EP2215285B1 - Zirconium phosphating of metal components, in particular iron - Google Patents

Zirconium phosphating of metal components, in particular iron Download PDF

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EP2215285B1
EP2215285B1 EP08853163.7A EP08853163A EP2215285B1 EP 2215285 B1 EP2215285 B1 EP 2215285B1 EP 08853163 A EP08853163 A EP 08853163A EP 2215285 B1 EP2215285 B1 EP 2215285B1
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Prior art keywords
ppm
zirconium
less
treatment solution
hollow body
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German (de)
French (fr)
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EP2215285A1 (en
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Maximilian SCHÖNHERR
Jerzy-Tadeusz Wawrzyniak
Eva Wiedemann
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Henkel AG and Co KGaA
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Henkel AG and Co KGaA
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    • 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
    • C23C22/05—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 using aqueous solutions
    • C23C22/06—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 using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/34—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
    • C23C22/36—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
    • C23C22/361—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing titanium, zirconium or hafnium compounds
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/20—Pretreatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4935—Heat exchanger or boiler making
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]

Definitions

  • the present invention relates to a process for the corrosion-protective pretreatment of metallic components, which at least partially comprise metallic iron surfaces, with a chromium-free aqueous treatment solution containing fluorocomplexes of zirconium and / or titanium and phosphate ions in a specific ratio range to each other, and a metallic component, which has been pretreated accordingly, and its use for the application of further anti-corrosive coatings and / or paint systems.
  • the method is particularly suitable as a pretreatment for an electrodeposition coating of metallic components, which are in the form of non-closed hollow bodies.
  • the present invention therefore also relates to a process for coating a non-closed metallic hollow body, which comprises both the pretreatment with the chromium-free aqueous treatment solution and a subsequent electrodeposition coating, and a metallic hollow body, which is coated according to the inventive method, and its use for the production of radiators.
  • the passivation of metallic materials is ensured primarily by the zinc or iron phosphating.
  • zinc or iron phosphating mostly crystalline inorganic coatings are produced on the metallic base material, which have a layer thickness of several micrometers and, due to their surface topography, have excellent adhesion to organic cover layers, especially to coating systems applied in the electrocoating process.
  • non-film-forming iron phosphating the conversion becomes the metal surface is typically made in a phosphoric acid medium also in the presence of accelerators and wetting agents at elevated bath temperature.
  • Such iron phosphate layers rarely have layer weights of more than 1 g / m 2 and, in contrast to phosphations with high layer weights, are amorphous.
  • the classical phosphating is a multi-step process consisting of a cleaning step to degrease the component, an activation process and ultimately the actual phosphating, wherein for decoupling the process baths in continuous operation rinsing steps are installed.
  • a rinsing process is obligatory, at least after the cleaning step, so that the phosphating is composed of at least four individual processes which have to be monitored and controlled in terms of process technology in individual baths.
  • Additional alternative methods for standard phosphating which provide coating weights of significantly more than 1 g / m 2 , are, in addition to the non-layering iron phosphating, conversion treatments of the metallic surfaces to form purely amorphous, inorganic passive layers with much lower coating weights of the order of magnitude less as 200 mg / m 2 .
  • Any pretreatment processes that produce such "non-film-forming" (non-crystalline) phosphating and / or metal surface conversion have the advantage of rendering surface activation unnecessary and can thus be saved in the process chain of pretreatment.
  • Another advantage over the layer-forming zinc phosphating is the reduction of phosphate sludge in the phosphating baths.
  • the DE 1933013 also discloses phosphate-free treatment baths with a pH above 3.5, in addition to complex fluorides of boron, titanium or zirconium in amounts of 0.1 to 15 g / l, based on the metals, in addition 0.5 to 30 g / l Contain oxidizing agent, in particular sodium m-nitrobenzenesulfonate.
  • oxidizing agent sodium m-nitrobenzenesulfonate comes according to the teaching of DE 1933013 the function to vary the treatment time of the metal surfaces in a particularly large extent.
  • the disclosed WO 03/002781 Pretreatment solutions containing not only phosphoric acid but also fluorocomplexes of zirconium and / or titanium and a homo- or copolymer of vinylpyrrolidone.
  • Such a pretreatment solution provides low mass mixed amorphous mixed organic / inorganic passivations which may be provided with an electrodeposition paint.
  • DE 2715292 discloses treatment baths for chromium-free pretreatment of aluminum cans containing at least 10 ppm of titanium and / or zirconium, between 10 and 1000 ppm of phosphate and a sufficient amount of fluoride to form complex fluorides of the existing titanium and / or zirconium, but at least 13 ppm, and pH Values between 1.5 and 4.
  • the WO 2009/045872 discloses, as a post-published prior art under Art. 54 (3) EPC, methods for anticorrosive treatment of iron surfaces comprising aqueous compositions having a pH in the range of 4 to 5.5, containing essentially one metal compound selected from Group IIIB and Group IIIB elements or IVB and phosphate ions wherein the weight ratio of metal compounds to phosphate ions is at least 2: 1, contacted with the iron surfaces and then coated with a film-forming resin-containing agent.
  • the WO 2009/045872 The embodiments in particular those methods for pretreatment in the context of the present invention, in which steel sheets first cleaned with an alkaline cleaner, then rinsed twice with city water, then with a bath, which is composed at a pH of 5 so that about 10 ppm Iron ions containing either 80 ppm zirconium and 55 ppm phosphate ions or 150 ppm zirconium and 100 ppm phosphate ions, treated and then rinsed with city water.
  • the DE 10 2005 059314 A1 discloses a conversion treatment for steel surfaces which are electrocoated.
  • the one used for this aqueous conversion solution has a pH of 2.5 to 5 and contains 10-500 ppm of Ti or Zr as Hexafluorokomplex.
  • the solution may contain 10 to 500 ppm of phosphate and 50 to 500 ppm of silica having an average particle size of less than 1 ⁇ m and 10 to 1000 ppm of aromatic hydroxycarboxylic acids and 500 to 2000 ppm of nitrobenzenesulfonic acid.
  • the WO 03/100130 A discloses a conversion process for steel surfaces which are electrocoated.
  • the conversion solutions include phosphate, a Group IVB metal compound, and an accelerator, which may be selected from nitrobenzenesulfonic acid.
  • the US-A-4017335 discloses a method for phosphating pretreatment of iron surfaces prior to subsequent application of an organic coating.
  • the concentrates for use in such a process may contain, in addition to phosphate, also fluoro acids of the elements Zr and Ti, a surfactant and an accelerator which may be nitrobenzenesulfonic acid.
  • the object of the present invention is therefore to provide a conversion treatment of metallic components consisting at least partially of iron, which compared to the non-layer-forming treatment methods known in the prior art at least comparable or improved results in terms of corrosion protection and electrodeposition paint consumption provides, without, however, having to resort to the complex and energy-intensive process steps of the layer-forming phosphating.
  • the alternative method is to provide a corrosion-protected metallic surface, in particular iron surface, in as few and easily controllable process steps as possible and, on the other hand, to be as resource-efficient as possible, avoiding residues which are difficult to work up, for example phosphate sludges.
  • such an alternative method must ensure the subsequent electrocoating of the treated metallic component, preferably in the form of a non-closed hollow body, with an optimal Lackumgriff generally the lowest possible paint consumption is sought.
  • the metallic component is preferably made entirely of iron and / or an iron alloy containing more than 50 at.% Of iron or surfaces whose iron content is greater than 50 at.%.
  • the treatment solution does not require any additions of chromium compounds and is therefore chromium-free for ecological reasons and to ensure a high level of occupational safety.
  • ions of chromium in a low concentration enter the pretreatment solution from the container material or from the surfaces to be treated, for example steel alloys.
  • concentration of chromium in the ready-to-use processing solution is not higher than about 10 ppm, preferably not higher than 1 ppm.
  • the pH of the treatment solution can be arbitrarily adjusted by adding dilute nitric acid or ammoniacal solution in the specified range.
  • the pH of the treatment solution is particularly preferably below 5.5, in particular below 5.0.
  • the performance of the pretreatment with regard to corrosion resistance of the treated components and the throw-over behavior in a subsequent electrodeposition coating can be adjusted.
  • excessively high ratios of zirconium and / or titanium to the phosphate present in the treatment solution as well as excessively low relative zirconium and / or titanium contents have a significantly negative effect on the throwing behavior.
  • An optimum result, that is to say maximum permeation in the paint deposition, is achieved if the molar ratio of zirconium and / or titanium to phosphate ions is set to not less than 1: 1.
  • zirconium compounds in the different embodiments of the present invention gives technically better results than the use of titanium compounds and is therefore preferred.
  • complex fluoro acids or their salts can be used.
  • treatment solutions which contain as component (i) at least 150 ppm, preferably at least 200 ppm, but not more than 350 ppm, preferably not more than 300 ppm of zirconium in the form of a fluorocomplex.
  • the phosphate content of the treatment solution according to the invention is extremely low in comparison with zinc or iron phosphating baths described in the prior art.
  • a low concentration of phosphate ions of at least 10 ppm in combination with the fluorocomplexes of zirconium and or titanium leads to the formation of a thin amorphous zirconium and / or titanium phosphate layer and thus to the desired passivation of the metal surface, in particular the iron surface.
  • a homogeneous passivation takes place already at phosphate contents of preferably 30 ppm, more preferably at least 60 ppm.
  • the phosphate content should not exceed 1000 ppm and preferably not more than 180 ppm, particularly preferably not more than 120 ppm phosphate ions.
  • accelerators known from zinc and iron phosphating promote the formation of a homogeneous passivation.
  • Such accelerators are oxidizing agents that perform the task of a "hydrogen scavenger" in the phosphating process by eliminating the hydrogen produced by the acid attack on the metallic surface oxidize directly and thereby reduce itself.
  • the inhibition of massive hydrogen evolution on the material surface facilitates the formation of the crystalline phosphate layer with several micrometers layer thickness during the layer-forming phosphating.
  • the accelerators known in the prior art are also able to support the homogeneous formation of an amorphous passive layer based on zirconium and / or titanium phosphate, which comprises only a few nanometers.
  • the activity of the accelerators in the treatment bath is to be set much lower than is the case, for example, in zinc phosphating, so that typical oxidizing agents have to be used in amounts of not more than 1000 ppm, but at least 10 ppm must be present in the treatment solution promote zirconium- and / or titanium-based passivation of the ferrous metal surface.
  • Typical representatives of the oxidizing agents are chlorate ions, nitrite ions, nitroguanidine, N-methylmorpholine N-oxide, m-nitrobenzoate ions, p-nitrophenol, m-nitrobenzenesulfonate ions, hydrogen peroxide in free or bound form, hydroxylamine in free or bound form, reducing Sugar.
  • the m-nitrobenzenesulfonate as the accelerator at the contents of not less than 20 ppm, preferably not less than 50 ppm and not more than 500 ppm, preferably not more than 300 ppm, significantly improved passivation properties of the treatment solution are achieved.
  • a further improvement of the passive layer properties and the adhesion to subsequently applied lacquer layers results when adding particulate inorganic, water-insoluble compounds of the elements silicon, aluminum, zinc, titanium, zirconium, iron, calcium and / or magnesium, the content of these compounds in the treatment solution based on the element is at least 10 ppm, but should not exceed 200 ppm in order not to destabilize the treatment solution by agglomeration and sedimentation of the particulate components.
  • the oxidic compounds of said elements used in nanoparticulate form.
  • German patent application DE 100 05 113 based on the finding that homopolymers or copolymers of vinylpyrrolidone have an excellent corrosion protection effect.
  • polymers having hydroxyl and / or carboxyl functionalities are often added in substantial amounts (> 1 g / l) to the passivation baths in order to act as binders in the inorganic passive layer to act as further binders to subsequently applied organic coatings.
  • the addition of other polymers significantly increases the process cost, since depending on the transfer ("drag over") of the polymeric components from the pretreatment solution in the dip coating the stability of the dip bath or the quality of the paint coating itself can be adversely affected.
  • the process of the present invention should be adjusted to phosphate ion ratios with respect to molar ratios of zirconium and / or titanium to reduce the rinse time and rinse water level be that of a polymer addition can be waived entirely. Therefore, the present invention relates only to those methods in which the amount of organic polymers in the processing solution is not larger than 1 ppm.
  • the inventive method requires no further inorganic additives selected from oxo anions of vanadium, tungsten and / or molybdenum, in order to produce a sufficient passivation of the metal surface, in particular iron surface.
  • oxoanions in particular vanadates and molybdates
  • small amounts of these oxoanions, in particular vanadates and molybdates may be present as an additional constituent in the treatment solution in the process according to the invention in order to detect defects in the zirconium- and / or titanium-based phosphate layer already during the passivation heal. Because of Process economics, however, the proportion of these compounds in the treatment solution of the method according to the invention based on the respective element is less than 50 ppm, preferably less than 10 ppm.
  • the treatment solution may additionally contain chelating substances.
  • chelating substances in particular those based on ⁇ -hydroxycarboxylic acids, stabilizes the pickling rate in the treatment bath for a longer service life of a bath, so that largely independent of the content of the metal ions, the by pickling the metal surface into the Bad, constant coating conditions of the zirconium and / or titanium-based phosphate layer result.
  • the sludge formation consisting of sparingly soluble metal hydroxides can be significantly minimized.
  • the chelating substances are added as an additive to the treatment solution in the process according to the invention selected from ⁇ -hydroxycarboxylic acids, more preferably selected from polyhydroxy acids having not more than 8 carbon atoms, in particular gluconic acid is preferred.
  • the content of chelating substances in the treatment solution of the process according to the invention is preferably at least 0.01% by weight, more preferably at least 0.05% by weight, but preferably not more than 2% by weight, more preferably not more than 1 wt .-%.
  • the metallic component to be treated in the process according to the invention is optionally previously freed of superficial impurities, in particular lubricants and / or corrosion protection oils, in a cleaning step. If such a cleaning is omitted, a passivation homogeneously formed over the entire metal surface of the component can not be achieved in the method according to the invention.
  • the acidic treatment solution of the process according to the invention may additionally contain at least one surface-active substance, so that the effective Cleaning the metal surfaces of the component and their passivation associated with each other.
  • the use of surface-active substances in passivating pretreatment solutions is not self-evident and thus surprising in the process according to the invention.
  • nonionic surfactants in phosphate-free treatment baths according to the DE 1933013 (Bonderite NT ® ) no adequate passivation of the metal surface.
  • surface-active substances it is possible in principle to use all customary surfactants, preferably nonionic surfactants, which are stable in the treatment solution of the process according to the invention and have a low critical micelle formation concentration below 10 -3 mol / l, preferably below 10 -4 mol / l.
  • the passivating pretreatment process according to the invention is preferably carried out at bath temperatures of the treatment solution of not more than 40.degree. If the pretreatment solution additionally contains surface-active substances, then the bath temperature for sufficient cleaning of the metal surfaces of the component to be treated is preferably at least 30 ° C., wherein higher bath temperatures than 80 ° C. are not required and have a negative effect on the energy efficiency of the process.
  • the metal surfaces may be brought into contact with the pretreatment solution by either dipping or spraying.
  • the present invention also encompasses a process for the corrosion-protective coating of non-closed metallic hollow bodies, which at least partially comprise metallic iron surfaces, wherein the above-described inventive process for corrosion-protective pretreatment is followed by an electrodeposition coating with or without intermediate rinsing step.
  • the resulting after the pretreatment according to the invention amorphous and extremely thin zirconium and / or titanium-based phosphate passivation after Electrocoating an acceptable corrosion resistance and paint adhesion compared to electrocoated crystalline phosphate coatings.
  • such non-closed metallic hollow bodies are to be at least partially coated with iron surfaces in which the ratio of the inner surface area of the non-closed hollow body to the opening area of the same is not less than 5, that is, for example, at least cube-shaped.
  • the Umgriff so the deposition of the dip paint on the opposite sides of the counter electrode electrode or on the inner regions of the metallic hollow body, which are almost field-free due to their Faraday shielding at the beginning of the deposition and therefore only accessible via the resistance structure of the depositing paint layer for film formation is determined decisively by the passivating pretreatment according to the invention and can therefore also be used as a characterizing feature of the pretreatment according to the invention or of the coating according to the invention.
  • the process-specific limitation of the layer thickness of the electrodeposition paint is crucial for the encirclement of the paint, as with the same amount of charge, but lesser limited or maximum film thickness, inevitably a better throwing takes place.
  • a specific layer thickness limitation as the ratio of the layer thickness of Electrocoating paint on the outer surface of a hollow body according to the invention coated to the thickness of the electrodeposition paint after identical, but only electrocoating without prior pretreatment on the identical outer surface of an identical untreated, but cleaned and degreased hollow body. This should not be greater than 0.95, preferably not greater than 0.9, and more preferably not greater than 0.8 according to the present invention.
  • the method according to the invention for coating a metallic hollow body can be carried out in such a way that a rinsing step takes place between the method steps of the pretreatment according to the invention and the electrocoating step, preferably with deionized water or city water.
  • no drying of the metallic hollow body takes place after the pretreatment according to the invention and before the electrocoating process step.
  • the present invention likewise relates to the metallic components and non-closed metallic hollow bodies treated directly with the method according to the invention for the pretreatment and coating, wherein the metallic components and hollow bodies to be treated at least partially have metallic iron surfaces.
  • the present invention encompasses the use of a metallic component whose entire surface, which consists at least partly of metallic iron surfaces, has been pretreated with the chromium-free aqueous treatment solution in accordance with the method according to the invention for the application of further corrosion-protective coatings and / or organic coating systems.
  • the present invention comprises the use of a non-closed metallic hollow body whose entire surface, which at least partially consists of metallic iron surfaces, according to the inventive method first pretreated with the chromium-free aqueous treatment solution and then electrocoated with or without intervening rinsing step, for the production of radiators.
  • Embodiments according to the invention and comparative examples for the pretreatment of steel sheets (CRS: cold rolled steel) including their subsequent electrodeposition coating are mentioned below.
  • CRS sheets are treated by immersion for 5 min at 50 ° C in an aqueous solution composed of 3 wt .-% Ridoline 1562 ® and 0.3 wt .-% Ridosol 1270 ® while stirring the cleaning solution.
  • CRS sheets are first cleaned in the immersion process according to the comparative example "alkaline cleaning", after which the cleaned sheet is rinsed for 1 minute under running demineralized water (k ⁇ 1 ⁇ Scm -1 ). Subsequently, the treatment with Bonderite NT-1 ® (Henkel KGaA) of a zirconium-containing, but phosphate-free aqueous solution is carried out by immersion for 1 min at 20 ° C. The thus pretreated sheet is then rinsed for 1 min under running demineralised water (k ⁇ 1 ⁇ Scm -1 ).
  • Bonderite NT-1 ® Heenkel KGaA
  • CRS sheets are first cleaned in the immersion process according to the comparative example "alkaline cleaning", after which the cleaned sheet is rinsed for 1 minute under running demineralized water (k ⁇ 1 ⁇ Scm -1 ).
  • the treatment with the commercial product Granodine 958 ® (Messrs. Henkel KGaA) according to the instructions Subsequently, the dipping method. This treatment includes an activation step before the actual phosphating.
  • the thus pretreated sheet is then rinsed for 1 min under running demineralized water ( ⁇ ⁇ 1 ⁇ Scm -1 ).
  • CRS sheets are first cleaned in the immersion process according to the comparative example "alkaline cleaning", after which the cleaned sheet for 1 min rinsed with running demineralised water (k ⁇ 1 ⁇ Scm -1 ). Subsequently, in the spraying process, the treatment is carried out with an aqueous solution according to the invention composed of 300 ppm Zr as H 2 ZrF 6 , 100 ppm PO 4 as H 3 PO 4 , 100 ppm Sodium m-nitrobenzenesulfonate (m-NBS) and 3000 ppm Ridosol 2000 ® (cleaner Fa. Henkel KGaA) for 2 min at 50 ° C, wherein the pH is adjusted to pH 4.5 with ammoniacal solution. The thus pretreated sheet is then rinsed for 1 min under running demineralized water (k ⁇ 1 ⁇ Scm -1 ).
  • an aqueous solution according to the invention composed of 300 ppm Zr as H 2 ZrF 6 , 100 ppm PO
  • All pretreated sheets are then coated with a cathodic immersion coating Cathogard 500 from BASF and baked at 180 ° C for 30 min.
  • the average coating thickness is determined by means of the Coating Thickness Gauge PosiTector 6000 (DeFelsko Ltd., Canada) by multiple measurements at different points on the anode-facing side of the sheet.
  • the layer thickness of the zinc phosphate layer is first determined by multiple measurement before the electrodeposition coating and subtracted from the determined layer thickness after painting.
  • the pretreatment according to the invention has the lowest layer thickness compared to the "non-layer-forming" pretreatments with identical electrodeposition coating time. Only the layer-forming phosphated CRS sheet has an even lower coating thickness after the electro-dip coating.
  • the infiltration values are so similar and even better than those that adapt to the corrosive infiltration after an iron phosphating after 504 hours and typically be 1.5 mm, and slightly larger than after pretreatment with Bonderite NT-1 ®, the infiltration levels of 0.9 mm.

Description

Die vorliegende Erfindung betrifft ein Verfahren zur korrosionsschützenden Vorbehandlung von metallischen Bauteilen, die zumindest teilweise metallische Oberflächen aus Eisen aufweisen, mit einer chromfreien wässrigen Behandlungslösung, die Fluorokomplexe von Zirconium und/oder Titan sowie Phosphationen in einem spezifischen Verhältnisbereich zueinander enthält, sowie ein metallisches Bauteil, das entsprechend vorbehandelt ist, und dessen Verwendung für die Applikation weiterer korrosionsschützender Beschichtungen und/oder Lacksysteme. Das Verfahren eignet sich insbesondere als Vorbehandlung für eine Elektrotauchlackierung von metallischen Bauteilen, die in Form von nicht-geschlossenen Hohlkörpern vorliegen. Gegenstand der vorliegenden Erfindung ist daher ebenso ein Verfahren zur Beschichtung eines nicht-geschlossenen metallischen Hohlkörpers, welches sowohl die Vorbehandlung mit der chromfreien wässrigen Behandlungslösung als auch eine nachfolgende Elektrotauchlackierung umfasst, sowie ein metallischer Hohlkörper, der entsprechend des erfindungsgemäßen Verfahrens beschichtet ist, und dessen Verwendung für die Herstellung von Radiatoren.The present invention relates to a process for the corrosion-protective pretreatment of metallic components, which at least partially comprise metallic iron surfaces, with a chromium-free aqueous treatment solution containing fluorocomplexes of zirconium and / or titanium and phosphate ions in a specific ratio range to each other, and a metallic component, which has been pretreated accordingly, and its use for the application of further anti-corrosive coatings and / or paint systems. The method is particularly suitable as a pretreatment for an electrodeposition coating of metallic components, which are in the form of non-closed hollow bodies. The present invention therefore also relates to a process for coating a non-closed metallic hollow body, which comprises both the pretreatment with the chromium-free aqueous treatment solution and a subsequent electrodeposition coating, and a metallic hollow body, which is coated according to the inventive method, and its use for the production of radiators.

Die Passivierung von metallischen Werkstoffen, insbesondere von Eisen und Eisenstählen, wird vornehmlich über die Zink- oder Eisenphosphatierung gewährleistet. So werden bei der Zink- oder Eisenphosphatierung zumeist kristalline anorganische Überzüge auf dem metallischen Basismaterial erzeugt, die eine Schichtdicke von mehreren Mikrometern aufweisen und aufgrund ihrer Oberflächentopographie eine hervorragende Haftung zu organischen Deckschichten, speziell zu im Elektrotauchverfahren aufgebrachten Lacksystemen, besitzen. Bei der nichtschichtbildenden Eisenphosphatierung wird die Konversion der Metalloberfläche typischerweise in einem phosphorsauren Medium ebenfalls in Gegenwart von Beschleunigern und Netzmitteln bei erhöhter Badtemperatur vorgenommen. Derartige Eisenphosphatschichten weisen selten Schichtgewichte von mehr als 1 g/m2 auf und sind im Gegensatz zu Phosphatierungen mit hohen Schichtgewichten amorph. Üblicherweise stellt die klassische Phosphatierung ein Mehrschritt-Verfahren bestehend aus einem Reinigungsschritt zur Entfettung des Bauteils, einem Aktivierungsprozess und letztendlich der eigentlichen Phosphatierung dar, wobei zur Entkopplung der Prozessbäder im kontinuierlichen Betrieb Spülschritte eingebaut sind. Ein derartiger Spülvorgang ist zumindest nach dem Reinigungsschritt obligat, so dass die Phosphatierung sich aus mindestens vier Einzelprozessen zusammensetzt, die verfahrenstechnisch in Einzelbädern überwacht und gesteuert werden müssen. Diese hohen verfahrenstechnischen Anforderungen und die damit verbundene Komplexität eines Phosphatierbetriebes stellen zuweilen ein Hindernis für die Einführung einer derartigen Passivierung der Bauteile in Low-Cost-Anwendungen jenseits der automobilen Fertigung dar. Ein weiterer Nachteil technischer Natur ist die Aufarbeitung von Reststoffen, wie von mit Schwermetallen belasteten Phosphatschlämmen, die bei den hohen Phosphat-Gehalten im passivierenden Tauchbad nicht vermeidbar sind und nur unter erneutem Energie- und Stoffumsatz aufgearbeitet werden können. Nicht zuletzt die erhöhten Badtemperaturen machen die klassische Phosphatierung damit insgesamt zu einem Verfahren mit hohem Energieaufwand und einem enormen Bedarf an Rückgewinnungsmaßnahmen.The passivation of metallic materials, in particular of iron and iron steels, is ensured primarily by the zinc or iron phosphating. Thus, in the case of zinc or iron phosphating, mostly crystalline inorganic coatings are produced on the metallic base material, which have a layer thickness of several micrometers and, due to their surface topography, have excellent adhesion to organic cover layers, especially to coating systems applied in the electrocoating process. In non-film-forming iron phosphating, the conversion becomes the metal surface is typically made in a phosphoric acid medium also in the presence of accelerators and wetting agents at elevated bath temperature. Such iron phosphate layers rarely have layer weights of more than 1 g / m 2 and, in contrast to phosphations with high layer weights, are amorphous. Typically, the classical phosphating is a multi-step process consisting of a cleaning step to degrease the component, an activation process and ultimately the actual phosphating, wherein for decoupling the process baths in continuous operation rinsing steps are installed. Such a rinsing process is obligatory, at least after the cleaning step, so that the phosphating is composed of at least four individual processes which have to be monitored and controlled in terms of process technology in individual baths. These high procedural requirements and the associated complexity of a Phosphatierbetriebes sometimes present an obstacle to the introduction of such a passivation of the components in low-cost applications beyond the automotive manufacturing. Another disadvantage of a technical nature is the processing of residues, such as heavy metals loaded phosphate sludge, which are unavoidable at the high phosphate levels in the passivating dip and can be worked up only with renewed energy and turnover. Not least, the increased bath temperatures make the classic phosphating a process with a high energy consumption and an enormous need for recovery measures.

Zusätzliche Alternativverfahren zur Standard-Phosphatierung, die Schichtgewichte von deutlich mehr als 1 g/m2 liefert, sind neben der nicht-schichtbildenden Eisenphosphatierung Konversionsbehandlungen der metallischen Oberflächen unter Ausbildung von rein amorphen, anorganischen Passivschichten mit weit niedrigeren Schichtgewichten in der Größenordnung von zum Teil weniger als 200 mg/m2.
Sämtliche Verfahren zur Vorbehandlung, die eine solche "nicht-schichtbildende" (nicht-kristalline) Phosphatierung und/oder Konversion der Metalloberfläche herbeiführen, haben den Vorteil, dass eine Aktivierung der Oberfläche überflüssig wird und so in der Prozesskette der Vorbehandlung eingespart werden kann. Ein weiterer Vorteil gegenüber der schichtbildenden Zinkphosphatierung ist die Verringerung von Phosphatschlämmen in den Phosphatierbädern.Additional alternative methods for standard phosphating, which provide coating weights of significantly more than 1 g / m 2 , are, in addition to the non-layering iron phosphating, conversion treatments of the metallic surfaces to form purely amorphous, inorganic passive layers with much lower coating weights of the order of magnitude less as 200 mg / m 2 .
Any pretreatment processes that produce such "non-film-forming" (non-crystalline) phosphating and / or metal surface conversion have the advantage of rendering surface activation unnecessary and can thus be saved in the process chain of pretreatment. Another advantage over the layer-forming zinc phosphating is the reduction of phosphate sludge in the phosphating baths.

Beispielsweise lehren die US 5,356,490 und die WO 04/063414 phosphatfreie und chromfreie wässrige Behandlungslösungen enthaltend Zirconium- und/oder Titanverbindungen, die im sauren Medium aufgrund des Beizangriffes der behandelten metallischen Oberflächen als so genannte passivierende Konversionsschicht auf dem metallischen Bauteil abgeschieden werden. Beide Schriften lehren, dass dispergierte wasserunlösliche anorganische Verbindungen zusätzlich enthalten sein müssen, um den gewünschten Effekt hinsichtlich Korrosionsschutz und Lackhaftung zu erzielen, wobei die WO 04/063414 explizit das Vorhandensein von säurestabilen, nanodispergierten Verbindungen auf der Basis von Silika fordert und im Gegensatz zur US 5,356,490 ohne den Zusatz von organischen Polymeren auskommt.For example, the teach US 5,356,490 and the WO 04/063414 Phosphate-free and chromium-free aqueous treatment solutions containing zirconium and / or titanium compounds which are deposited in the acidic medium due to the pickling attack of the treated metallic surfaces as a so-called passivating conversion layer on the metallic component. Both documents teach that dispersed water-insoluble inorganic compounds must be additionally present in order to achieve the desired effect with regard to corrosion protection and paint adhesion, wherein the WO 04/063414 explicitly requires the presence of acid-stable, nanodispersed compounds based on silica and in contrast to US 5,356,490 works without the addition of organic polymers.

Die DE 1933013 offenbart ebenfalls phosphatfreie Behandlungsbäder mit einem pH-Wert oberhalb 3,5, die neben komplexen Fluoriden des Bors, Titans oder Zirconiums in Mengen von 0,1 bis 15 g/l, bezogen auf die Metalle, zusätzlich 0,5 bis 30 g/l Oxidationsmittel, insbesondere Natrium-m-nitrobenzolsulfonat enthalten. Dem Oxidationsmittel Natrium-m-nitrobenzolsulfonat kommt gemäß der Lehre der DE 1933013 die Funktion zu, die Behandlungsdauer der Metalloberflächen in besonders großem Umfang zu variieren.The DE 1933013 also discloses phosphate-free treatment baths with a pH above 3.5, in addition to complex fluorides of boron, titanium or zirconium in amounts of 0.1 to 15 g / l, based on the metals, in addition 0.5 to 30 g / l Contain oxidizing agent, in particular sodium m-nitrobenzenesulfonate. The oxidizing agent sodium m-nitrobenzenesulfonate comes according to the teaching of DE 1933013 the function to vary the treatment time of the metal surfaces in a particularly large extent.

Demgegenüber offenbart die WO 03/002781 Vorbehandlungslösungen enthaltend neben Phosphorsäure auch Fluorokomplexe von Zirconium- und/oder Titan und ein Homo- oder Copolymer von Vinylpyrrolidon. Eine solche Vorbehandlungslösung liefert amorphe gemischt organisch/anorganische Passivierungen mit niedrigem Schichtgewicht, die mit einem Elektrotauchlack versehen werden können.In contrast, the disclosed WO 03/002781 Pretreatment solutions containing not only phosphoric acid but also fluorocomplexes of zirconium and / or titanium and a homo- or copolymer of vinylpyrrolidone. Such a pretreatment solution provides low mass mixed amorphous mixed organic / inorganic passivations which may be provided with an electrodeposition paint.

DE 2715292 offenbart Behandlungsbäder für die chromfreie Vorbehandlung von Aluminiumdosen, die mindestens 10 ppm Titan und/oder Zirconium, zwischen 10 und 1000 ppm Phosphat und eine zur Bildung komplexer Fluoride des vorhandenen Titans und/oder Zirconiums ausreichenden Menge Fluorid, mindestens jedoch 13 ppm, enthalten und pH-Werte zwischen 1,5 und 4 aufweisen. DE 2715292 discloses treatment baths for chromium-free pretreatment of aluminum cans containing at least 10 ppm of titanium and / or zirconium, between 10 and 1000 ppm of phosphate and a sufficient amount of fluoride to form complex fluorides of the existing titanium and / or zirconium, but at least 13 ppm, and pH Values between 1.5 and 4.

Aus der Offenlegungsschrift US 2007/0068602 geht eine passivierende Vorbehandlungslösung hervor, die neben Fluorokomplexen von Zirconium und Phosphat-Anionen auch Oxoanionen von Vanadium enthält, deren jeweiligen Gehalte in einem vorgegebenen Verhältnisbereich zueinander stehen müssen, um einen effektiven Korrosionsschutz zu erzielen.From the publication US 2007/0068602 shows a passivating pretreatment solution which, in addition to fluorocomplexes of zirconium and phosphate anions, also contains oxo anions of vanadium, the respective contents of which must be within a given ratio range in order to achieve effective corrosion protection.

Die WO 2009/045872 offenbart als nachveröffentlichter Stand der Technik gemäß Art. 54(3) EPÜ Verfahren zur korrosionsschützenden Behandlung von Eisenoberflächen, bei dem wässrige Zusammensetzungen mit einem pH-Wert im Bereich von 4 bis 5,5 enthaltend im Wesentlichen eine Metallverbindung ausgewählt aus Elementen der Gruppen IIIB und/oder IVB und Phosphationen, wobei das Gewichtsverhältnis von Metallverbindungen zu Phosphationen zumindest 2 : 1 beträgt, mit den Eisenoberflächen in Kontakt gebracht und selbige anschließend mit einem ein filmbildendes Harz enthaltendes Mittel beschichtet werden. Insbesondere offenbart die WO 2009/045872 den Ausführungsbeispielen insbesondere solche Verfahren zur Vorbehandlung im Sinne der vorliegenden Erfindung, in denen Stahlbleche zunächst mit einem alkalischen Reiniger gereinigt, danach zweimal mit Stadtwasser gespült, sodann mit einem Bad, das bei einem pH-Wert von 5 so zusammengesetzt ist, dass neben 10 ppm Eisen-Ionen entweder 80 ppm Zirconium und 55 ppm Phosphationen oder 150 ppm Zirconium und 100 ppm Phosphationen enthalten sind, behandelt und anschließend mit Stadtwasser gespült werden.The WO 2009/045872 discloses, as a post-published prior art under Art. 54 (3) EPC, methods for anticorrosive treatment of iron surfaces comprising aqueous compositions having a pH in the range of 4 to 5.5, containing essentially one metal compound selected from Group IIIB and Group IIIB elements or IVB and phosphate ions wherein the weight ratio of metal compounds to phosphate ions is at least 2: 1, contacted with the iron surfaces and then coated with a film-forming resin-containing agent. In particular, the WO 2009/045872 The embodiments in particular those methods for pretreatment in the context of the present invention, in which steel sheets first cleaned with an alkaline cleaner, then rinsed twice with city water, then with a bath, which is composed at a pH of 5 so that about 10 ppm Iron ions containing either 80 ppm zirconium and 55 ppm phosphate ions or 150 ppm zirconium and 100 ppm phosphate ions, treated and then rinsed with city water.

Die DE 10 2005 059314 A1 offenbart eine Konversionsbehandlung für Stahloberflächen, die elektrotauchlackiert werden. Die hierfür verwendete wässrige Konversionslösung hat einen pH-Wert von 2,5 bis 5 und enthält 10-500 ppm Ti oder Zr als Hexafluorokomplex. Weiterhin kann die Lösung 10 - 500 ppm Phosphat und 50 - 500 ppm Kieselsäure mit einer mittleren Teilchengröße von weniger als 1 µm sowie 10 - 1000 ppm an aromatischen Hydroxycarbonsäuren und 500 - 2000 ppm Nitrobenzolsulfonsäure enthalten.The DE 10 2005 059314 A1 discloses a conversion treatment for steel surfaces which are electrocoated. The one used for this aqueous conversion solution has a pH of 2.5 to 5 and contains 10-500 ppm of Ti or Zr as Hexafluorokomplex. Furthermore, the solution may contain 10 to 500 ppm of phosphate and 50 to 500 ppm of silica having an average particle size of less than 1 μm and 10 to 1000 ppm of aromatic hydroxycarboxylic acids and 500 to 2000 ppm of nitrobenzenesulfonic acid.

Die WO 03/100130 A offenbart ein Konversionsverfahren für Stahloberflächen, die elektrotauchlackiert werden. Die Konversionslösungen enthalten Phosphat, eine Verbindung eines Metalls der Gruppe IVB und einen Beschleuniger, der ausgewählt sein kann aus Nitrobenzolsulfonsäure.The WO 03/100130 A discloses a conversion process for steel surfaces which are electrocoated. The conversion solutions include phosphate, a Group IVB metal compound, and an accelerator, which may be selected from nitrobenzenesulfonic acid.

Die US-A-4017335 offenbart eine Methode zur phosphatierenden Vorbehandlung von Eisenoberflächen vor einer nachfolgenden Aufbringung einer organischen Beschichtung. Die Konzentrate zur Anwendung in einem solchen Verfahren können neben Phosphat, auch Fluorosäuren der Elemente Zr und Ti, ein Tensid und einen Beschleuniger, der Nitrobenzolsulfonsäure sein kann, enthalten.The US-A-4017335 discloses a method for phosphating pretreatment of iron surfaces prior to subsequent application of an organic coating. The concentrates for use in such a process may contain, in addition to phosphate, also fluoro acids of the elements Zr and Ti, a surfactant and an accelerator which may be nitrobenzenesulfonic acid.

Dem Stand der Technik zur passivierenden Vorbehandlung mit Zusammensetzungen enthaltend Verbindungen von Zirconium- und/oder Titan und Phosphat kann jedoch keine Lehre entnommen werden, welche spezifischen Zusammensetzungen derartiger Vorbehandlungslösungen einen optimalen Korrosionsschutz bei optimaler Elektrotauchlackierbarkeit der amorphen Passivierungsschichten gewährleisten. Insbesondere ist für die Originalhersteller ein vergleichsweise geringer Lackverbrauch bei gutem Lackumgriff und gleicher Korrosionsbeständigkeit des beschichteten metallischen Bauteils von wirtschaftlicher Bedeutung.However, the prior art for passivating pretreatment with compositions comprising compounds of zirconium and / or titanium and phosphate can not be taught which specific compositions of such pretreatment solutions ensure optimum corrosion protection with optimum electrocoatability of the amorphous passivation layers. In particular, for the original manufacturer, a comparatively low paint consumption with good paint coverage and the same corrosion resistance of the coated metallic component is of economic importance.

Die Aufgabe der vorliegenden Erfindung besteht demnach darin, eine Konversionsbehandlung von metallischen Bauteilen bestehend zumindest teilweise aus Eisen bereitzustellen, die gegenüber den im Stand der Technik bekannten nicht-schichtbildenden Behandlungsmethoden zumindest vergleichbare oder verbesserte Resultate bezüglich Korrosionsschutz und Elektrotauchlackverbrauch liefert, ohne jedoch auf die aufwendigen und energieintensiven Prozessschritte der schichtbildenden Phosphatierung zurückgreifen zu müssen. Dabei soll das alternative Verfahren zum einen in möglichst wenigen und leicht zu kontrollierenden Prozessschritten eine korrosionsgeschützte metallische Oberfläche, insbesondere Eisenoberfläche, bereitstellen und zum anderen möglichst ressourcenschonend unter Vermeidung von schwer aufzuarbeitenden Reststoffen, beispielsweise Phosphatschlämmen, durchführbar sein. Darüber hinaus muss ein solches Alternativverfahren die nachträgliche Elektrotauchlackierung des behandelten metallischen Bauteils, vorzugsweise in Form eines nicht-geschlossenen Hohlkörpers, gewährleisten, wobei bei optimalem Lackumgriff grundsätzlich ein möglichst niedriger Lackverbrauch angestrebt wird.The object of the present invention is therefore to provide a conversion treatment of metallic components consisting at least partially of iron, which compared to the non-layer-forming treatment methods known in the prior art at least comparable or improved results in terms of corrosion protection and electrodeposition paint consumption provides, without, however, having to resort to the complex and energy-intensive process steps of the layer-forming phosphating. The alternative method is to provide a corrosion-protected metallic surface, in particular iron surface, in as few and easily controllable process steps as possible and, on the other hand, to be as resource-efficient as possible, avoiding residues which are difficult to work up, for example phosphate sludges. In addition, such an alternative method must ensure the subsequent electrocoating of the treated metallic component, preferably in the form of a non-closed hollow body, with an optimal Lackumgriff generally the lowest possible paint consumption is sought.

Diese Aufgabe wird gelöst durch ein Verfahren zur korrosionsschützenden Vorbehandlung metallischer Bauteile, die zumindest teilweise metallische Oberflächen aus Eisen aufweisen, wobei das Bauteil mit einer chromfreien wässrigen Behandlungslösung enthaltend

  1. (i) nicht weniger als 50 ppm und nicht mehr als 1000 ppm Zirconium und/oder Titan in Form ihrer Fluorokomplexe,
  2. (ii) nicht weniger als 10 ppm und nicht mehr als 1000 ppm Phosphationen, wobei das molare Verhältnis von Zirconium und/oder Titan zu Phosphationen nicht größer als 10 : 1 und nicht kleiner als 1 : 1 ist,
  3. (iii) weniger als 50 ppm an Oxoanionen von Vanadium, Wolfram und/oder Molybdän, sowie
  4. (iv) nicht mehr als 1 ppm an organischen Polymeren,
bei einem pH-Wert von nicht weniger als 3,5 und nicht größer als 6,0 in Kontakt gebracht wird, wobei solche Verfahren ausgenommen sind, in denen Stahlbleche zunächst mit einem alkalischen Reiniger gereinigt, danach zweimal mit Stadtwasser gespült, sodann mit einem Bad, das bei einem pH-Wert von 5 so zusammengesetzt ist, dass neben 10 ppm Eisen-Ionen entweder 80 ppm Zirconium und 55 ppm Phosphationen oder 150 ppm Zirconium und 100 ppm Phosphationen enthalten sind, behandelt und anschließend mit Stadtwasser gespült werden.This object is achieved by a method for corrosion-protective pretreatment of metallic components which at least partially comprise metallic iron surfaces, the component being provided with a chromium-free aqueous treatment solution
  1. (i) not less than 50 ppm and not more than 1000 ppm zirconium and / or titanium in the form of their fluoro complexes,
  2. (ii) not less than 10 ppm and not more than 1000 ppm of phosphate ions, wherein the molar ratio of zirconium and / or titanium to phosphate ions is not greater than 10: 1 and not less than 1: 1,
  3. (iii) less than 50 ppm of oxoanions of vanadium, tungsten and / or molybdenum, as well as
  4. (iv) not more than 1 ppm of organic polymers,
is contacted at a pH of not less than 3.5 and not greater than 6.0, except those methods in which steel sheets are first cleaned with an alkaline cleaner, then rinsed twice with city water, then with a bath which is composed at a pH of 5 to treat, in addition to 10 ppm iron ions, either 80 ppm zirconium and 55 ppm phosphate ions or 150 ppm zirconium and 100 ppm phosphate ions, and then rinse with city water.

Vorzugsweise besteht das metallische Bauteil dabei vollständig aus Eisen und/oder einer Eisenlegierung mit einem Gehalt von mehr als 50 At.-% an Eisen oder aus Oberflächen, deren Eisenanteil größer als 50 At.-% ist.In this case, the metallic component is preferably made entirely of iron and / or an iron alloy containing more than 50 at.% Of iron or surfaces whose iron content is greater than 50 at.%.

Die Behandlungslösung bedarf keiner Zusätze an Chrom-Verbindungen und ist daher aus ökologischen Gründen und zur Gewährleistung eines hohen Arbeitsschutzes chromfrei. Es ist jedoch nicht auszuschließen, dass aus dem Behältermaterial oder aus den zu behandelnden Oberflächen wie beispielsweise Stahllegierungen Ionen von Chrom in geringer Konzentration in die Vorbehandlungslösung gelangen. Jedoch wird in der Praxis erwartet, dass die Konzentration von Chrom in der anwendungsfertigen Behandlungslösung nicht höher als etwa 10 ppm, vorzugsweise nicht höher als 1 ppm ist.
Der pH-Wert der Behandlungslösung kann mittels der Zugabe von verdünnter Salpetersäure oder ammoniakalischer Lösung in dem angegebenen Bereich beliebig eingestellt werden. Besonders bevorzugt liegt der pH-Wert der Behandlungslösung jedoch unterhalb von 5,5, insbesondere unterhalb von 5,0.The treatment solution does not require any additions of chromium compounds and is therefore chromium-free for ecological reasons and to ensure a high level of occupational safety. However, it can not be ruled out that ions of chromium in a low concentration enter the pretreatment solution from the container material or from the surfaces to be treated, for example steel alloys. However, in practice, it is expected that the concentration of chromium in the ready-to-use processing solution is not higher than about 10 ppm, preferably not higher than 1 ppm.
The pH of the treatment solution can be arbitrarily adjusted by adding dilute nitric acid or ammoniacal solution in the specified range. However, the pH of the treatment solution is particularly preferably below 5.5, in particular below 5.0.

Über das molare Verhältnis von Zirconium und/oder Titan zum in der Behandlungslösung befindlichen Phosphat kann die Performance der Vorbehandlung hinsichtlich Korrosionsbeständigkeit der behandelten Bauteile und des Umgriffverhaltens bei einer sich anschließenden Elektrotauchlackierung abgestimmt werden. Überraschenderweise zeigt sich, dass sowohl zu hohe Verhältnisse von Zirconium und/oder Titan zum in der Behandlungslösung befindlichen Phosphat als auch zu niedrige relative Zirconium- und/oder Titan-Gehalte das Umgriffverhalten deutlich negativ beeinflussen. Ein optimales Ergebnis also ein maximaler Umgriff bei der Lackabscheidung wird dann erreicht, wenn das molare Verhältnis von Zirconium und/oder Titan zu Phosphationen nicht kleiner als 1 : 1 eingestellt wird. Bei einer Erhöhung des Verhältnisses zugunsten von Zirconium und/oder Titan auf Werte größer als 10 : 1 kann eine zirconium- und/oder titanbasierte Phosphatpassivierung offensichtlich nicht mehr effektiv vollzogen werden, da der Umgriff bei der nachträglichen Lackabscheidung deutlich abnimmt. Gleiches gilt auch für die korrosionsschützenden Eigenschaften der Vorbehandlung, die in den angegebenen bevorzugten Bereichen für die molaren Verhältnisse von Zirconium- und/oder Titan zu Phosphationen besonders ausgeprägt sind.By means of the molar ratio of zirconium and / or titanium to the phosphate present in the treatment solution, the performance of the pretreatment with regard to corrosion resistance of the treated components and the throw-over behavior in a subsequent electrodeposition coating can be adjusted. Surprisingly, it has been found that excessively high ratios of zirconium and / or titanium to the phosphate present in the treatment solution as well as excessively low relative zirconium and / or titanium contents have a significantly negative effect on the throwing behavior. An optimum result, that is to say maximum permeation in the paint deposition, is achieved if the molar ratio of zirconium and / or titanium to phosphate ions is set to not less than 1: 1. With an increase in the ratio in favor of zirconium and / or titanium to values greater than 10: 1, a zirconium- and / or titanium-based phosphate passivation can obviously no longer be effectively carried out, since the throwing off in the subsequent paint deposition decreases markedly. The same applies to the anti-corrosive properties of Pretreatment, which are particularly pronounced in the specified preferred ranges for the molar ratios of zirconium and / or titanium to phosphate ions.

Die Verwendung von Zirconiumverbindungen liefert bei den unterschiedlichen Ausführungsformen der vorliegenden Erfindung technisch bessere Ergebnisse als die Verwendung von Titanverbindungen und ist daher bevorzugt. Beispielsweise können komplexe Fluorosäuren oder deren Salze eingesetzt werden.The use of zirconium compounds in the different embodiments of the present invention gives technically better results than the use of titanium compounds and is therefore preferred. For example, complex fluoro acids or their salts can be used.

Im erfindungsgemäßen Verfahren sind des Weiteren solche Behandlungslösungen bevorzugt die als Komponente (i) mindestens 150 ppm, vorzugsweise mindestens 200 ppm, aber nicht mehr als 350 ppm, vorzugsweise nicht mehr als 300 ppm Zirconium in Form eines Fluorokomplexes enthalten.In the process according to the invention, further preferred are those treatment solutions which contain as component (i) at least 150 ppm, preferably at least 200 ppm, but not more than 350 ppm, preferably not more than 300 ppm of zirconium in the form of a fluorocomplex.

Der erfindungsgemäße Phosphat-Gehalt der Behandlungslösung ist im Vergleich zu im Stand der Technik beschriebenen Zink- oder Eisen-Phosphatierbädern äusserst niedrig. Bereits eine geringe Konzentration an Phosphationen von mindestens 10 ppm führt im Zusammenwirken mit den Fluorokomplexen von Zirconium und oder Titan zur Ausbildung einer dünnen amorphen Zirconium- und/oder Titanphosphatschicht und damit zur gewünschten Passivierung der Metalloberfläche, insbesondere der Eisenoberfläche. So erfolgt eine homogene Passivierung bereits bei Phosphat-Gehalten von bevorzugt 30 ppm, besonders bevorzugt mindestens 60 ppm. Aus Gründen der Prozesswirtschaftlichkeit und zur Vermeidung von Phosphatschlämmen im Behandlungsbad sollte der Phosphat-Gehalt jedoch 1000 ppm nicht überschreiten und vorzugsweise nicht mehr als 180 ppm, besonders bevorzugt nicht mehr als 120 ppm Phosphationen betragen.The phosphate content of the treatment solution according to the invention is extremely low in comparison with zinc or iron phosphating baths described in the prior art. Already a low concentration of phosphate ions of at least 10 ppm in combination with the fluorocomplexes of zirconium and or titanium leads to the formation of a thin amorphous zirconium and / or titanium phosphate layer and thus to the desired passivation of the metal surface, in particular the iron surface. Thus, a homogeneous passivation takes place already at phosphate contents of preferably 30 ppm, more preferably at least 60 ppm. For reasons of process economy and to avoid phosphate sludge in the treatment bath, however, the phosphate content should not exceed 1000 ppm and preferably not more than 180 ppm, particularly preferably not more than 120 ppm phosphate ions.

Überraschenderweise zeigt sich, dass aus der Zink- und Eisenphosphatierung bekannte Beschleuniger die Ausbildung einer homogenen Passivierung begünstigen. Derartige Beschleuniger stellen Oxidationsmittel dar, die in der Phosphatierung die Aufgabe eines "Wasserstofffängers" erfüllen, indem diese den durch den Säureangriff auf die metallische Oberfläche entstehenden Wasserstoff unmittelbar oxidieren und dabei selbst reduziert werden. Das Unterbinden einer massiven Wasserstoffentwicklung an der Werkstoffoberfläche erleichtert bei der schichtbildenden Phosphatierung die Ausbildung der kristallinen Phosphatschicht mit mehreren Mikrometern Schichtdicke. Gleiches gilt für die Anwesenheit der Beschleuniger in der nicht-schichtbildenden Eisenphosphatierung, bei der Schichtdicken von nicht wesentlich mehr als einem Mikrometer erzeugt werden. Offensichtlich vermögen die im Stand der Technik bekannten Beschleuniger, auch die homogene Ausbildung einer amorphen, nur wenige Nanometer umfassenden Passivschicht auf Basis von Zirconium- und/oder Titanphosphat zu unterstützen. Allerdings ist die Aktivität der Beschleuniger im Behandlungsbad wesentlich geringer einzustellen als es beispielsweise in der Zinkphosphatierung der Fall ist, so dass typische Oxidationsmittel in Gehalten von nicht mehr als 1000 ppm einzusetzen sind, mindestens aber ein Gehalt von 10 ppm in der Behandlungslösung vorliegen muss, um die Zirconium- und/oder Titan-basierte Passivierung der eisenhaltigen Metalloberfläche zu begünstigen. Typische Vertreter der Oxidationsmittel sind Chlorationen, Nitritionen, Nitroguanidin, N-Methylmorpholin-N-oxid, m-Nitrobenzoat-lonen, p-Nitrophenol, m-Nitrobenzolsulfonat-Ionen, Wasserstoffperoxid in freier oder gebundener Form, Hydroxylamin in freier oder gebundener Form, reduzierende Zucker. Insbesondere mit dem m-Nitrobenzolsulfonat als Beschleuniger werden bei Gehalten von nicht weniger als 20 ppm, vorzugsweise nicht weniger als 50 ppm und nicht mehr als 500 ppm, vorzugsweise nicht mehr als 300 ppm deutlich verbesserte Passivierungseigenschaften der Behandlungslösung erreicht.Surprisingly, it has been found that accelerators known from zinc and iron phosphating promote the formation of a homogeneous passivation. Such accelerators are oxidizing agents that perform the task of a "hydrogen scavenger" in the phosphating process by eliminating the hydrogen produced by the acid attack on the metallic surface oxidize directly and thereby reduce itself. The inhibition of massive hydrogen evolution on the material surface facilitates the formation of the crystalline phosphate layer with several micrometers layer thickness during the layer-forming phosphating. The same applies to the presence of the accelerators in the non-layer-forming iron phosphating, in which layer thicknesses of not significantly more than one micrometer are produced. Obviously, the accelerators known in the prior art are also able to support the homogeneous formation of an amorphous passive layer based on zirconium and / or titanium phosphate, which comprises only a few nanometers. However, the activity of the accelerators in the treatment bath is to be set much lower than is the case, for example, in zinc phosphating, so that typical oxidizing agents have to be used in amounts of not more than 1000 ppm, but at least 10 ppm must be present in the treatment solution promote zirconium- and / or titanium-based passivation of the ferrous metal surface. Typical representatives of the oxidizing agents are chlorate ions, nitrite ions, nitroguanidine, N-methylmorpholine N-oxide, m-nitrobenzoate ions, p-nitrophenol, m-nitrobenzenesulfonate ions, hydrogen peroxide in free or bound form, hydroxylamine in free or bound form, reducing Sugar. In particular, with the m-nitrobenzenesulfonate as the accelerator, at the contents of not less than 20 ppm, preferably not less than 50 ppm and not more than 500 ppm, preferably not more than 300 ppm, significantly improved passivation properties of the treatment solution are achieved.

Eine weitere Verbesserung der Passivschichteigenschaften und der Haftung zu nachträglich aufgebrachten Lackschichten resultiert bei Zugabe von partikulären anorganischen, wasserunlöslichen Verbindungen der Elemente Silizium, Aluminium, Zink, Titan, Zirconium, Eisen, Kalzium und/oder Magnesium, wobei der Gehalt an diesen Verbindungen in der Behandlungslösung bezogen auf das Element mindestens 10 ppm beträgt, aber 200 ppm nicht überschreiten sollte, um die Behandlungslösung durch Agglomerations- und Sedimentationsprozesse der partikulären Bestandteile nicht zu destabilisieren. Vorzugsweise werden die oxidischen Verbindungen der genannten Elemente in nanopartikulärer Form eingesetzt.A further improvement of the passive layer properties and the adhesion to subsequently applied lacquer layers results when adding particulate inorganic, water-insoluble compounds of the elements silicon, aluminum, zinc, titanium, zirconium, iron, calcium and / or magnesium, the content of these compounds in the treatment solution based on the element is at least 10 ppm, but should not exceed 200 ppm in order not to destabilize the treatment solution by agglomeration and sedimentation of the particulate components. Preferably, the oxidic compounds of said elements used in nanoparticulate form.

Die deutsche Patentanmeldung DE 100 05 113 basiert auf der Erkenntnis, dass Homo- oder Copolymere von Vinylpyrrolidon eine hervorragende Korrosionsschutzwirkung aufweisen. Ebenso werden Polymere mit Hydroxyl- und/oder Carboxylfunktionalitäten vielfach in erheblichen Mengen (> 1g/l) den Passivierungsbädern hinzugesetzt, um eingebaut in der anorganischen Passivschicht als Binder zu weiteren nachträglich aufgebrachten organischen Beschichtungen zu wirken. Der Zusatz weiterer Polymere erhöht jedoch den Prozessaufwand erheblich, da in Abhängigkeit vom Übertrag ("Drag Over") der polymeren Bestandteile aus der Vorbehandlungslösung in das Tauchlackbad die Stabilität des Tauchlackbades oder die Güte der Lackbeschichtung selbst negativ beeinflusst werden kann. Da jegliche Polymerzugabe in der Behandlungslösung demnach in einem Verfahren mit nachträglicher Elektrotauchlackierung zumindest einen intensiven Spülschritt unmittelbar nach der erfindungsgemäßen Vorbehandlung erzwingt, sollte das erfindungsgemäße Verfahren zur Reduktion der Spüldauer und der Spülwassermenge hinsichtlich der molaren Verhältnisse von Zirconium- und/oder Titan zu Phosphationen derart eingestellt werden, dass von einer Polymerzugabe gänzlich abgesehen werden kann. Daher betrifft die vorliegende Erfindung nur solche Verfahren, in denen die Menge an organischen Polymeren in der Behandlungslösung nicht größer als 1 ppm ist.The German patent application DE 100 05 113 based on the finding that homopolymers or copolymers of vinylpyrrolidone have an excellent corrosion protection effect. Likewise, polymers having hydroxyl and / or carboxyl functionalities are often added in substantial amounts (> 1 g / l) to the passivation baths in order to act as binders in the inorganic passive layer to act as further binders to subsequently applied organic coatings. The addition of other polymers, however, significantly increases the process cost, since depending on the transfer ("drag over") of the polymeric components from the pretreatment solution in the dip coating the stability of the dip bath or the quality of the paint coating itself can be adversely affected. Since any addition of polymer in the treatment solution thus enforces at least one intensive rinse step immediately after the pretreatment according to the invention in a subsequent electrocoating process, the process of the present invention should be adjusted to phosphate ion ratios with respect to molar ratios of zirconium and / or titanium to reduce the rinse time and rinse water level be that of a polymer addition can be waived entirely. Therefore, the present invention relates only to those methods in which the amount of organic polymers in the processing solution is not larger than 1 ppm.

Darüberhinaus benötigt das erfindungsgemäße Verfahren keine weiteren anorganischen Zusätze ausgewählt aus Oxoanionen von Vanadium, Wolfram und/oder Molybdän, um eine hinreichende Passivierung der Metalloberfläche, insbesondere Eisenoberfläche, zu erzeugen. Bei der Behandlung spezieller Metalloberflächen, insbesondere spezieller Eisenlegierungen, können im erfindungsgemäßen Verfahren geringe Mengen dieser Oxoanionen, insbesondere Vanadate und Molybdate, als zusätzlicher Bestandteil in der Behandlungslösung zugegen sein, um Defekte in der Zirconium- und/oder Titan-basierten Phosphatschicht bereits während der Passivierung auszuheilen. Aus Gründen der Prozesswirtschaftlichkeit ist der Anteil an diesen Verbindungen in der Behandlungslösung des erfindungsgemäßen Verfahrens bezogen auf das jeweilige Element jedoch kleiner als 50 ppm, vorzugsweise kleiner als 10 ppm.Moreover, the inventive method requires no further inorganic additives selected from oxo anions of vanadium, tungsten and / or molybdenum, in order to produce a sufficient passivation of the metal surface, in particular iron surface. In the treatment of special metal surfaces, in particular special iron alloys, small amounts of these oxoanions, in particular vanadates and molybdates, may be present as an additional constituent in the treatment solution in the process according to the invention in order to detect defects in the zirconium- and / or titanium-based phosphate layer already during the passivation heal. Because of Process economics, however, the proportion of these compounds in the treatment solution of the method according to the invention based on the respective element is less than 50 ppm, preferably less than 10 ppm.

Im erfindungsgemäßen Verfahren kann die Behandlungslösung zusätzlich chelatisierende Substanzen enthalten. Überraschenderweise zeigt sich, dass durch die Anwesenheit chelatisierender Substanzen, insbesondere solcher auf Basis von α-Hydroxycarbonsäuren, die Beizrate im Behandlungsbad bei längerer Betriebsdauer eines Bades stabilisiert wird, so dass weitgehend unabhängig vom Gehalt der Metall-Ionen, die durch das Anbeizen der Metalloberfläche ins Bad gelangen, konstante Schichtauflagen der Zirconium- und/oder Titan-basierten Phosphatschicht resultieren. Des Weiteren kann durch Zugabe der chelatisierenden Substanzen die Schlammbildung bestehend aus schwerlöslichen Metallhydroxiden deutlich minimiert werden. Vorzugsweise sind die chelatisierenden Substanzen als Zusatz zur Behandlungslösung im erfindungsgemäßen Verfahren ausgewählt aus α-Hydroxycarbonsäuren, besonders bevorzugt ausgewählt aus Polyhydroxysäuren mit nicht mehr als 8 Kohlenstoffatomen, wobei insbesondere Gluconsäure bevorzugt ist.
Der Gehalt an chelatisierenden Substanzen in der Behandlunslösung des erfindungsgemäßen Verfahrens beträgt vorzugsweise mindestens 0,01 Gew.-%, besonders bevorzugt mindestens 0,05 Gew.-%, aber vorzugsweise nicht mehr als 2 Gew.-%, besonders bevorzugt nicht mehr als 1 Gew.-%.In the process according to the invention, the treatment solution may additionally contain chelating substances. Surprisingly, it has been found that the presence of chelating substances, in particular those based on α-hydroxycarboxylic acids, stabilizes the pickling rate in the treatment bath for a longer service life of a bath, so that largely independent of the content of the metal ions, the by pickling the metal surface into the Bad, constant coating conditions of the zirconium and / or titanium-based phosphate layer result. Furthermore, by adding the chelating substances, the sludge formation consisting of sparingly soluble metal hydroxides can be significantly minimized. Preferably, the chelating substances are added as an additive to the treatment solution in the process according to the invention selected from α-hydroxycarboxylic acids, more preferably selected from polyhydroxy acids having not more than 8 carbon atoms, in particular gluconic acid is preferred.
The content of chelating substances in the treatment solution of the process according to the invention is preferably at least 0.01% by weight, more preferably at least 0.05% by weight, but preferably not more than 2% by weight, more preferably not more than 1 wt .-%.

Das im erfindungsgemäßen Verfahren zu behandelnde metallische Bauteil wird gegebenenfalls zuvor in einem Reinigungsschritt von oberflächlichen Verunreinigungen, insbesondere von Schmier- und/oder Korrosionsschutz-Ölen befreit. Unterbleibt eine solche Reinigung, so kann eine über die gesamte Metalloberfläche des Bauteils homogen ausgebildete Passivierung im erfindungsgemäßen Verfahren nicht erzielt werden. Um den der erfindungsgemäßen Vorbehandlung vorgelagerten Reinigungsschritt einzusparen, kann die saure Behandlungslösung des erfindungsgemäßen Verfahrens zusätzlich mindestens eine oberflächenaktive Substanz enthalten, so dass die effektive Reinigung der Metalloberflächen des Bauteils und deren Passivierung miteinander einhergehen. Der Einsatz von oberflächenaktiven Substanzen in passivierenden Vorbehandlungslösungen ist nicht selbstverständlich und insofern im erfindungsgemäßen Verfahren überraschend. So erfolgt beispielsweise in Gegenwart von Niotensiden in phosphatfreien Behandlungsbädern gemäß der DE 1933013 (Bonderite NT®) keine hinreichende Passivierung der Metalloberfläche. Als oberflächenaktive Substanzen können grundsätzlich sämtliche gängigen Tenside, vorzugsweise Niotenside verwendet werden, die in der Behandlungslösung des erfindungsgemäßen Verfahrens stabil sind und eine niedrige kritische Mizellbildungskonzentration unterhalb von 10-3 mol/l, bevorzugt unterhalb von 10-4 mol/l aufweisen.The metallic component to be treated in the process according to the invention is optionally previously freed of superficial impurities, in particular lubricants and / or corrosion protection oils, in a cleaning step. If such a cleaning is omitted, a passivation homogeneously formed over the entire metal surface of the component can not be achieved in the method according to the invention. In order to save the cleaning step preceding the pretreatment according to the invention, the acidic treatment solution of the process according to the invention may additionally contain at least one surface-active substance, so that the effective Cleaning the metal surfaces of the component and their passivation associated with each other. The use of surface-active substances in passivating pretreatment solutions is not self-evident and thus surprising in the process according to the invention. Thus, for example, in the presence of nonionic surfactants in phosphate-free treatment baths according to the DE 1933013 (Bonderite NT ® ) no adequate passivation of the metal surface. As surface-active substances it is possible in principle to use all customary surfactants, preferably nonionic surfactants, which are stable in the treatment solution of the process according to the invention and have a low critical micelle formation concentration below 10 -3 mol / l, preferably below 10 -4 mol / l.

Das erfindungsgemäße Verfahren zur passivierenden Vorbehandlung wird bevorzugt bei Badtemperaturen der Behandlungslösung von nicht mehr als 40 °C durchgeführt. Enthält die Vorbehandlungslösung zusätzlich oberflächenaktive Substanzen, so beträgt die Badtemperatur für eine hinreichende Reinigung der Metalloberflächen des zu behandelnden Bauteil bevorzugt zumindest 30 °C, wobei höhere Badtemperaturen als 80 °C zum einen nicht erforderlich und sich zum anderen negativ auf die Energieeffizienz des Verfahrens auswirken.The passivating pretreatment process according to the invention is preferably carried out at bath temperatures of the treatment solution of not more than 40.degree. If the pretreatment solution additionally contains surface-active substances, then the bath temperature for sufficient cleaning of the metal surfaces of the component to be treated is preferably at least 30 ° C., wherein higher bath temperatures than 80 ° C. are not required and have a negative effect on the energy efficiency of the process.

Bei dem erfindungsgemäßen Behandlungsverfahren können die Metalloberflächen sowohl durch Eintauchen oder Aufspritzen mit der Vorbehandlungslösung in Kontakt gebracht werden.In the treatment method of the present invention, the metal surfaces may be brought into contact with the pretreatment solution by either dipping or spraying.

In einem weiteren Aspekt umfasst die vorliegende Erfindung ebenso ein Verfahren zur korrosionsschützenden Beschichtung von nicht-geschlossenen metallischen Hohlkörpern, die zumindest teilweise metallische Oberflächen aus Eisen aufweisen, wobei dem zuvor beschriebenen erfindungsgemäßen Verfahren zur korrosionsschützenden Vorbehandlung eine Elektrotauchlackierung mit oder ohne dazwischenliegendem Spülschritt nachfolgt. Überraschenderweise zeigt die nach der erfindungsgemäßen Vorbehandlung resultierende amorphe und äußerst dünne Zirconium- und/oder Titan-basierte Phosphatpassivierung nach der Elektrotauchlackierung eine im Vergleich zu elektrotauchlackierten kristallinen Phosphatschichten akzeptable Korrosionsbeständigkeit und Lackhaftung. Zu Alternativverfahren, die ebenfalls in einer Vorbehandlungsstufe amorphe Passivschichten allerdings auf Basis von oxydischen Zirconium-haltigen Konversionsschichten ausbilden (Bonderite NT®), ist das erfindungsgemäße Beschichtungsverfahren bezüglich der Korrosionsbeständigkeit und der Lackhaftung auf Eisen oder Stahl hingegen mindestens gleichwertig. Ein entscheidender Vorteil der erfindungsgemäßen Vorbehandlung zu solchen Alternativverfahren ist jedoch der sich bei der Elektrotauchlackierung ergebende geringere Lackverbrauch bei identischem Umgriffverhalten.In a further aspect, the present invention also encompasses a process for the corrosion-protective coating of non-closed metallic hollow bodies, which at least partially comprise metallic iron surfaces, wherein the above-described inventive process for corrosion-protective pretreatment is followed by an electrodeposition coating with or without intermediate rinsing step. Surprisingly, the resulting after the pretreatment according to the invention amorphous and extremely thin zirconium and / or titanium-based phosphate passivation after Electrocoating an acceptable corrosion resistance and paint adhesion compared to electrocoated crystalline phosphate coatings. To alternative methods, which are also, however, develop in a pretreatment stage amorphous passive layers based on oxide zirconium-containing conversion coatings (Bonderite NT ®) coating process of the invention the corrosion resistance and paint adhesion on iron or steel is relative, however, at least equivalent. A decisive advantage of the pretreatment according to the invention for such alternative processes, however, is the lower paint consumption resulting in the electrocoating with identical wraparound behavior.

Vorzugsweise sollen erfindungsgemäß solche nicht-geschlossene metallische Hohlkörper bestehend zumindest teilweise aus Eisenoberflächen beschichtet werden, bei denen das Verhältnis von innerer Mantelfläche des nicht geschlossenen Hohlkörpers zur Öffnungsfläche desselben nicht kleiner als 5 ist, die also beispielsweise zumindest würfelförmig sind.Preferably, according to the invention, such non-closed metallic hollow bodies are to be at least partially coated with iron surfaces in which the ratio of the inner surface area of the non-closed hollow body to the opening area of the same is not less than 5, that is, for example, at least cube-shaped.

Das Umgriffverhalten also die Abscheidung des Tauchlackes an den der Gegenelektrode abgewandten Flächen des Bauteils oder an den Innenbereichen des metallischen Hohlkörpers, die aufgrund ihrer faradayschen Abschirmung zu Beginn der Abscheidung nahezu feldlinienfrei sind und daher lediglich über den Widerstandsaufbau der sich abscheidenden Lackschicht für die Schichtbildung zugänglich werden, wird entscheidend durch die erfindungsgemäße passivierende Vorbehandlung bestimmt und kann daher ebenso als kennzeichnendes Merkmal der erfindungsgemäßen Vorbehandlung oder der erfindungsgemäßen Beschichtung herangezogen werden. So ist die verfahrensspezifische Begrenzung der Schichtdicke des Elektrotauchlackes entscheidend für den Umgriff des Lackes, da bei gleicher Ladungsmenge, aber geringerer begrenzter bzw. maximaler Lackschichtdicke, zwangsläufig ein besserer Umgriff erfolgt.
In diesem Sinne kann als Merkmal des erfindungsgemäßen Verfahrens eine spezifische Schichtdickenbegrenzung als das Verhältnis der Schichtdicke des Elektrotauchlackes auf der äußeren Mantelfläche eines erfindungsgemäß beschichteten Hohlkörpers zur Schichtdicke des Elektrotauchlackes nach identischer, aber alleiniger Elektrotauchlackierung ohne vorherige Vorbehandlung auf der identischen äußeren Mantelfläche eines identischen unbehandelten, aber gereinigten und entfetteten Hohlkörpers angegeben werden. Dieses soll entsprechend der vorliegenden Erfindung nicht größer als 0,95, bevorzugt nicht größer als 0,9 und besonders bevorzugt nicht größer als 0,8 sein.The Umgriffverhalten so the deposition of the dip paint on the opposite sides of the counter electrode electrode or on the inner regions of the metallic hollow body, which are almost field-free due to their Faraday shielding at the beginning of the deposition and therefore only accessible via the resistance structure of the depositing paint layer for film formation is determined decisively by the passivating pretreatment according to the invention and can therefore also be used as a characterizing feature of the pretreatment according to the invention or of the coating according to the invention. Thus, the process-specific limitation of the layer thickness of the electrodeposition paint is crucial for the encirclement of the paint, as with the same amount of charge, but lesser limited or maximum film thickness, inevitably a better throwing takes place.
In this sense, as a feature of the method according to the invention, a specific layer thickness limitation as the ratio of the layer thickness of Electrocoating paint on the outer surface of a hollow body according to the invention coated to the thickness of the electrodeposition paint after identical, but only electrocoating without prior pretreatment on the identical outer surface of an identical untreated, but cleaned and degreased hollow body. This should not be greater than 0.95, preferably not greater than 0.9, and more preferably not greater than 0.8 according to the present invention.

Das erfindungsgemäße Verfahren zur Beschichtung eines metallischen Hohlkörpers kann so ausgeführt werden, dass zwischen den Verfahrensschritten der erfindungsgemäßen Vorbehandlung und dem Verfahrensschritt der Elektrotauchlackierung ein Spülschritt erfolgt, vorzugsweise mit entionisiertem Wasser oder Stadtwasser.The method according to the invention for coating a metallic hollow body can be carried out in such a way that a rinsing step takes place between the method steps of the pretreatment according to the invention and the electrocoating step, preferably with deionized water or city water.

In einer weiteren bevorzugten Ausführungsform des erfindungsgemäßen Beschichtungsverfahrens erfolgt nach der erfindungsgemäßen Vorbehandlung und vor dem Verfahrensschritt der Elektrotauchlackierung keine Trocknung des metallischen Hohlkörpers.In a further preferred embodiment of the coating method according to the invention, no drying of the metallic hollow body takes place after the pretreatment according to the invention and before the electrocoating process step.

Gegenstand der vorliegenden Erfindung sind ebenfalls die unmittelbar mit den erfindungsgemäßen Verfahren zur Vorbehandlung und Beschichtung behandelten metallischen Bauteile und nicht-geschlossenen metallischen Hohlkörper, wobei die zu behandelnden metallischen Bauteile und Hohlkörper zumindest teilweise metallische Oberflächen aus Eisen aufweisen.The present invention likewise relates to the metallic components and non-closed metallic hollow bodies treated directly with the method according to the invention for the pretreatment and coating, wherein the metallic components and hollow bodies to be treated at least partially have metallic iron surfaces.

Ferner umfasst die vorliegende Erfindung die Verwendung eines metallischen Bauteils, dessen gesamte Oberfläche, die zumindest teilweise aus metallischen Oberflächen aus Eisen besteht, entsprechend des erfindungsgemäßen Verfahrens mit der chromfreien wässrigen Behandlungslösung vorbehandelt wurde, für die Applikation weiterer korrosionsschützender Beschichtungen und/oder organischer Lacksysteme.Furthermore, the present invention encompasses the use of a metallic component whose entire surface, which consists at least partly of metallic iron surfaces, has been pretreated with the chromium-free aqueous treatment solution in accordance with the method according to the invention for the application of further corrosion-protective coatings and / or organic coating systems.

Ebenso umfasst die vorliegende Erfindung die Verwendung eines nicht-geschlossenen metallischen Hohlkörpers, dessen gesamte Oberfläche, die zumindest teilweise aus metallischen Oberflächen aus Eisen besteht, entsprechend des erfindungsgemäßen Verfahrens zunächst mit der chromfreien wässrigen Behandlungslösung vorbehandelt und anschließend mit oder ohne dazwischenliegendem Spülschritt elektrotauchlackiert wurde, für die Herstellung von Radiatoren.Likewise, the present invention comprises the use of a non-closed metallic hollow body whose entire surface, which at least partially consists of metallic iron surfaces, according to the inventive method first pretreated with the chromium-free aqueous treatment solution and then electrocoated with or without intervening rinsing step, for the production of radiators.

Ausführungsbeispiele:EXAMPLES

Im Folgenden sind erfindungsgemäße Ausführungsbeispiele und Vergleichsbeispiele zur Vorbehandlung von Stahlblechen (CRS: Cold Rolled Steel) einschließlich deren nachfolgende Elektrotauchlackierung genannt.Embodiments according to the invention and comparative examples for the pretreatment of steel sheets (CRS: cold rolled steel) including their subsequent electrodeposition coating are mentioned below.

Vergleichsbeispiel "alkalische Reinigung":Comparative example "alkaline cleaning":

CRS Bleche werden im Tauchverfahren für 5 min bei 50 °C in einer wässrigen Lösung zusammengesetzt aus 3 Gew.-% Ridoline 1562® und 0,3 Gew.-% Ridosol 1270® unter Rühren der Reinigungslösung behandelt.CRS sheets are treated by immersion for 5 min at 50 ° C in an aqueous solution composed of 3 wt .-% Ridoline 1562 ® and 0.3 wt .-% Ridosol 1270 ® while stirring the cleaning solution.

Vergleichsbeispiel "Bonderite NT-1®":Comparative Example "Bonderite NT-1 ®":

CRS Bleche werden zunächst im Tauchverfahren gemäß dem Vergleichsbeispiel "alkalische Reinigung" gereinigt, wonach das gereinigte Blech für 1 min unter fließendem vollentsalztem Wasser (k < 1 µScm-1) abgespült wird. Anschließend erfolgt im Tauchverfahren für 1 min bei 20 °C die Behandlung mit Bonderite NT-1® (Fa. Henkel KGaA) einer Zirconium-haltigen, aber phosphatfreien wässrigen Lösung. Das derart vorbehandelte Blech wird hiernach für 1 min unter fließendem vollentsalztem Wasser (k < 1 µScm-1) abgespült.CRS sheets are first cleaned in the immersion process according to the comparative example "alkaline cleaning", after which the cleaned sheet is rinsed for 1 minute under running demineralized water (k <1 μScm -1 ). Subsequently, the treatment with Bonderite NT-1 ® (Henkel KGaA) of a zirconium-containing, but phosphate-free aqueous solution is carried out by immersion for 1 min at 20 ° C. The thus pretreated sheet is then rinsed for 1 min under running demineralised water (k <1 μScm -1 ).

Vergleichsbeispiel "Zn-phosphatiert":Comparative Example "Zn-phosphated":

CRS Bleche werden zunächst im Tauchverfahren gemäß dem Vergleichsbeispiel "alkalische Reinigung" gereinigt, wonach das gereinigte Blech für 1 min unter fließendem vollentsalztem Wasser (k < 1 µScm-1) abgespült wird. Anschließend erfolgt im Tauchverfahren die Behandlung mit dem kommerziellen Produkt Granodine 958® (Fa. Henkel KGaA) entsprechend der Gebrauchsanweisung. Diese Behandlung schließt einen Aktivierungsschritt vor der eigentlichen Phosphatierung mit ein. Das derart vorbehandelte Blech wird hiernach für 1 min unter fließendem vollentsalztem Wasser (κ < 1 µScm-1) abgespült.CRS sheets are first cleaned in the immersion process according to the comparative example "alkaline cleaning", after which the cleaned sheet is rinsed for 1 minute under running demineralized water (k <1 μScm -1 ). The treatment with the commercial product Granodine 958 ® (Messrs. Henkel KGaA) according to the instructions Subsequently, the dipping method. This treatment includes an activation step before the actual phosphating. The thus pretreated sheet is then rinsed for 1 min under running demineralized water (κ <1 μScm -1 ).

Erfindungsgemäßes Beispiel "Zr-phosphatiert":Inventive example "Zr-phosphated":

CRS Bleche werden zunächst im Tauchverfahren gemäß dem Vergleichsbeispiel "alkalische Reinigung" gereinigt, wonach das gereinigte Blech für 1 min unter fließendem vollentsalztem Wasser (k < 1 µScm-1) abgespült wird. Anschließend erfolgt im Spritzverfahren die Behandlung mit einer erfindungsgemäßen wässrigen Lösung zusammengesetzt aus 300 ppm Zr als H2ZrF6, 100 ppm PO4 als H3PO4, 100 ppm Natrium-m-nitrobenzolsulfonat (m-NBS) und 3000 ppm Ridosol 2000® (Reiniger der Fa. Henkel KGaA) für 2 min bei 50 °C, wobei der pH-Wert mit ammoniakalischer Lösung auf pH 4,5 eingestellt wird. Das derart vorbehandelte Blech wird hiernach für 1 min unter fließendem vollentsalzten Wasser (k < 1 µScm-1) abgespült.CRS sheets are first cleaned in the immersion process according to the comparative example "alkaline cleaning", after which the cleaned sheet for 1 min rinsed with running demineralised water (k <1 μScm -1 ). Subsequently, in the spraying process, the treatment is carried out with an aqueous solution according to the invention composed of 300 ppm Zr as H 2 ZrF 6 , 100 ppm PO 4 as H 3 PO 4 , 100 ppm Sodium m-nitrobenzenesulfonate (m-NBS) and 3000 ppm Ridosol 2000 ® (cleaner Fa. Henkel KGaA) for 2 min at 50 ° C, wherein the pH is adjusted to pH 4.5 with ammoniacal solution. The thus pretreated sheet is then rinsed for 1 min under running demineralized water (k <1 μScm -1 ).

Sämtliche vorbehandelten Bleche werden sodann mit einem kathodischen Tauchlack Cathogard 500 der Fa. BASF beschichtet und bei 180°C für 30 min eingebrannt.
Die mittlere Lackschichtdicke wird mittels des Schichtdickenmessgerätes PosiTector 6000 (DeFelsko Ltd., Kanada) durch Mehrfachmessung an unterschiedlichen Stellen auf der der Anode zugewandten Seite des Bleches ermittelt. Für die Bestimmung der Lackschichtdicke des "Zn-phosphatierten" Stahlbleches wird vor der Elektrotauchlackierung zunächst die Schichtdicke der Zinkphosphatschicht mit Hilfe des PosiTector 6000 durch Mehrfachmessung bestimmt und von der ermittelten Schichtdicke nach der Lackierung subtrahiert.All pretreated sheets are then coated with a cathodic immersion coating Cathogard 500 from BASF and baked at 180 ° C for 30 min.
The average coating thickness is determined by means of the Coating Thickness Gauge PosiTector 6000 (DeFelsko Ltd., Canada) by multiple measurements at different points on the anode-facing side of the sheet. For the determination of the lacquer layer thickness of the "Zn-phosphated" steel sheet, the layer thickness of the zinc phosphate layer is first determined by multiple measurement before the electrodeposition coating and subtracted from the determined layer thickness after painting.

Aus der Tabelle 1 geht hervor, dass die erfindungsgemäße Vorbehandlung gegenüber den "nicht-schichtbildenden" Vorbehandlungen bei identischer Elektrotauchlackierdauer die niedrigste Schichtdicke besitzt. Lediglich das schichtbildend phosphatierte CRS Blech weist nach der Elektrotauch-lackierung eine noch geringere Lackschichtdicke auf.It can be seen from Table 1 that the pretreatment according to the invention has the lowest layer thickness compared to the "non-layer-forming" pretreatments with identical electrodeposition coating time. Only the layer-forming phosphated CRS sheet has an even lower coating thickness after the electro-dip coating.

Diese experimentellen Daten machen deutlich, dass über die erfindungsgemäße Vorbehandlung ein geringerer Lackverbrauch und damit automatisch auch ein verbesserter Umgriff im Vergleich zum nicht-schichtbildenden Passivierungsverfahren aus dem Stand der Technik erreicht wird. Tabelle 1 Schichtdicke des Elektrotauchlackes und Ladungsausbeute der Elektrotauchlackierung in Abhängigkeit von der Art der Vorbehandlung Vorbehandlung alkalische Reinigung Zr-phosphatiert Zn-phosphatiert Bonderite NT-1® Einzelbleche (CRS) 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1Ladungsmenge / As 102 102 102 102 91 91 90 90 86 86 85 85 95 95 95 95 Mittlere Ladungsmenge / As 102 90,5 85,5 95 2Schichtdicke / µm 29,7 29,4 29,0 29,5 26,2 26,8 26,1 25,7 24,6 25,3 25,0 24,7 27,8 26,9 28,3 26,6 Mittlere Schichtdicke / µm 29,4 26,2 24,9 27,4 Mittlere Ladungsausbeute / µm(As)-1 0,288 0,290 0,291 0,288 1 Ladungsmenge nach einer Elektrotauchlackierdauer von 2 min bei einer angelegten Gleichspannung von 240 V 2 Schichtdickenbestimmung des Elektrotauchlackes des Zn-phosphatierten Bleches über Differenzbildung der Schichtdicken gemessen nach der Vorbehandlung und nach der Elektrotauchlackierung. These experimental data make it clear that the pretreatment according to the invention achieves a lower paint consumption and thus automatically also an improved throw-over compared with the prior art non-film-forming passivation process. Table 1 Layer thickness of the electrodeposition coating and charge yield of the electrodeposition coating depending on the type of pretreatment preparation alkaline cleaning Zr-phosphate Zn-phosphated Bonderite NT-1 ® Single sheets (CRS) 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 charge quantity / As 102 102 102 102 91 91 90 90 86 86 85 85 95 95 95 95 Average amount of charge / As 102 90.5 85.5 95 2 layer thickness / μm 29.7 29.4 29.0 29.5 26.2 26.8 26.1 25.7 24.6 25.3 25.0 24.7 27.8 26.9 28.3 26.6 Average layer thickness / μm 29.4 26.2 24.9 27.4 Average charge yield / μm (As) -1 0,288 0,290 0.291 0,288 1 charge quantity after an electrocoating time of 2 minutes with an applied DC voltage of 240 V. 2 Layer thickness determination of the electrodeposition coating of the Zn-phosphated sheet by subtraction of the layer thicknesses measured after the pretreatment and after the electrodeposition coating.

Die Korrosionsbeständigkeit der entsprechend einer Formulierung gemäß dem vorherigen Beispiel ("Zr-phosphatiert"), aber mit variierendem Anteil von Zirconium, Phosphat und Natrium-m-nitrobenzolsulfonat vorbehandelten und gemäß den vorherigen Beispielen elektrotauchlackierten Bleche, ist in Abbildung 1 wiedergegeben. Die korrosive Unterwanderung am Ritz gemessen nach einer Auslagerung der derart beschichteten CRS Bleche über einen Zeitraum von 504 h gemäß Salzsprühnebelprüfung (DIN 50021 SS) belegt, dass für diejenigen Vorbehandlungslösungen, für die ein Molverhältnis von Zirconium zu Phosphat von 1 : 1 bis 10 : 1 vorliegt, eine optimale Korrosionsbeständigkeit erreicht wird. Die Unterwanderungswerte sind damit vergleichbar und sogar besser als diejenigen, die sich bei der korrosiven Unterwanderung nach einer Eisenphosphatierung nach 504 h einstellen und die typischerweise bei 1,5 mm liegen, und unwesentlich größer als nach der Vorbehandlung mit Bonderite NT-1®, die Unterwanderungswerte von 0,9 mm liefert.The corrosion resistance of the sheets pretreated according to a formulation according to the previous example ("Zr-phosphated") but with a varying proportion of zirconium, phosphate and sodium m-nitrobenzenesulfonate and electrocoated according to the previous examples, is disclosed in US Pat illustration 1 played. The corrosive infiltration at the scribe measured after a removal of the thus coated CRS sheets for a period of 504 hours according to salt spray test (DIN 50021 SS) shows that for those pretreatment solutions for which a zirconium to phosphate molar ratio of 1: 1 to 10: 1 is present, optimum corrosion resistance is achieved. The infiltration values are so similar and even better than those that adapt to the corrosive infiltration after an iron phosphating after 504 hours and typically be 1.5 mm, and slightly larger than after pretreatment with Bonderite NT-1 ®, the infiltration levels of 0.9 mm.

In analoger Weise kann festgestellt werden, dass das Umgriffverhalten ebenfalls für CRS Bleche, die mit Zusammensetzungen mit den entsprechenden erfindungsgemäßen molaren Verhältnissen vorbehandelt wurden, optimal ist (Abbildung 2). Der Umgriff wird dabei an der von der Anode abgewandten Seite des Bleches an unterschiedlichen Stellen mehrfach vermessen und gemittelt.In an analogous manner it can be stated that the throw-over behavior is also optimal for CRS sheets which have been pretreated with compositions having the corresponding molar ratios according to the invention ( Figure 2 ). The wraparound is measured and averaged at different points on the side facing away from the anode side of the sheet at different locations.

Claims (14)

  1. A method for the anticorrosive pretreatment of metal parts that at least partially have metal surfaces composed of iron, characterized in that the part is brought into contact with a chromium-free aqueous treatment solution containing
    (i) not less than 50 ppm and not more than 1000 ppm of zirconium and/or titanium in the form of fluorine complexes thereof,
    (ii) not less than 10 ppm and not more than 1000 ppm of phosphate ions, wherein the molar ratio of zirconium and/or titanium to phosphate ions is not greater than 10 : 1 and not less than 1 : 1,
    (iii) less than 50 ppm of oxoanions of vanadium, tungsten, and/or molybdenum, and
    (iv) not more than 1 ppm of organic polymers,
    at a pH value of not less than 3.5 and not greater than 6.0, wherein methods in which steel sheets are first cleaned with an alkaline cleaner, thereafter rinsed twice with municipal water, then treated with a bath, which, at a pH value of 5, is composed in such a way that, in addition to 10 ppm of iron ions, either 80 ppm of zirconium and 55 ppm of phosphate ions or 150 ppm of zirconium and 100 ppm of phosphate ions are contained, and then rinsed with municipal water, are excluded.
  2. The method according to claim 1, characterized in that the treatment solution contains, as an accelerator (iii), nitrobenzenesulfonic acid at a concentration of not less than 20 ppm, preferably not less than 50 ppm, and not more than 500 ppm, preferably not more than 300 ppm.
  3. The method according to one or both of the preceding claims, characterized in that the treatment solution contains, as component (i), preferably at least 150 ppm, especially preferably at least 200 ppm, but preferably not more than 350 ppm, especially preferably not more than 300 ppm, of zirconium in the form of a fluorine complex.
  4. The method according to one or more of the preceding claims, characterized in that the treatment solution contains preferably at least 30 ppm, especially preferably at least 60 ppm, but preferably not more than 180 ppm, especially preferably not more than 120 ppm, of phosphate ions.
  5. The method according to one or more of the preceding claims, characterized in that the treatment solution additionally contains nanoparticulate inorganic compounds of the elements silicon, aluminum, zinc, titanium, zirconium, iron, calcium, and/or magnesium, wherein the concentration of said compounds in the treatment solution with respect to the element is at least 10 ppm, but does not exceed 200 ppm.
  6. The method according to one or more of the preceding claims, characterized in that the treatment solution additionally contains chelating substances selected from α-hydroxycarboxylic acids, preferably selected from polyhydroxy acids having not more than 8 carbon atoms and especially preferably gluconic acid.
  7. The method according to one or more of the preceding claims, characterized in that the concentration of α-hydroxycarboxylic acids in the treatment solution is at least 0.01 wt%, preferably at least 0.05 wt%, but not more than 2 wt%, preferably not more than 1 wt%.
  8. The method according to one or more of the preceding claims, characterized in that the treatment solution additionally contains at least one surface-active substance.
  9. A method for the anticorrosive coating of unclosed metal hollow bodies that at least partially have metal surfaces composed of iron, characterized in that the hollow body is first
    (A) brought into contact with a chromium-free aqueous treatment solution containing
    (i) not less than 50 ppm and not more than 1000 ppm of zirconium and/or titanium in the form of fluorine complexes thereof,
    (ii) not less than 10 ppm and not more than 1000 ppm of phosphate ions, wherein the molar ratio of zirconium and/or titanium to phosphate ions is not greater than 10 : 1 and not less than 1 : 1,
    (iii) less than 50 ppm of oxoanions of vanadium, tungsten, and/or molybdenum, and
    (iv) not more than 1 ppm of organic polymers,
    at a pH value of not less than 3.5 and not greater than 6.0; and then
    (B) is electrophoretically painted, with or without an intermediate rinsing step.
  10. The method according to claim 9, characterized in that the ratio of the inner shell surface of the unclosed hollow body to the opening area of the unclosed hollow body is not less than 5.
  11. The method according to one or more of claims 9 and 10, characterized in that, after the pretreatment (A) and before the step (B) of the electrophoretic painting, no drying of the metal hollow body occurs.
  12. The method according to one or more of claims 9 to 11, characterized in that the ratio of the layer thickness of the electrophoretic paint on the outer shell surface of a hollow body coated according to steps (A) and (B) to the layer thickness of the electrophoretic paint after identical but unaccompanied electrophoretic painting according to step (B) on the identical outer shell surface of an identical untreated but cleaned and degreased hollow body is not greater than 0.95, preferably not greater than 0.9, and especially preferably not greater than 0.8.
  13. An unclosed metal hollow body that at least partially has metal surfaces composed of iron, characterized in that the hollow body has been coated according to a method according to one or more of claims 9 to 12.
  14. The use of an unclosed metal hollow body according to claim 13 to produce radiators.
EP08853163.7A 2007-11-26 2008-11-25 Zirconium phosphating of metal components, in particular iron Active EP2215285B1 (en)

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DE102007057185A DE102007057185A1 (en) 2007-11-26 2007-11-26 Zirconium phosphating of metallic components, in particular iron
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MY162565A (en) * 2010-09-15 2017-06-30 Jfe Steel Corp Steel sheet for containers and manufacturing method for same
US20120094130A1 (en) * 2010-10-15 2012-04-19 Universidade Estadual De Campinas Coating Compositions With Anticorrosion Properties
KR101263086B1 (en) * 2010-12-28 2013-05-09 주식회사 포스코 Plate type zirconium phosphate and preparation method thereof
DE102016206418A1 (en) 2016-04-15 2017-10-19 Henkel Ag & Co. Kgaa SUPPRESSION OF PLANT-SPECIFIC PHOSPHATE EXTRACTION IN A PROCESS FOR DIPPING LACQUER
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