed in the electrolysis tank, which oxidizes chromium (III) from the trivalent chromium compound of the electrolyte solution to chromium ( VI) prevents.
  • anodes with an outer surface or a passivation layer 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 particularly suitable.
  • 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 passivation layer made of a mixed metal oxide.
  • anodes with a core made of titanium and an outer passivation layer made of a tantalum oxide-iridium oxide have proven to be suitable.
  • polarographic measurements showed that no Cr (VI) was produced.
  • the electrolyte solution preferably has a temperature in the range from 20 ° C to 65 ° C and particularly preferably in the range from 30 ° C to 55 ° C and in particular between 35 ° C and 45 ° C. At these temperatures, the electrolytic deposition of the chromium oxide-containing passivation layer is very efficient.
  • the temperature of the electrolyte solution or the temperature in an electrolysis tank is spoken of, what is meant in each case is the mean temperature which is averaged over the entire volume of the electrolysis tank. As a rule, there is a temperature gradient in the electrolysis tank with a temperature increase from top to bottom.
  • the electrolyte solution contains at least one conductivity-increasing salt and at least one acid or base for setting a suitable pH value and is preferably free from chloride ions and free from buffering agents, in particular free from a boric acid buffer.
  • the trivalent chromium compound of the 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 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.
  • the electrolyte solution contains at least one salt, which is preferably an alkali metal sulfate, in particular potassium or sodium sulfate.
  • a very efficient deposition of a chromium oxide-containing passivation layer is achieved if the pH value (measured at a temperature of 20 ° C.) of the electrolyte solution is in a range from 2.3 to 5.0 and preferably between 2.5 and 2.9 .
  • the desired pH can be adjusted by adding an acid or base to the 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.
  • compositions of the electrolyte solution each include basic Cr (III) sulfate (Cr 2 (SO 4 ) 3 ) as a trivalent chromium compound, and sodium sulfate as a conductivity-increasing salt and sulfuric acid to set a preferred pH value in the range from 2.3 to 5, 0.
  • the electrolyte solution contains no further components. This ensures simple and inexpensive production of the 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 electrolyte solution does not contain any complexing agents, the solution obtained in this way 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.
  • black sheets or tin sheets with a chromium oxide-containing passivation layer can be produced, the passivation layer at least essentially only consisting of chromium oxide and / or chromium hydroxide, preferably only of trivalent chromium oxides and / or chromium hydroxides, and preferably a proportion by weight of chromium oxide and / or chromium hydroxide of more than 90%, particularly preferably of more than 95%.
  • Such black sheets or tin sheets 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 passivation layer preferably contains at least essentially only compounds of chromium and oxygen in which the chromium is present in trivalent form, in particular as Cr 2 O 3 and / or Cr (OH) 3 .
  • the passivation layer can contain unavoidable impurities as well as residual components of chromium sulfate (as the starting chromium compound of the electrolytic deposition process).
  • the passivation layer is preferably composed of at least a first layer facing the surface of the black plate or tin plate and a second layer forming the surface of the passivated black or tin plate, the first layer containing metallic chromium and the second layer except for the mentioned residual components of chromium sulfate and unavoidable impurities consist of pure chromium oxide and / or chromium hydroxide.
  • a particularly good corrosion resistance of the black plates or tin plates according to the invention can be achieved if the passivation layer has a total weight of chromium oxide and / or chromium hydroxide of at least 3 mg / m 2 , preferably from 5 mg / m 2 to 15 mg / m 2 .
  • FIG. 1 a coil coating system for performing the method according to the invention is shown schematically.
  • 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 black plate strip or a tin-plated steel strip (tinplate strip) (hereinafter referred to as strip B) is passed through the electrolysis tanks 1a-1c.
  • the strip B 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).
  • Current rollers S are arranged above the electrolysis tanks 1a-1c, via which the belt B is connected as a cathode.
  • each electrolysis tank there is also a deflection roller U, around which the strip B is guided and is thereby directed into and out of the respective 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 tape B 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 strip B 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.
  • strip B is first degreased, rinsed, pickled and rinsed again and then passed through electrolysis tanks 1a-1c in this pretreated form, strip B being connected as a cathode by supplying electrical current via current rollers S.
  • the belt speed at which the belt B is guided through the electrolysis tanks 1a-1c is at least 100 m / min and can be up to 900 m / min.
  • the electrolysis tanks 1a to 1c arranged one behind the other in the direction of travel of the strip are each filled with the same electrolyte solution E.
  • the electrolyte solution E contains a trivalent chromium compound, preferably basic Cr (III) sulfate, Cr 2 (SO 4 ) 3 .
  • the electrolyte solution E also contains a salt, in particular an alkali metal sulfate, for example potassium or sodium sulfate, and an acid or base for setting a suitable pH.
  • the pH of the first electrolyte solution E is adjusted to a preferred value between 2.0 and 5.0 by adding the acid or base.
  • the concentration of the trivalent chromium compound in the electrolyte solution E is preferably at least 10 g / l and particularly preferably 20 g / l or more.
  • the temperature of the electrolyte solution E is expediently the same in the electrolysis tanks 1a, 1b, 1c and is preferably between 25.degree. C. and 70.degree. However, different temperatures of the electrolyte solution can also be set in the electrolysis tanks 1a, 1b, 1c.
  • the temperature of the electrolyte solution in the middle electrolysis tank 1b can be lower than in the upstream, front electrolysis tank 1a.
  • the temperature of the electrolyte solution in the middle electrolysis tank 1b is, for example, between 25 ° C and 37 ° C and in particular 35 ° C and the temperature of the electrolyte solution E in the front electrolysis tank 1a is between 40 ° C and 75 ° C and in particular at 55 ° C.
  • the electrolyte solution E contains no organic components and in particular no complexing agents.
  • the electrolyte solution E is also free from halides and buffering agents such as boric acid.
  • 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 belt B which is connected as a cathode and passed through the electrolysis tanks 1a-1c, is in electrolytically effective contact with the electrolyte solution E during an electrolysis period tl, t2 or t3 in the electrolysis tanks 1a, 1b, 1c.
  • the electrolysis time tl, t2, t3 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 + t3, during which the strip B is in electrolytically effective contact with electrolyte solution E 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 strip B in each electrolysis tank 1a, 1b, 1c, which is at least essentially made of chromium oxide and / or chromium hydroxide and, if a sulfate-containing electrolyte solution E is used, may contain chromium sulfate.
  • a layer B1, B2, B3 is produced in each of the electrolysis tanks 1a, 1b, 1c, the composition of the layers B1, B2, B3 being at least essentially the same if the electrolyte solution E is contained in the electrolysis tank 1a-1c and the same Electrolysis parameters, especially the same current densities and temperatures, are used.
  • the proportion by weight of chromium oxide / chromium hydroxide in the weight of layers B1, B2 and B3 and accordingly also in the total weight of the coating, which is composed of these layers B1, B2 and B3, is expediently at least 90%, preferably more than 95% %.
  • FIG 2 is a schematic sectional view of a strip B electrolytically coated using the method according to the invention.
  • a passivation layer P which is composed of the individual layers B1, B2, B3, is applied to one side of the strip B.
  • Each individual layer B1, B2, B3 is applied to the surface in one of the electrolysis tanks 1a, 1b, 1c.
  • the layer structure of the layers B1, B2, B3 deposited on the tape can be demonstrated by GDOES spectra ( Glow Discharge Optical Emission Spectroscopy ).
  • a metallic chromium layer with a thickness of 10-15 is formed on strip B in the electrolysis tanks 1a, 1b, 1c, depending on the duration of the electrolysis nm is deposited.
  • the surface of these layers oxidizes after the deposition and is mainly present as chromium oxide in the form Cr 2 O 3 or as mixed oxide hydroxide in the form 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, B3 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 3 ).
  • FIG 4 a GDOES spectrum of a tape B is shown which has been passivated with the method according to the invention using an electrolyte solution E, the electrolyte solution E not containing any organic complexing agents such as formates. It can be seen that a layer (passivation layer) is deposited on strip B, which at least essentially only consists of chromium oxide / chromium hydroxide and possibly also contains small amounts of chromium sulfate.
  • the composition of the passivation layer 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 strip B provided with the passivation layer can be rinsed, dried and oiled (for example with DOS). Then the strip B electrolytically coated with the passivation layer can additionally be provided with an organic coating.
  • the organic edition is in a known manner, for example.
  • By painting or lamination of a Plastic film is applied to the surface of the passivation layer, i.e. to the upper layer B3 made of chromium oxide.
  • the chromium oxide surface of layer B3 provides 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 strip being first divided into panels in the panel process, which are then coated with an organic paint or with a polymer film be coated.
  • the passivation layers applied with the method according to the invention preferably have a total weight of chromium oxide / chromium hydroxide of at least 3 mg / m 2 and preferably of at least 5 mg / m 2 .
  • Good adhesion of organic lacquers or thermoplastic polymer materials on the surface of the passivation layer B can be achieved with weight limits of the chromium oxide / chromium hydroxide of up to approx. 15 mg / m 2 .
  • a preferred range for the weight of the chromium oxide / chromium hydroxide in the passivation layer is therefore between 3 and 15 mg / m 2 and a particularly preferred range is between 5 and 15 mg / m 2
  • the thickness or the weight of the individual layers B1, B2, B3 can be set in the illustrated embodiment of the method according to the invention by the electrolysis times t1, t2, t3 and the current density in the electrolysis tanks. 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 depends linearly on the current density and (if the temperature of the electrolyte solution remains the same) linearly on the electrolysis time tl, t2, t3 in the electrolysis tanks in which the band B is in contact with the electrolytic solution E in an electrolytically effective manner.
  • the weight of the passivation layer can therefore be adjusted by the duration of the electrolysis and / or the current density in which the strip B is in contact with the electrolyte solution E in an electrolytically effective manner.
  • the electrolysis time t is in turn dependent on the dimensioning of the electrolysis tanks and the belt speed.

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  • Electroplating And Plating Baths Therefor (AREA)
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EP20156810.2A 2019-04-09 2020-02-12 Procédé de passivation de la surface d'une tôle noire ou d'une tôle blanche et système d'électrolyse permettant la mise en oeuvre dudit procédé Pending EP3722464A1 (fr)

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DE102019109354.6A DE102019109354A1 (de) 2019-04-09 2019-04-09 Verfahren zur Passivierung der Oberfläche eines Schwarzblechs oder eines Weißblechs und Elektrolysesystem zur Durchführung des Verfahrens

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US (1) US20200325591A1 (fr)
EP (1) EP3722464A1 (fr)
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KR (1) KR20200119194A (fr)
CN (1) CN111793815A (fr)
BR (1) BR102020004546A2 (fr)
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DE (1) DE102019109354A1 (fr)

Cited By (1)

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EP4159896A2 (fr) 2021-10-04 2023-04-05 ThyssenKrupp Rasselstein GmbH Procédé de passivation de la surface d'une tôle étamée et système d'électrolyse destiné à la mise en uvre du procédé

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WO2015037391A1 (fr) * 2013-09-12 2015-03-19 奥野製薬工業株式会社 Bain de placage de chrome trivalent
WO2015177315A1 (fr) 2014-05-21 2015-11-26 Tata Steel Ijmuiden B.V. Procédé pour la fabrication de substrats revêtus de chrome-oxyde de chrome et substrats revêtus produits de cette manière
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

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FR2465011A1 (fr) * 1979-09-06 1981-03-20 Carnaud Sa Materiau constitue d'une tole d'acier protegee, son procede de fabrication, et ses applications, ntamment aux boites de conserve
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GB1318311A (en) * 1969-07-09 1973-05-31 Uss Eng & Consult Can stock with differential protective coatings
US6099714A (en) * 1996-08-30 2000-08-08 Sanchem, Inc. Passification of tin surfaces
WO2015037391A1 (fr) * 2013-09-12 2015-03-19 奥野製薬工業株式会社 Bain de placage de chrome trivalent
WO2015177315A1 (fr) 2014-05-21 2015-11-26 Tata Steel Ijmuiden B.V. Procédé pour la fabrication de substrats revêtus de chrome-oxyde de chrome et substrats revêtus produits de cette manière
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

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4159896A2 (fr) 2021-10-04 2023-04-05 ThyssenKrupp Rasselstein GmbH Procédé de passivation de la surface d'une tôle étamée et système d'électrolyse destiné à la mise en uvre du procédé
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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CA3075010C (fr) 2022-05-17
KR20200119194A (ko) 2020-10-19
BR102020004546A2 (pt) 2020-10-20
US20200325591A1 (en) 2020-10-15
CA3075010A1 (fr) 2020-10-09
JP2020172701A (ja) 2020-10-22
CN111793815A (zh) 2020-10-20
DE102019109354A1 (de) 2020-10-15

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