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EP2726650B1 - Electrolytic iron plating on zinc surfaces - Google Patents

Electrolytic iron plating on zinc surfaces Download PDF

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Publication number
EP2726650B1
EP2726650B1 EP20120725788 EP12725788A EP2726650B1 EP 2726650 B1 EP2726650 B1 EP 2726650B1 EP 20120725788 EP20120725788 EP 20120725788 EP 12725788 A EP12725788 A EP 12725788A EP 2726650 B1 EP2726650 B1 EP 2726650B1
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EP
European Patent Office
Prior art keywords
galvanized
acid
iron
alloy
galvanized steel
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.)
Not-in-force
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EP20120725788
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German (de)
French (fr)
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EP2726650A1 (en
Inventor
Michael Wolpers
Marcel Roth
Jürgen Stodt
Andreas Arnold
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Henkel AG and Co KGaA
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Henkel AG and Co KGaA
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Priority to PL12725788T priority Critical patent/PL2726650T3/en
Publication of EP2726650A1 publication Critical patent/EP2726650A1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/20—Electroplating: Baths therefor from solutions of iron
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/78—Pretreatment of the material to be coated
    • 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

Definitions

  • the present invention relates to a process for the metallizing pretreatment of galvanized and / or alloy-galvanized steel surfaces or assembled metallic components, which at least partially have surfaces of zinc, in which from a water-containing electrolyte containing water-soluble compounds, which are a source of iron cations, a thin layer support is deposited on iron on the zinc surfaces.
  • the method is carried out at least partially or permanently with the application of an electrolysis voltage, wherein the galvanized and / or alloy-galvanized steel surfaces are connected as a cathode.
  • the aqueous electrolyte additionally contains an accelerator selected from oxo acids of the elements phosphorus, nitrogen and / or sulfur, wherein the elements phosphorus, nitrogen and / or sulfur are present in middle oxidation states.
  • the prior art discloses methods for metallizing galvanized and / or alloy-galvanized steel surfaces. That's how it describes WO 2008/135478 a pretreatment process for the electroless deposition of metallic coatings, in particular of iron and tin, on galvanized and / or alloy-galvanized steel surfaces.
  • the pretreatment provides moderately metallized zinc surfaces, which is advantageous for the application of subsequent anticorrosive coatings and provides excellent edge protection.
  • the deposition of iron is preferably carried out from aqueous compositions which additionally contain accelerators based on oxo acids of the elements phosphorus and / or nitrogen in medium oxidation states.
  • Alloy-galvanized steel surfaces are according to the invention, characterized in that their surface has more than 50 at .-% zinc based on all metallic elements, wherein the surface fraction of zinc by X-ray photoelectron spectroscopy using Al K-alpha radiation (1486.6 eV) is to be determined ,
  • pretreatment is defined as the passivation by means of inorganic barrier layers (for example phosphating, chromating) or a process step preceding the lacquer coating for conditioning the cleaned metallic surface.
  • inorganic barrier layers for example phosphating, chromating
  • Such conditioning of the surface results in an improvement of the corrosion protection and the paint adhesion for the entire layer system resulting at the end of a process chain for the corrosion-protective surface treatment.
  • the specifying designation of the pretreatment as "metallising” is to be understood as meaning a pretreatment process which directly effects a metallic deposition of iron or an iron alloy on the zinc surface, after metallizing Pretreatment the pretreated metal surface is at least 50 At .-% of iron based on all metallic elements, wherein the proportion of metallic iron is at least 50%, the determination of the surface layer coating and the metallic state by means of X-ray photoelectron spectroscopy (XPS) using Al K-alpha radiation (1486.6 eV).
  • XPS X-ray photoelectron spectroscopy
  • the contact time or pretreatment time with the aqueous electrolyte should preferably be at least 1 second but not longer than 60 seconds, preferably not longer than 20 seconds.
  • the ratio of electrolysis time to contact time should preferably be at least 0.5, more preferably at least 0.8.
  • the cathodic electrolysis current can be applied potentiostatically or galvanostatically and in each case by pulses, with galvanostatic methods being preferred.
  • galvanostatic methods it is preferable that the galvanized or alloy-galvanized steel surface does not function as the anode during the contact time, so that no anodic electrolytic current is impressed.
  • the metallization is particularly effective when the concentration of water-soluble compounds which are a source of iron cations, based on the element iron in the electrolyte, is preferably at least 0.01 mol / l, but preferably 0.4 mol / l, more preferably 0.1 mol / l does not exceed.
  • the water-soluble compounds are preferably a source of iron (II) ions and thus preferably water-soluble salts selected from iron (II) sulfate, iron (II) nitrate, iron (II) lactate and / or iron (II) gluconate.
  • the iron ions in the electrolyte represent at least 50% iron (II) ions.
  • the accelerators with reduction action contained in the pretreatment process according to the invention for increasing the deposition rate of the iron cations, ie the metallization of the galvanized or alloy-galvanized surface are preferably selected from oxo acids of phosphorus.
  • Oxox acids of phosphorus are again preferably selected from hyposalpetriger acid, hypos nitric acid, nitrous acid, hypophosphoric acid, hypodiphosphonic acid, Diphosphorus (III, V) acid, phosphonic acid, diphosphonic acid and / or phosphinic acid and salts thereof, particularly preferably from phosphinic acid and salts thereof.
  • the molar ratio of accelerator to the concentration of the water-soluble compounds, which are a source of iron cations, in the aqueous electrolyte is preferably not greater than 2: 1, more preferably not greater than 1: 1 and preferably not below 1: 5, the Concentration of the water-soluble compounds, which are a source of iron cations, referred to the element iron.
  • the pH of the electrolyte should preferably not be less than 2, and preferably not greater than 6, in order, on the one hand, to minimize the acid corrosion of the zinc-containing substrate and, on the other hand, to ensure the stability of the iron (II) ions in the treatment solution.
  • the electrolyte containing the water-soluble compounds of iron may further contain chelating complexing agents with oxygen and / or nitrogen ligands for stabilization, surprisingly a faster kinetics of iron deposition is observed, so that a shorter contact time can be achieved with optimum iron occupancy of the galvanized surface.
  • Suitable chelating complexing agents are especially those which are selected from triethanolamine, diethanolamine, monoethanolamine, monoisopropanolamine, aminoethylethanolamine, 1-amino-2,3,4,5,6-pentahydroxyhexane, N- (hydroxyethyl) ethylenediaminetriacetic acid, Ethylenediaminetetraacetic acid, diethylenetriamine-pentaacetic acid, 1,2-diamino-propanetetraacetic acid, 1,3-diaminopropane-tetraacetic acid, tartaric acid, ascorbic acid, lactic acid, mucic acid, gallic acid, gluconic acid and / or glucoheptonic acid and their salts and stereoisomers as well as sorbitol, glucose and Glucamine and their stereoisomers.
  • a particularly effective formulation of the aqueous electrolyte is for the process according to the invention, when in this a molar ratio of chelating complexing agents to the concentration of water-soluble compounds which are a source of iron cations of not greater than 5: 1, preferably not greater 2: 1, but of at least 1: 5 is realized, wherein the concentration of the water-soluble compounds, which are a source of iron cations, based on the element iron.
  • the electrolyte for the metallizing pretreatment may additionally contain surfactants which are able to liberate the metallic surface from impurities without itself inhibiting the surface by forming compact adsorbate layers for the metallization.
  • Nonionic surfactants with average HLB values of at least 8 and at most 14 may be used for this purpose.
  • the electrolyte is essentially free of electropositive metal cations selected from cations of the elements Ni, Co, Cu, and / or Sn, since these compete with the deposition of the iron cations.
  • substantially free in this context, means that no water-soluble compounds that are a source of the electropositive metal cations are intentionally added to the electrolyte.
  • the treatment according to the invention of alloy-zinc plated steel surfaces containing electropositive metals as an alloy constituent or composite metal surfaces may cause small amounts of these elements to enter the electrolyte.
  • the electrolyte in the process according to the invention has a total of less than 2000 ppm of zinc ions, since zinc ions are able to displace the iron ions from their complexes in the presence of complexing agents according to a preferred embodiment of the invention.
  • a dipping process which is common in strip steel production and strip steel refinement is practicable.
  • layer deposits of preferably at least 1 mg / m 2 , but preferably not more than 100 mg / m 2 , and particularly preferably not more than 50 mg / m 2, based on the element iron result .
  • the layer support is defined as the area-related mass fraction of iron on the galvanized or alloy-galvanized steel surface immediately after the pretreatment according to the invention.
  • the pretreatment process according to the invention is based on the subsequent process steps of the surface treatment of galvanized and / or alloy-galvanized steel surfaces with regard to optimized corrosion protection and outstanding paint adhesion, especially tailored to cut edges, surface defects and bimetallic contacts. Consequently, the present invention encompasses various aftertreatment processes, ie conversion and lacquer coatings, which, in conjunction with the pretreatment described above, provide the desired results in terms of corrosion protection.
  • the invention therefore relates in a further aspect to the production of a passivating conversion coating on the metallized pretreated galvanized and / or alloy-galvanized steel surface with or without intermediate rinsing and / or drying step.
  • a chromium-containing or preferably chromium-free conversion solution can be used.
  • Preferred conversion solutions with which the metal surfaces pretreated according to the present invention can be treated prior to the application of a permanent corrosion-protective organic coating can be used DE-A-199 23 084 and the literature cited herein.
  • a chromium-free aqueous conversion agent besides hexafluoro anions of Ti, Si and / or Zr may contain as further active ingredients: phosphoric acid, one or more compounds of Co, Ni, V, Fe, Mn, Mo or W, a water-soluble or water-dispersible film-forming organic polymer or copolymer and organophosphonic acids that have complexing properties.
  • phosphoric acid one or more compounds of Co, Ni, V, Fe, Mn, Mo or W
  • water-soluble and / or water-dispersible polymeric complexing agents with oxygen and / or nitrogen ligands based on Mannich addition products of polyvinylphenols with formaldehyde and aliphatic amino alcohols may be present.
  • Such polymers are in the patent US 5,298,289 disclosed.
  • the process parameters for a conversion treatment in the context of this invention are to be chosen such that a conversion layer is produced, the per m 2 surface at least 0.05, preferably at least 0.2, but not more than 3, Contains 5, preferably not more than 2.0 and more preferably not more than 1.0 mmol of the metal M, which is the essential component of the conversion solution.
  • metals M are Cr (III), B, Si, Ti, Zr, Hf.
  • the coverage of the zinc surface with the metal M can be determined, for example, by an X-ray fluorescence method.
  • the chromium-free conversion medium additionally contains copper ions.
  • the molar ratio of metal atoms M selected from zirconium and / or titanium to copper atoms in such a conversion agent is preferably selected such that it produces a conversion layer in which at least 0.1 mmol, preferably at least 0.3 mmol, but not more than 2 mmol of copper are additionally included.
  • a method in which the metallizing pretreatment is followed by a conversion treatment to form a thin amorphous inorganic coating may also employ a method in which the metallization of the present invention comprises zinc phosphating to form a crystalline phosphate layer having a preferred coating weight of not less than 3 g / m 2 follows.
  • the metallizing pretreatment and the subsequent conversion treatment usually follow further process steps for the application of additional layers, in particular organic paints or coating systems.
  • the present invention relates to the galvanized and / or alloy-galvanized steel surface and the metallic component which consists at least partially of a zinc surface which has been metallized in the aqueous electrolyte according to the method of the invention or subsequently to this pretreatment with further passivating conversion layers and / or Lacquer is coated.
  • Such a treated steel surface or treated component is used in body construction in automotive manufacturing, shipbuilding, construction and for the production of white goods.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)

Description

Die vorliegende Erfindung betrifft ein Verfahren zur metallisierenden Vorbehandlung verzinkter und/oder legierungsverzinkter Stahloberflächen oder zusammengefügter metallischer Bauteile, die zumindest teilweise Oberflächen aus Zink aufweisen, bei dem aus einem wässrigen Elektrolyten enthaltend wasserlösliche Verbindungen, die eine Quelle für Eisen-Kationen darstellen, eine dünne Schichtauflage an Eisen auf die Zinkoberflächen abgeschieden wird. Das Verfahren wird zumindest partiell oder dauerhaft unter Anlegung einer Elektrolysespannung durchgeführt, wobei die verzinkten und/oder legierungsverzinkten Stahloberflächen als Kathode geschaltet sind. Der wässrige Elektrolyt enthält zusätzlich einen Beschleuniger ausgewählt aus Oxosäuren der Elemente Phosphor, Stickstoff und/oder Schwefel, wobei die Elemente Phosphor, Stickstoff und/oder Schwefel in mittleren Oxidationsstufen vorliegen.The present invention relates to a process for the metallizing pretreatment of galvanized and / or alloy-galvanized steel surfaces or assembled metallic components, which at least partially have surfaces of zinc, in which from a water-containing electrolyte containing water-soluble compounds, which are a source of iron cations, a thin layer support is deposited on iron on the zinc surfaces. The method is carried out at least partially or permanently with the application of an electrolysis voltage, wherein the galvanized and / or alloy-galvanized steel surfaces are connected as a cathode. The aqueous electrolyte additionally contains an accelerator selected from oxo acids of the elements phosphorus, nitrogen and / or sulfur, wherein the elements phosphorus, nitrogen and / or sulfur are present in middle oxidation states.

Im Stand der Technik sind Verfahren zur Metallisierung von verzinkten und/oder legierungsverzinkten Stahloberflächen bekannt. So beschreibt die WO 2008/135478 ein Vorbehandlungsverfahren zur stromlosen Abscheidung metallischer Überzüge, insbesondere von Eisen und Zinn, auf verzinkten und/oder legierungsverzinkten Stahloberflächen. Die Vorbehandlung liefert moderat metallisierte Zinkoberflächen, die für die Aufbringung nachfolgender Korrosionsschutzschichten vorteilhaft ist und einen hervorragenden Kantenschutz bedingt. Die Abscheidung von Eisen erfolgt dabei bevorzugt aus wässrigen Zusammensetzungen, die zusätzlich Beschleuniger auf Basis von Oxosäuren der Elemente Phosphor und/oder Stickstoff in mittleren Oxidationsstufen enthalten. Es hat sich in der Praxis der Vorbehandlung herausgestellt, dass die Abscheidung metallischer Überzüge aus derartigen Zusammensetzungen zu einer signifikanten Anreicherung von Zink-Ionen im Vor-behandlungsbad führt. Gleichzeitig wird eine starke Abnahme der Effektivität der Metall-abscheidung beobachtet, der durch Zudosierung weiterer Mengen des Beschleunigers und abzuscheidender Metall-Kationen entgegengewirkt werden kann. Die Aufgabe der vorliegenden Erfindung besteht nun darin, die Performance des Vorbehandlungsbades über einen längeren Zeitraum stabil zu halten, wobei auf eine Zudosierung von Aktivkomponenten des Abscheidebades möglichst verzichtet werden kann.The prior art discloses methods for metallizing galvanized and / or alloy-galvanized steel surfaces. That's how it describes WO 2008/135478 a pretreatment process for the electroless deposition of metallic coatings, in particular of iron and tin, on galvanized and / or alloy-galvanized steel surfaces. The pretreatment provides moderately metallized zinc surfaces, which is advantageous for the application of subsequent anticorrosive coatings and provides excellent edge protection. The deposition of iron is preferably carried out from aqueous compositions which additionally contain accelerators based on oxo acids of the elements phosphorus and / or nitrogen in medium oxidation states. It has been found in the practice of pretreatment that deposition of metallic coatings from such compositions results in significant enrichment of zinc ions in the pre-treatment bath. At the same time a strong decrease in the effectiveness of the metal deposition is observed, which can be counteracted by metering in additional amounts of the accelerator and metal cations to be deposited. The object of the present invention is now to keep the performance of the pre-treatment bath stable over a longer period of time, which can be dispensed as possible with a metered addition of active components of the deposition bath.

Diese Aufgabe wurde gelöst durch ein Verfahren zur metallisierenden Vorbehandlung von verzinkten oder legierungsverzinkten Stahloberflächen, wobei die verzinkte oder legierungsverzinkte Stahloberfläche als Kathode mit einem wässrigen Elektrolyten in Kontakt gebracht wird, dessen pH-Wert nicht größer als 9 ist, dadurch gekennzeichnet, dass im wässrigen Elektrolyten

  • (a)mindestens eine wasserlösliche Verbindung, die eine Quelle für Eisen-Kationen darstellt, wobei die Gesamtkonzentration an derartigen Verbindungen mindestens 0,001 mol/l bezogen auf das Element Eisen beträgt,
  • (b)mindestens einen Beschleuniger ausgewählt aus Oxosäuren von Phosphor, Stickstoff oder Schwefel sowie deren Salzen, wobei mindestens ein Phosphor-, Stickstoff-, oder Schwefelatom der jeweiligen Oxosäure in einer mittleren Oxidationsstufe vorliegt, und
  • c) insgesamt weniger als 10 ppm an elektropositiven Metall-Kationen ausgewählt aus Kationen der Elemente Ni, Co, Cu, Sn enthalten sind,
wobei die verzinkte oder legierungsverzinkte Stahloberfläche während der Kontaktzeit mit dem wässrigen Elektrolyten zumindest zeitweise als Kathode geschaltet wird, wobei der verzinkten oder legierungsverzinkten Stahloberfläche in dieser Zeit ein kathodischer Elektrolysestrom aufgeprägt wird, der zumindest 0,001 mAcm-2, vorzugsweise mindestens 0,01 mAcm-2, jedoch nicht größer 500 mAcm-2, vorzugsweise nicht größer als 50 mAcm-2 ist.This object has been achieved by a method for the metallizing pre-treatment of galvanized or alloy-galvanized steel surfaces, wherein the galvanized or Alloy-galvanized steel surface is brought as a cathode in contact with an aqueous electrolyte whose pH is not greater than 9, characterized in that in the aqueous electrolyte
  • (a) at least one water-soluble compound which is a source of iron cations, the total concentration of such compounds being at least 0.001 mol / l, based on the element iron,
  • (B) at least one accelerator selected from oxo acids of phosphorus, nitrogen or sulfur and their salts, wherein at least one phosphorus, nitrogen, or sulfur atom of the respective oxo acid is present in a middle oxidation state, and
  • c) a total of less than 10 ppm of electropositive metal cations selected from cations of the elements Ni, Co, Cu, Sn are contained,
wherein the galvanized or alloy-galvanized steel surface is at least temporarily connected as a cathode during the contact time with the aqueous electrolyte, wherein the galvanized or alloy-galvanized steel surface in this time a cathodic electrolytic current is impressed which at least 0.001 mAcm -2 , preferably at least 0.01 mAcm -2 but not greater than 500 mAcm -2 , preferably not greater than 50 mAcm -2 .

Das erfindungsgemäße Verfahren eignet sich für sämtliche Metalloberflächen, beispielsweise Bandstahl, und/oder zusammengefügten metallischen Bauteile, die zumindest teilweise auch aus Zinkoberflächen bestehen, beispielsweise Automobilkarosserien. Legierungsverzinkte Stahloberflächen sind erfindungsgemäß, darin gekennzeichnet, dass deren Oberfläche mehr als 50 At.-% Zink bezogen auf alle metallischen Elemente aufweist, wobei der Oberflächenanteil an Zink mittels Röntgenphotoelektronenspektroskopie unter Verwendung von Al K-alpha Strahlung (1486,6 eV) zu bestimmen ist.The method according to the invention is suitable for all metal surfaces, for example strip steel, and / or assembled metallic components, which at least partially also consist of zinc surfaces, for example automobile bodies. Alloy-galvanized steel surfaces are according to the invention, characterized in that their surface has more than 50 at .-% zinc based on all metallic elements, wherein the surface fraction of zinc by X-ray photoelectron spectroscopy using Al K-alpha radiation (1486.6 eV) is to be determined ,

Unter Vorbehandlung wird im Sinne dieser Erfindung ein der Passivierung mittels anorganischer Barriereschichten (z.B. Phosphatierung, Chromatierung) oder ein der Lackbeschichtung vorausgehender Prozessschritt zur Konditionierung der gereinigten metallischen Oberfläche bezeichnet. Eine solche Konditionierung der Oberfläche bewirkt für das gesamte, am Ende einer Prozesskette zur korrosionsschützenden Oberflächen-behandlung resultierende Schichtsystem eine Verbesserung des Korrosionsschutzes und der Lackhaftung.For the purposes of this invention, pretreatment is defined as the passivation by means of inorganic barrier layers (for example phosphating, chromating) or a process step preceding the lacquer coating for conditioning the cleaned metallic surface. Such conditioning of the surface results in an improvement of the corrosion protection and the paint adhesion for the entire layer system resulting at the end of a process chain for the corrosion-protective surface treatment.

In der spezifizierenden Bezeichnung der Vorbehandlung als "metallisierend" ist ein Vorbehandlungsprozess zu verstehen, der unmittelbar eine metallische Abscheidung von Eisen oder einer Eisenlegierung auf der Zinkoberfläche bewirkt, wobei nach erfolgter metallisierender Vorbehandlung die vorbehandelte Metalloberfläche zumindest zu 50 At.-% aus Eisen bezogen auf alle metallischen Elemente besteht, wobei der Anteil an metallischem Eisen bei zumindest 50 % liegt, wobei die Bestimmung der oberflächlichen Schichtauflage und des metallischen Zustandes mittels Röntgen-photo-elektronen-spektroskopie (XPS) unter Verwendung von Al K-alpha Strahlung (1486,6 eV) erfolgen kann.The specifying designation of the pretreatment as "metallising" is to be understood as meaning a pretreatment process which directly effects a metallic deposition of iron or an iron alloy on the zinc surface, after metallizing Pretreatment the pretreated metal surface is at least 50 At .-% of iron based on all metallic elements, wherein the proportion of metallic iron is at least 50%, the determination of the surface layer coating and the metallic state by means of X-ray photoelectron spectroscopy (XPS) using Al K-alpha radiation (1486.6 eV).

Die Kontaktzeit oder Vorbehandlungsdauer mit dem wässrigen Elektrolyten sollte vorzugsweise mindestens 1 Sekunde, aber nicht länger als 60 Sekunden, vorzugsweise nicht länger als 20 Sekunden betragen. Das Verhältnis von Elektrolysedauer zur Kontaktzeit sollte vorzugsweise zumindest 0,5, besonders bevorzugt zumindest 0,8 betragen.The contact time or pretreatment time with the aqueous electrolyte should preferably be at least 1 second but not longer than 60 seconds, preferably not longer than 20 seconds. The ratio of electrolysis time to contact time should preferably be at least 0.5, more preferably at least 0.8.

Die Applikation des kathodischen Elektrolysestroms kann im erfindungsgemäßen Verfahren potentiostatisch oder galvanostatisch und jeweils durch Pulsen erfolgen, wobei galvanostatische Verfahren bevorzugt sind. Insbesondere ist es bevorzugt, dass die verzinkte oder legierungsverzinkte Stahloberfläche während der Kontaktzeit nicht als Anode fungiert, so dass kein anodischer Elektrolysestrom aufgeprägt wird.In the method according to the invention, the cathodic electrolysis current can be applied potentiostatically or galvanostatically and in each case by pulses, with galvanostatic methods being preferred. In particular, it is preferable that the galvanized or alloy-galvanized steel surface does not function as the anode during the contact time, so that no anodic electrolytic current is impressed.

Es zeigt sich, dass die Metallisierung besonders effektiv ist, wenn die Konzentration an wasserlöslichen Verbindungen, die eine Quelle für Eisen-Kationen sind, bezogen auf das Element Eisen im Elektrolyten vorzugsweise mindestens 0,01 mol/l beträgt, aber vorzugsweise 0,4 mol/l, besonders bevorzugt 0,1 mol/l nicht überschreitet.It is found that the metallization is particularly effective when the concentration of water-soluble compounds which are a source of iron cations, based on the element iron in the electrolyte, is preferably at least 0.01 mol / l, but preferably 0.4 mol / l, more preferably 0.1 mol / l does not exceed.

Vorzugsweise sind die wasserlöslichen Verbindungen eine Quelle für Eisen(II)-Ionen und somit vorzugsweise wasserlösliche Salze ausgewählt aus Eisen(II)sulfat, Eisen(II)nitrat, Eisen(II)lactat und/oder Eisen(II)gluconat.The water-soluble compounds are preferably a source of iron (II) ions and thus preferably water-soluble salts selected from iron (II) sulfate, iron (II) nitrate, iron (II) lactate and / or iron (II) gluconate.

In diesem Zusammenhang ist es weiterhin bevorzugt, dass die Eisen-Ionen im Elektrolyten zumindest zu 50 % Eisen(II)-Ionen darstellen.In this context, it is further preferred that the iron ions in the electrolyte represent at least 50% iron (II) ions.

Die im erfindungsgemäßen Vorbehandlungsverfahren zur Erhöhung der Abscheidungsrate der Eisen-Kationen, also der Metallisierung der verzinkten oder legierungsverzinkten Oberfläche, enthaltenen Beschleuniger mit Reduktionswirkung sind vorzugsweise ausgewählt aus Oxosäuren von Phosphor. Derartige Oxoxsäuren sind wiederum vorzugsweise ausgewählt aus hyposalpetriger Säure, Hyposalpetersäure, salpetriger Säure, Hypophosphorsäure, Hypodiphosphonsäure, Diphosphor(III, V)-säure, Phosphonsäure, Diphosphonsäure und/oder Phosphinsäure und deren Salze, besonders bevorzugt aus Phosphinsäure sowie deren Salze. Das molare Verhältnis von Beschleuniger zur Konzentration der wasserlöslichen Verbindungen, die eine Quelle für Eisen-Kationen darstellen, ist im wässrigen Elektrolyten vorzugsweise nicht größer als 2:1, besonders bevorzugt nicht größer als 1:1 und unterschreitet vorzugsweise 1:5 nicht, wobei die Konzentration der wasserlöslichen Verbindungen, die eine Quelle für Eisen-Kationen darstellen, auf das Element Eisen bezogen wird.The accelerators with reduction action contained in the pretreatment process according to the invention for increasing the deposition rate of the iron cations, ie the metallization of the galvanized or alloy-galvanized surface, are preferably selected from oxo acids of phosphorus. Such Oxoxsäuren are again preferably selected from hyposalpetriger acid, hypos nitric acid, nitrous acid, hypophosphoric acid, hypodiphosphonic acid, Diphosphorus (III, V) acid, phosphonic acid, diphosphonic acid and / or phosphinic acid and salts thereof, particularly preferably from phosphinic acid and salts thereof. The molar ratio of accelerator to the concentration of the water-soluble compounds, which are a source of iron cations, in the aqueous electrolyte is preferably not greater than 2: 1, more preferably not greater than 1: 1 and preferably not below 1: 5, the Concentration of the water-soluble compounds, which are a source of iron cations, referred to the element iron.

Der pH-Wert des Elektrolyten sollte vorzugsweise nicht kleiner als 2 und vorzugsweise nicht größer als 6, um einerseits die Säurekorrosion des zinkhaltigen Substrates zu minimieren und andererseits die Stabilität der Eisen(II)-Ionen in der Behandlungslösung zu gewährleisten.The pH of the electrolyte should preferably not be less than 2, and preferably not greater than 6, in order, on the one hand, to minimize the acid corrosion of the zinc-containing substrate and, on the other hand, to ensure the stability of the iron (II) ions in the treatment solution.

Der die wasserlöslichen Verbindungen von Eisen enthaltende Elektrolyt kann zur Stabilisierung ferner chelatisierende Komplexbildner mit Sauerstoff- und/oder Stickstoff-Liganden enthalten, wobei überraschenderweise eine schnellere Kinetik der Eisenabscheidung beobachtet wird, so dass eine kürzere Kontaktzeit bei optimaler Eisenbelegung der verzinkten Oberfläche erzielt werden kann.The electrolyte containing the water-soluble compounds of iron may further contain chelating complexing agents with oxygen and / or nitrogen ligands for stabilization, surprisingly a faster kinetics of iron deposition is observed, so that a shorter contact time can be achieved with optimum iron occupancy of the galvanized surface.

Als chelatisierende Komplexbildner kommen dabei speziell solche in Frage, die ausgewählt sind aus Triethanolamin, Diethanolamin, Monoethanolamin, Monoisopropanolamin, Aminoethylethanolamin, 1-Amino-2,3,4,5,6-pentahydroxyhexan, N-(Hydroxyethyl)-ethylendiamintri-essigsäure, Ethylendiamintetraessigsäure, Diethylentriamin-pentaessigsäure, 1,2-Diamino-propantetraessigsäure, 1,3-Diaminopropan-tetraessigsäure, Weinsäure, Ascorbinsäure, Milch-säure, Schleimsäure, Gallussäure, Gluconsäure und/oder Glucoheptonsäure sowie deren Salze und Stereoisomere als auch Sorbit, Glucose und Glucamin sowie deren Stereoisomere.Suitable chelating complexing agents are especially those which are selected from triethanolamine, diethanolamine, monoethanolamine, monoisopropanolamine, aminoethylethanolamine, 1-amino-2,3,4,5,6-pentahydroxyhexane, N- (hydroxyethyl) ethylenediaminetriacetic acid, Ethylenediaminetetraacetic acid, diethylenetriamine-pentaacetic acid, 1,2-diamino-propanetetraacetic acid, 1,3-diaminopropane-tetraacetic acid, tartaric acid, ascorbic acid, lactic acid, mucic acid, gallic acid, gluconic acid and / or glucoheptonic acid and their salts and stereoisomers as well as sorbitol, glucose and Glucamine and their stereoisomers.

Eine besonders effektive Formulierung des wässrigen Elektrolyten besteht für das erfindungsgemäße Verfahren dann, wenn in diesem ein molares Verhältnis von chelatisierenden Komplexbildnern zur Konzentration an wasserlöslichen Verbindungen, die eine Quelle für Eisen-Kationen sind, von nicht größer ist als 5:1, vorzugsweise nicht größer 2:1, aber von mindestens 1:5 realisiert ist, wobei die Konzentration der wasserlöslichen Verbindungen, die eine Quelle für Eisen-Kationen darstellen, auf das Element Eisen bezogen wird. Geringere molare Verhältnisse als erhöhen die Abscheiderate bezogen auf das Element Eisen nur unwesentlich. Ähnliches gilt für höhere molare Verhältnisse als 5:1, bei denen ein hoher Anteil an freien Komplexbildner vorliegt.A particularly effective formulation of the aqueous electrolyte is for the process according to the invention, when in this a molar ratio of chelating complexing agents to the concentration of water-soluble compounds which are a source of iron cations of not greater than 5: 1, preferably not greater 2: 1, but of at least 1: 5 is realized, wherein the concentration of the water-soluble compounds, which are a source of iron cations, based on the element iron. Lower molar ratios than increase the deposition rate based on the element iron only insignificantly. The same applies to higher molar ratios than 5: 1, in which a high proportion of free complexing agent is present.

Darüber hinaus kann der Elektrolyt für die metallisierende Vorbehandlung zusätzlich Tenside enthalten, die die metallische Oberfläche von Verunreinigungen zu befreien vermag, ohne selbst die Oberfläche durch die Ausbildung kompakter Adsorbatschichten für die Metallisierung zu inhibieren. Hierfür können vorzugsweise Niotenside mit mittleren HLB-Werten von mindestens 8 und höchstens 14 eingesetzt werden.In addition, the electrolyte for the metallizing pretreatment may additionally contain surfactants which are able to liberate the metallic surface from impurities without itself inhibiting the surface by forming compact adsorbate layers for the metallization. Nonionic surfactants with average HLB values of at least 8 and at most 14 may be used for this purpose.

In einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens ist der Elektrolyt im Wesentlichen frei von elektropositiven Metall-Kationen ausgewählt aus Kationen der Elemente Ni, Co, Cu, und/oder Sn, da diese in Konkurrenz zur Abscheidung der Eisen-Kationen treten. Im Wesentlichen frei, bedeutet in diesem Zusammenhang, dass dem Elektrolyten keine wasserlöslichen Verbindungen, die eine Quelle für die elektropositiven Metall-Kationen darstellen, absichtlich hinzugesetzt werden. Die erfindungsgemäße Behandlung legierungsverzinkter Stahloberflächen, die elektropositive Metalle als Legierungsbestandteil enthalten, oder metallischer Oberflächen in Verbundkonstruktion kann bewirken, dass geringe Mengen dieser Elemente in den Elektrolyten gelangen.In a preferred embodiment of the method according to the invention, the electrolyte is essentially free of electropositive metal cations selected from cations of the elements Ni, Co, Cu, and / or Sn, since these compete with the deposition of the iron cations. Substantially free, in this context, means that no water-soluble compounds that are a source of the electropositive metal cations are intentionally added to the electrolyte. The treatment according to the invention of alloy-zinc plated steel surfaces containing electropositive metals as an alloy constituent or composite metal surfaces may cause small amounts of these elements to enter the electrolyte.

Ebenfalls bevorzugt ist, dass der Elektrolyt im erfindungsgemäßen Verfahren insgesamt weniger als 2000 ppm an Zink-Ionen aufweist, da Zink-Ionen die Eisen-Ionen in Anwesenheit von Komplexbildner gemäß einer bevorzugten Ausführungsform der Erfindung aus ihren Komplexen zu verdrängen vermögen.It is likewise preferred that the electrolyte in the process according to the invention has a total of less than 2000 ppm of zinc ions, since zinc ions are able to displace the iron ions from their complexes in the presence of complexing agents according to a preferred embodiment of the invention.

Für das erfindungsgemäße Vorbehandlungsverfahren, welches einen Teil der Prozesskette der Oberflächenbehandlung von verzinkten und/oder legierungsverzinkten Stahloberflächen darstellt, ist ein in der Bandstahlherstellung und Bandstahlveredelung gängige Tauchverfahren praktikabel.For the pretreatment process according to the invention, which forms part of the process chain of the surface treatment of galvanized and / or alloy-galvanized steel surfaces, a dipping process which is common in strip steel production and strip steel refinement is practicable.

Bei erfindungsgemäßer Ausführung des Verfahrens ist es bevorzugt, dass Schichtauflagen von vorzugsweise mindestens 1 mg/m2, aber von vorzugsweise nicht mehr als 100 mg/m2, und besonders bevorzugt von nicht mehr als 50 mg/m2 bezogen auf das Element Eisen resultieren. Die Schichtauflage ist im Sinne der vorliegenden Erfindung definiert als flächenbezogener Massenanteil an Eisen auf der verzinkten oder legierungsverzinkten Stahloberfläche unmittelbar nach der erfindungsgemäßen Vorbehandlung.When carrying out the method according to the invention, it is preferred that layer deposits of preferably at least 1 mg / m 2 , but preferably not more than 100 mg / m 2 , and particularly preferably not more than 50 mg / m 2, based on the element iron result , For the purposes of the present invention, the layer support is defined as the area-related mass fraction of iron on the galvanized or alloy-galvanized steel surface immediately after the pretreatment according to the invention.

Das erfindungsgemäße Vorbehandlungsverfahren ist auf die nachfolgenden Prozessschritte der Oberflächenbehandlung von verzinkten und/oder legierungsverzinkten Stahloberflächen hinsichtlich eines optimierten Korrosionsschutzes und einer hervorragenden Lackhaftung insbesondere an Schnittkanten, Oberflächendefekten und Bimetallkontakten abgestimmt. Konsequenterweise werden von der vorliegenden Erfindung verschiedene Nachbehandlungsverfahren, also Konversions- und Lackbeschichtungen, umfasst, die in Verbindung mit der zuvor beschriebenen Vorbehandlung die gewünschten Ergebnisse hinsichtlich des Korrosionsschutzes liefern.The pretreatment process according to the invention is based on the subsequent process steps of the surface treatment of galvanized and / or alloy-galvanized steel surfaces with regard to optimized corrosion protection and outstanding paint adhesion, especially tailored to cut edges, surface defects and bimetallic contacts. Consequently, the present invention encompasses various aftertreatment processes, ie conversion and lacquer coatings, which, in conjunction with the pretreatment described above, provide the desired results in terms of corrosion protection.

Die Erfindung betrifft daher in einem weiteren Aspekt die Erzeugung einer passivierenden Konversionsbeschichtung auf der metallisierend vorbehandelten verzinkten und/oder legierungsverzinkten Stahloberfläche mit oder ohne dazwischenliegendem Spül- und/oder Trocknungsschritt.The invention therefore relates in a further aspect to the production of a passivating conversion coating on the metallized pretreated galvanized and / or alloy-galvanized steel surface with or without intermediate rinsing and / or drying step.

Hierfür kann eine chromhaltige oder vorzugsweise chromfreie Konversionslösung eingesetzt werden. Bevorzugte Konversionslösungen, mit denen die gemäß der vorliegenden Erfindung vorbehandelten Metalloberflächen vor den Aufbringen einer permanent korrosionsschützenden organischen Beschichtung behandelt werden können, können der DE-A-199 23 084 und der hierin zitierten Literatur entnommen werden. Nach dieser Lehre kann ein chromfreies wässriges Konversionsmittel außer Hexafluoro-Anionen von Ti, Si und/oder Zr als weitere Wirkstoffe enthalten: Phosphorsäure, eine oder mehrere Verbindungen von Co, Ni, V, Fe, Mn, Mo oder W, ein wasserlösliches oder wasserdispergierbares filmbildendes organisches Polymer oder Copolymer und Organophosphonsäuren, die komplexierende Eigenschaften haben. Auf Seite 4 dieses Dokuments ist in Zeilen 17 bis 39 eine ausführliche Liste organischer filmbildender Polymere aufgeführt, die in den genannten Konversionslösungen enthalten sein können.For this purpose, a chromium-containing or preferably chromium-free conversion solution can be used. Preferred conversion solutions with which the metal surfaces pretreated according to the present invention can be treated prior to the application of a permanent corrosion-protective organic coating can be used DE-A-199 23 084 and the literature cited herein. According to this teaching, a chromium-free aqueous conversion agent besides hexafluoro anions of Ti, Si and / or Zr may contain as further active ingredients: phosphoric acid, one or more compounds of Co, Ni, V, Fe, Mn, Mo or W, a water-soluble or water-dispersible film-forming organic polymer or copolymer and organophosphonic acids that have complexing properties. On page 4 of this document, a detailed list of organic film-forming polymers which may be included in said conversion solutions is given in lines 17-39.

Im Anschluss hieran offenbart dieses Dokument eine sehr umfangreiche Liste komplexbildender Organophosphonsäuren als weitere mögliche Komponenten der Konversionslösungen. Konkrete Beispiele dieser Komponenten können der genannten DE-A-199 23 084 entnommen werden.Following this, this document discloses a very extensive list of complex-forming organophosphonic acids as further possible components of the conversion solutions. Concrete examples of these components may be mentioned DE-A-199 23 084 be removed.

Des Weiteren können wasserlösliche und/oder wasserdispergierbare polymere Komplexbildner mit Sauerstoff- und/oder Stickstoff-Liganden auf der Basis von Mannich-Additionsprodukten von Polyvinylphenolen mit Formaldehyd und aliphatischen Aminoalkoholen enthalten sein. Derartige Polymere sind in der Patentschrift US 5,298,289 offenbart.Furthermore, water-soluble and / or water-dispersible polymeric complexing agents with oxygen and / or nitrogen ligands based on Mannich addition products of polyvinylphenols with formaldehyde and aliphatic amino alcohols may be present. Such polymers are in the patent US 5,298,289 disclosed.

Die Verfahrensparameter für eine Konversionsbehandlung im Sinne dieser Erfindung wie beispielsweise Behandlungstemperatur, Behandlungsdauer und Kontaktzeit sind dabei derart zu wählen, dass eine Konversionsschicht erzeugt wird, die pro m2 Oberfläche mindestens 0,05, vorzugsweise mindestens 0,2, aber nicht mehr als 3,5, vorzugsweise nicht mehr als 2,0 und besonders bevorzugt nicht mehr als 1,0 mmol des Metalls M enthält, das die wesentliche Komponente der Konversionslösung darstellt. Beispiele für Metalle M sind Cr(III), B, Si, Ti, Zr, Hf. Die Belegungsdichte der Zinkoberfläche mit dem Metall M kann beispielsweise mit einer Röntgenfluoreszenzmethode ermittelt werden.The process parameters for a conversion treatment in the context of this invention, such as treatment temperature, treatment time and contact time are to be chosen such that a conversion layer is produced, the per m 2 surface at least 0.05, preferably at least 0.2, but not more than 3, Contains 5, preferably not more than 2.0 and more preferably not more than 1.0 mmol of the metal M, which is the essential component of the conversion solution. Examples of metals M are Cr (III), B, Si, Ti, Zr, Hf. The coverage of the zinc surface with the metal M can be determined, for example, by an X-ray fluorescence method.

In einem besonderen Aspekt eines erfindungsgemäßen Verfahrens, das eine der metallisierenden Vorbehandlung folgende Konversionsbehandlung umfasst, enthält das chromfreie Konversionsmittel zusätzlich Kupfer-Ionen. Das molare Verhältnis von Metallatomen M ausgewählt aus Zirkon und/oder Titan zu Kupferatomen in einem solchen Konversionsmittel ist dabei vorzugsweise derart gewählt, dass dieses eine Konversionsschicht erzeugt, in der mindestens 0,1 mmol, vorzugsweise mindestens 0,3 mmol, aber nicht mehr als 2 mmol Kupfer zusätzlich enthalten sind.In a particular aspect of a method according to the invention, which comprises a conversion treatment following the metallizing pretreatment, the chromium-free conversion medium additionally contains copper ions. The molar ratio of metal atoms M selected from zirconium and / or titanium to copper atoms in such a conversion agent is preferably selected such that it produces a conversion layer in which at least 0.1 mmol, preferably at least 0.3 mmol, but not more than 2 mmol of copper are additionally included.

Die vorliegende Erfindung betrifft also auch ein Verfahren (IIa), welches folgende Prozessschritte einschließlich der metallisierenden Vorbehandlung und einer Konversionsbehandlung der verzinkten und/oder legierungsverzinkten Stahloberfläche umfasst:

  1. i) gegebenenfalls Reinigung / Entfettung der Werkstoffoberfläche
  2. ii) metallisierende Vorbehandlung mit einem wässrigen Mittel (1) gemäß der vorliegenden Erfindung
  3. iii) gegebenenfalls Spül- und/oder Trocknungsschritt
  4. iv) chrom(VI)freie Konversionsbehandlung, bei der eine Konversionsschicht erzeugt wird, die pro m2 Oberfläche 0,05 bis 3,5 mmol des Metalls M enthält, das die wesentliche Komponente der Konversionslösung darstellt, wobei die Metalle M ausgewählt sind aus Cr(III), B, Si, Ti, Zr, Hf.
The present invention thus also relates to a process (IIa) which comprises the following process steps, including the metallizing pretreatment and a conversion treatment of the galvanized and / or alloy-galvanized steel surface:
  1. i) optionally cleaning / degreasing the material surface
  2. ii) metallizing pretreatment with an aqueous agent (1) according to the present invention
  3. iii) optionally rinsing and / or drying step
  4. iv) chromium (VI) free conversion treatment in which a conversion layer containing, per m 2 of surface area, 0.05 to 3.5 mmol of the metal M which is the essential component of the conversion solution, the metals M being selected from Cr (III), B, Si, Ti, Zr, Hf.

Alternativ kann zu einem Verfahren, in dem der metallisierenden Vorbehandlung eine Konversionsbehandlung unter Ausbildung einer dünnen amorphen anorganischen Beschichtung folgt, auch ein Verfahren angewandt werden, in dem der erfindungsgemäßen Metallisierung eine Zinkphosphatierung unter Ausbildung einer kristallinen Phosphatschicht mit einem bevorzugten Schichtgewicht von nicht weniger als 3 g/m2 folgt.Alternatively, a method in which the metallizing pretreatment is followed by a conversion treatment to form a thin amorphous inorganic coating may also employ a method in which the metallization of the present invention comprises zinc phosphating to form a crystalline phosphate layer having a preferred coating weight of not less than 3 g / m 2 follows.

Darüber hinaus schließen sich der metallisierenden Vorbehandlung und der nachfolgenden Konversionsbehandlung üblicherweise weitere Verfahrensschritte zur Aufbringung zusätzlicher Schichten, insbesondere organischer Lacke oder Lacksysteme an.In addition, the metallizing pretreatment and the subsequent conversion treatment usually follow further process steps for the application of additional layers, in particular organic paints or coating systems.

Die vorliegende Erfindung betrifft in einem weiteren Aspekt die verzinkte und/oder legierungsverzinkte Stahloberfläche sowie das metallische Bauteil, welches zumindest teilweise aus einer Zinkoberfläche besteht, das gemäß dem erfindungsgemäßen Verfahren im wässrigen Elektrolyten metallisierend vorbehandelt ist oder nachfolgend dieser Vorbehandlung mit weiteren passivierenden Konversionsschichten und/oder Lacken beschichtet ist.In a further aspect, the present invention relates to the galvanized and / or alloy-galvanized steel surface and the metallic component which consists at least partially of a zinc surface which has been metallized in the aqueous electrolyte according to the method of the invention or subsequently to this pretreatment with further passivating conversion layers and / or Lacquer is coated.

Eine derartig behandelte Stahloberfläche oder behandeltes Bauteil findet Verwendung im Karosseriebau bei der automobilen Fertigung, im Schiffsbau, im Baugewerbe sowie für die Herstellung Weißer Ware.Such a treated steel surface or treated component is used in body construction in automotive manufacturing, shipbuilding, construction and for the production of white goods.

Claims (11)

  1. Method for the metallizing pretreatment of galvanized or alloy-galvanized steel surfaces, wherein the galvanized or alloy-galvanized steel surface is brought into contact with an aqueous electrolyte whose pH-value is not greater than 9, characterized in that the aqueous electrolyte contains
    (a) at least one water-soluble compound which is a source for iron cations, wherein the overall concentration of such compounds is at least 0.001 mol/L, based on the element iron,
    (b) at least one accelerator selected from oxoacids of phosphorus, nitrogen, or sulfur and the salts thereof, wherein at least one phosphorus, nitrogen, or sulfur atom of the respective oxoacid is present in a medium oxidation state, and
    c) less than 10 ppm total of electropositive metal cations selected from cations of the elements Ni, Co, Cu, Sn,
    wherein the galvanized or alloy-galvanized steel surface is at least temporarily connected as the cathode during the contact time with the aqueous electrolyte, the galvanized or alloy-galvanized steel surface being acted on during this time by a cathodic electrolysis current in the range of 0.001 to 500 mAcm-2.
  2. Method according to one or both of Claims 1 and 2, characterized in that the water-soluble compounds, which are a source for iron cations, are present in the electrolyte in an overall concentration of at least 0.01 mol/L, but do not exceed an overall concentration of 0.4 mol/L, preferably 0.1 mol/L, in the electrolyte, in each case based on the element iron.
  3. Method according to one or more of the preceding claims, characterized in that the iron ions are at least 50% iron(II) ions.
  4. Method according to one or more of the preceding claims, characterized in that the pH-value of the electrolyte is not less than 2 and is not greater than 6.
  5. Method according to one or more of the preceding claims, characterized in that the aqueous agent additionally contains at least one chelating complexing agent with oxygen and/or nitrogen ligands.
  6. Method according to Claim 5, characterized in that the chelating complexing agents are selected from triethanolamine, diethanolamine, monoethanolamine, monoisopropanolamine, aminoethylethanolamine, 1-amino-2,3,4,5,6-pentahydroxyhexane, N-(hydroxyethyl)ethylenediamine triacetic acid, ethylenediamine tetraacetic acid,
    diethylenetriamine pentaacetic acid, 1,2-diaminopropane tetraacetic acid, 1,3-diaminopropane tetraacetic acid, ascorbic acid, tartaric acid, lactic acid, muric acid, gluconic acid, and/or glucoheptonic acid, and the salts thereof and stereoisomers, as well as sorbitol, glucose, and glucamine and the stereoisomers thereof.
  7. Method according to one or both of Claims 5 and 6, characterized in that the molar ratio of chelating complexing agents to cations of iron is not greater than 5:1, preferably not greater than 2:1, but is at least 1:5.
  8. Method according to one or more of Claims 1 to 7, characterized in that the electrolyte contains no more than 2000 ppm of zinc ions.
  9. Method according to one or more of Claims 1 to 8, characterized in that after the galvanized or alloy-galvanized steel surface is brought into contact with the aqueous agent, a metallic coating containing metal (A) is present in a coating layer weight of at least 1 mg/m2, but not greater than 100 mg/m2, preferably not greater than 50 mg/m2.
  10. Method according to one or more of Claims 1 to 9, characterized in that after the galvanized or alloy-galvanized steel surface is brought into contact with the aqueous agent, with or without a rinsing and/or drying step in between, a passivating conversion treatment of the galvanized or alloy-galvanized steel surface subjected to metallizing pretreatment is carried out.
  11. Method according to Claim 10, characterized in that the method is followed by further method steps for applying additional layers, in particular conversion layers, organic lacquers, and/or coating systems.
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US20130206603A1 (en) 2013-08-15
CA2840117C (en) 2019-07-02
DE102011078258A1 (en) 2013-01-03
KR20140037149A (en) 2014-03-26
CN103764878B (en) 2016-06-15
AU2012278121B2 (en) 2016-07-21
US9309602B2 (en) 2016-04-12
JP2014518332A (en) 2014-07-28
EP2726650A1 (en) 2014-05-07
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WO2013000674A1 (en) 2013-01-03
AU2012278121A1 (en) 2014-01-16

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