EP1624090A1 - Procedé de dépot électrolytique simultané de magnésium et de zinc sur un substrat métallique et procédé pour la fabrication d'articles métalliques laqués protégés contre la corrosion - Google Patents

Procedé de dépot électrolytique simultané de magnésium et de zinc sur un substrat métallique et procédé pour la fabrication d'articles métalliques laqués protégés contre la corrosion Download PDF

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Publication number
EP1624090A1
EP1624090A1 EP05016373A EP05016373A EP1624090A1 EP 1624090 A1 EP1624090 A1 EP 1624090A1 EP 05016373 A EP05016373 A EP 05016373A EP 05016373 A EP05016373 A EP 05016373A EP 1624090 A1 EP1624090 A1 EP 1624090A1
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EP
European Patent Office
Prior art keywords
sheet
zinc
sheet metal
magnesium
solvent
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.)
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EP05016373A
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German (de)
English (en)
Inventor
Horst Dr. Mittelstädt
Cetin Dr. Nazikkol
Bernd Dr. Schuhmacher
Christian Dipl.-Phys. Schwerdt
Stefan Dr. Wienströer
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 Steel Europe AG
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ThyssenKrupp Steel AG
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Publication date
Application filed by ThyssenKrupp Steel AG filed Critical ThyssenKrupp Steel AG
Publication of EP1624090A1 publication Critical patent/EP1624090A1/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
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/565—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of zinc

Definitions

  • the invention relates to a process for the simultaneous electrolytic deposition of zinc and magnesium on a substrate made of sheet metal, in particular sheet steel, in a non-aqueous solvent with pKa ⁇ 16.
  • the invention further relates to a method for producing a corrosion-protected painted molded part from sheet metal, in particular sheet steel.
  • the galvanizing of steel body panels for the purpose of corrosion protection has largely prevailed in recent decades.
  • the galvanized in the hot dip process or by electrodeposition in an aqueous electrolyte steel sheets are characterized by a good adhesion of the zinc layer on the steel sheet and a good processability and by a very good surface quality.
  • An electrolytic deposition of magnesium in an aqueous electrolyte precludes the strong negative normal potential of magnesium (-2,363 V), so that in an electrolytic cell filled with an aqueous electrolyte at the cathode instead of the deposition of elemental magnesium almost exclusively the reduction of protons Hydrogen gas occurs.
  • EP 1 036 862 A1 describes the electrolytic deposition of a Zn-Mg alloy layer on a metal sheet consisting of iron, an iron alloy or copper, aluminum or titanium or their alloys, in an aqueous-acidic electrolyte nonionic or cationic surfactant is added.
  • the electrodeposited alloy layer is characterized according to the information in this document by good formability and corrosion resistance. The latter is increased by the incorporation of carbon from the organic surfactant.
  • a disadvantage of this method is its low current efficiency, since the charge transport in the electrolyte takes place to a considerable extent via protons and thus the formation of gaseous hydrogen in the course of magnesium deposition can not be prevented. This must be compensated either by increasing the current density or the residence time of the sheet to be coated in the electrolysis cell, which leads in both cases to a reduction in process efficiency.
  • the invention has for its object to provide a method for the simultaneous electrolytic deposition of zinc and magnesium on a substrate made of sheet metal, especially steel, specify which is highly efficient and is characterized accordingly by low cost.
  • a coated according to the method sheet metal part should have excellent corrosion properties and at the same time be characterized by a particularly good formability.
  • This object is achieved by a method of the type mentioned above in that in the electrolytic deposition of zinc and magnesium on the substrate without heat treatment, an alloy layer is formed.
  • the decisive advantage of the method according to the invention is that the Mg-Zn alloy formation takes place without heat treatment and a coating layer of zinc is not a prerequisite for this alloy formation. Since no heat treatment takes place, the formability of the sheet substrate is not affected.
  • a coated sheet according to the invention is characterized by the superficial deposited magnesium by excellent corrosion resistance and by a practically unchanged compared to the untreated sheet formability.
  • the deposited on the substrate surface layer contains a 3-phase mixture of elemental Mg, elemental Zn and a MgZn2 alloy phase.
  • Optimum results in terms of corrosion resistance, surface quality and formability are achieved if the layer deposited on the substrate surface contains about 15-30% Mg and about 70-85% Zn.
  • the pKa of the solvent is ⁇ 30.
  • the proton concentration is so low that comparatively low current densities are sufficient to operate the process with high process speed and efficiency.
  • the use of an aprotic solvent with pKa> 30 is particularly preferred.
  • Aprotic solvents are among the nonaqueous solvents which do not contain an ionizable proton in the molecule.
  • Suitable aprotic solvents are, for example, long-chain alcohols or hydrocarbons.
  • a proton-passivating substance is added to the solvent. This is particularly useful if the pKa of the solvent is only slightly above 16, especially if a protic solvent is used. As a result, the current density and the voltage can be lowered further. It is a matter of course that the proton-passivating substance is soluble in the particular solvent used.
  • the proton passivating substance may be a nonionic substance from the group of polyethylene glycols, polyoxyethylene alkyl ethers and polyoxyethylene-polyoxypropylene alkyl ethers. Likewise, however, the use of a cationic substance from the group primary, secondary, tertiary amines, quaternary ammonium salts and heterocyclic compounds is possible.
  • the inventive method can be operated with high current efficiency, since the charge carriers provided at the cathode can be used almost exclusively for the reduction of dissolved in the electrolyte zinc and magnesium ions.
  • the set current density is preferably between 6,000 and 15,000 A / m 2 .
  • the deposition takes place on a galvanized steel sheet.
  • the thickness of the zinc coating is for example about 3.5 microns and the thickness of the deposited layer about 0.05 microns to 1 micron.
  • moldings of any geometry can be produced, which provide excellent corrosion protection with high quality of the surface and at the same time high strength.
  • This is achieved by the sequence of the individual method steps selected according to the invention.
  • the surface of the still unformed sheet metal part is coated with a layer containing zinc and magnesium according to the method described above.
  • the thus coated sheet already has the mentioned high corrosion resistance and surface quality, but still has a low strength, so that it can easily be brought into the desired shape using known forming methods, such as deep drawing.
  • the coated sheet is formed.
  • the molding is painted with a baked enamel. This is followed by baking the applied lacquer layer, which is typically carried out at a temperature of about 200 ° C.
  • the applied lacquer layer cures.
  • the sheet substrate is subjected to a bake hardening process at this temperature, in which it almost completely loses its formability, ie solidifies. As a result, it is thus possible to produce a painted molded part in the desired geometry, which, in addition to the good corrosion and surface properties mentioned, is also distinguished by high dimensional stability.
  • a substrate in the form of a galvanized steel strip 1 in a transport direction T is passed through a roller guide 2 through an electrolytic cell.
  • the thickness of the zinc coating of the steel strip is preferably about 3.5 microns.
  • the electrolytic cell comprises a container 3 filled with a nonaqueous solvent 4 having a pKa ⁇ 16. This is preferably an aprotic solvent (pKa> 30) in the form of a long-chain alcohol.
  • pKa> 30 in the form of a long-chain alcohol.
  • zinc and magnesium salts are dissolved to provide a sufficient ion concentration.
  • an anode 5 of elemental zinc and an anode 6 of elemental magnesium are immersed in the solvent 4.
  • the galvanized steel strip 1 acts as the cathode of the electrolysis cell.
  • the anodes 5, 6 continuously release Zn or Mg ions into the solvent, which preferentially deposit on the surface of the galvanized steel strip as a 3-phase mixture of elemental Mg, elemental Zn and MgZn2 alloy phase.
  • the thickness of the layer and the respective Zn or Mg content in the layer by adjusting the element-specific current densities which are preferably between 6,000 and 15,000 A / m 2 , on the one hand between the Zn electrode 5 and the steel strip 1 and the Mg electrode 6 and the steel strip 1, on the other hand, are adjusted in tension as well as by the belt speed.
  • the thickness of the deposited layer is preferably 0.05 .mu.m to 1 .mu.m with a magnesium content of about 15 to 30 percent and corresponding to a zinc content of about 70 to 85 percent.
  • Fig. 2 the individual process steps for producing a corrosion-protected painted molded part made of sheet steel are shown.
  • a first step (I) is first in the manner described above a Mg-Zn coating electrolytically applied to a galvanized steel strip.
  • the corrosion properties of the steel strip are significantly improved with unchanged good formability.
  • the coated steel strip is then divided into individual sheet metal sections.
  • the coated sheet metal sections by means of a conventional forming process, such as deep drawing, reshaped (step II) and subsequently painted with a baked enamel (step III).
  • the latter can be done by various known methods, such as spraying or dip coating.
  • a painted molded part in the desired geometry can be produced, which is characterized by optimum corrosion and surface properties and by a high dimensional stability.

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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)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
EP05016373A 2004-08-04 2005-07-28 Procedé de dépot électrolytique simultané de magnésium et de zinc sur un substrat métallique et procédé pour la fabrication d'articles métalliques laqués protégés contre la corrosion Withdrawn EP1624090A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE200410037673 DE102004037673B4 (de) 2004-08-04 2004-08-04 Verfahren zur simultanen elektrolytischen Abscheidung von Zink und Magnesium auf einem Substrat aus Blech und Verfahren zur Herstellung eines korrosionsgeschützten lackierten Formteils aus Blech

Publications (1)

Publication Number Publication Date
EP1624090A1 true EP1624090A1 (fr) 2006-02-08

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EP05016373A Withdrawn EP1624090A1 (fr) 2004-08-04 2005-07-28 Procedé de dépot électrolytique simultané de magnésium et de zinc sur un substrat métallique et procédé pour la fabrication d'articles métalliques laqués protégés contre la corrosion

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EP (1) EP1624090A1 (fr)
DE (1) DE102004037673B4 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090053555A1 (en) * 2006-03-20 2009-02-26 Koichi Nose High Corrosion Resistance Hot dip Galvanized Steel Material

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008004728A1 (de) 2008-01-16 2009-07-23 Henkel Ag & Co. Kgaa Phosphatiertes Stahlblech sowie Verfahren zur Herstellung eines solchen Blechs

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58144492A (ja) * 1982-02-18 1983-08-27 Nobuyasu Doi 亜鉛−マグネシウム合金電気めつき浴
US4801363A (en) * 1987-01-05 1989-01-31 The Dow Chemical Company High purity alkaline earths via electrodeposition
EP1036862A1 (fr) 1999-03-15 2000-09-20 Kabushiki Kaisha Kobe Seiko Sho Tôle métallique électroplaquée au zinc-magnesium et procédé pour sa fabrication
WO2004053203A2 (fr) 2002-12-10 2004-06-24 Thyssenkrupp Stahl Ag Procede de depot electrolytique de magnesium sur une tole galvanisee

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58144492A (ja) * 1982-02-18 1983-08-27 Nobuyasu Doi 亜鉛−マグネシウム合金電気めつき浴
US4801363A (en) * 1987-01-05 1989-01-31 The Dow Chemical Company High purity alkaline earths via electrodeposition
EP1036862A1 (fr) 1999-03-15 2000-09-20 Kabushiki Kaisha Kobe Seiko Sho Tôle métallique électroplaquée au zinc-magnesium et procédé pour sa fabrication
WO2004053203A2 (fr) 2002-12-10 2004-06-24 Thyssenkrupp Stahl Ag Procede de depot electrolytique de magnesium sur une tole galvanisee

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Section Ch Week 198340, Derwent World Patents Index; Class M11, AN 1983-780034, XP002352873, "Zinc-magnesium alloy plating bath-contains ions of divalent zinc, divalent magnesium, chloride and/or sulphate, and borofluoric acid and/or silicon-fluoric acid" *
PATENT ABSTRACTS OF JAPAN vol. 007, no. 263 (C - 196) 24 November 1983 (1983-11-24) *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090053555A1 (en) * 2006-03-20 2009-02-26 Koichi Nose High Corrosion Resistance Hot dip Galvanized Steel Material
US8663818B2 (en) * 2006-03-20 2014-03-04 Nippon Steel & Sumitomo Metal Corporation High corrosion resistance hot dip galvanized steel material

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Publication number Publication date
DE102004037673A1 (de) 2006-03-16
DE102004037673B4 (de) 2009-01-29

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