JP2023503493A - Resource-saving method for activating metal surfaces prior to phosphating - Google Patents

Abstract

The present invention is a method for phosphating a metal surface in a layer-forming fashion using, as an activation step, a colloidal aqueous solution containing dispersed particulate components, the particulate components comprising multiple In addition to dispersed inorganic compounds of phosphates of valent metal cations, at least partially composed of styrene and/or α-olefins having up to 5 carbon atoms, at least partially maleic acid, its anhydrides. and/or containing a polymeric organic compound as a dispersant composed of its imides, said polymeric organic compound further comprising polyoxyalkylene units. The washing and rinsing steps preceding the activation step, as well as the activation step itself, are carried out by adding a colloidal aqueous solution containing at least 0.5 mmol/L of alkaline earth metal ions dissolved in water to It can be carried out using tap water in a resource-saving way. In the activation stage of the process of the present invention, the content of condensed phosphate dissolved in the colloidal aqueous solution is reduced to 0.5, based on the phosphate content in its particulate component, in each case based on the element P. To be less than 25, the addition of condensed phosphate can be omitted.

Description

The present invention is a method for phosphating a metal surface in a layer-forming fashion using a colloidal aqueous solution as an activation step, the process containing a dispersed particulate component, the particulate component comprising multiple In addition to dispersed inorganic compounds of phosphates of valent metal cations, maleic acid, its anhydrides and/or its It relates to a method comprising a high molecular weight organic compound as a dispersant partially composed of an imide, said high molecular weight organic compound further comprising polyoxyalkylene units. In the activation stage of the process of the present invention, the content of condensed phosphate dissolved in the colloidal aqueous solution is reduced to 0.5, based on the phosphate content in its particulate component, in each case based on the element P. To be less than 25, the addition of condensed phosphate can be omitted.

Layered phosphating is a method of applying crystalline anti-corrosion coatings to metallic surfaces, especially iron, zinc and aluminum metallic materials, which has been used and studied in detail for decades. Zinc phosphating, which is particularly well established for corrosion protection, is carried out using layer thicknesses of several micrometers and prevents corrosion of metallic materials in acidic aqueous compositions containing zinc ions and phosphate. based on acid wash. During the acid cleaning process, an alkali diffusion layer is formed on the metal surface, which extends into the interior of the solution, in which refractory crystallites are formed, and the crystallites are directly at the interface with the metal material. settle down and continue to grow there. A water-soluble compound that is a source of fluoride ions is often added to aid the acid cleaning reaction on metallic aluminum materials and to mask bath poisoning aluminum that in dissolved form interferes with layer formation on metallic materials. be. Zinc phosphating is always initiated by activation of the metal surface of the component to be phosphorylated. Wet-chemical activation is conventionally carried out by contacting the phosphate with a colloidal aqueous solution (the "activation step"), and the phosphate, as long as it remains immobilized on the metal surface, is not susceptible to subsequent phosphating. used as growth nuclei to form a crystalline coating in the alkali diffusion layer. Suitable dispersions in this case are colloidal, mostly neutral to phosphate crystallite-based dispersions with only minor crystallographic deviations in crystal structure from the type of zinc phosphate layer deposited. It is an alkaline aqueous composition. In this connection, for example WO 98/39498 teaches divalent and trivalent phosphates of the metals Zn, Fe, Mn, Ni, Co, Ca and Al, among others; It is technically preferred that phosphate is used for activation for subsequent zinc phosphating.

Activation steps based on dispersing divalent and trivalent phosphates require a high level of process control to keep activation performance at optimal levels, especially when processing a range of metal components. To ensure that the method is sufficiently robust, extraneous ions carried over from the aging process in previous treatment baths or aqueous colloidal solutions should not degrade the activation performance. Degradation is first noticeable in an increase in layer weight on subsequent phosphating, eventually leading to the formation of a defective or non-uniform phosphate layer. Therefore, if the process is carried out continuously, chemical treatment is required to extend the bath life and/or to reduce the colloidal active ingredient consumption to the extent that phosphating based on aqueous colloidal solutions can be economically practiced. It is necessary to add substances. When using particulate phosphate for activation, the addition step necessarily includes the addition of condensed phosphate for colloidal stabilization. Complexing agents are often used to counteract the accelerated formation of colloidal aggregates and thus the settling of colloidally dispersed bath species, to mask multivalent metal ions carried over from previous washing steps and to mask water hardness. is also added. The dosing of condensed phosphate and/or complexing agent requires accurate analytical monitoring because there are both process-critical minimum amounts to be maintained and system-specific upper limits, and the condensed phosphate and/or complexing agent If the amount of agent falls below this minimum amount or exceeds this upper limit, activation performance is adversely affected.

WO 98/39498

Therefore, the activation step of the pretreatment line for phosphating, in particular zinc phosphating, intended to be carried out on the basis of colloidal aqueous solutions of phosphates is replaced with metal surfaces for phosphating. There is a need to be more efficient with respect to its properties of activating , and to make the step more robust with respect to processes. This is because, inter alia, the aqueous colloidal solution leads to the activation of metal surfaces to be phosphatized as uniformly and comprehensively as possible using relatively small amounts of material, thus in the phosphating step It relates to the ability to result in the formation of homogeneous, finely crystalline coatings so that, in addition to excellent coating adhesion properties, high charge transfer resistance and thus correspondingly good coating gripping are achieved in subsequent electrical coatings. . In addition, aspects to improve the robustness of such methods should ensure that there is greater resistance to carried-over and accumulated extraneous ions and greater stability with respect to the structural and chemical state of the colloidal components. There is The aim of all this is to establish a pretreatment line for phosphating, in particular zinc phosphating, which can be carried out continuously with low technical complexity in a resource-saving manner.

This complex working profile is surprisingly addressed by the use of specific polymeric dispersants to stabilize the colloidal constituents of the particulate phosphate-based activation stage. Due to the highly efficient stabilization of the particulate constituents that lead to the activation, the special dispersants are able to produce uniform, closed phosphate coatings even with relatively low proportions of colloids, leading to Ensures that colloidal content is maintained and consistent without significant degradation in activation performance after the processing line reaches quiescent conditions. The use of specific dispersants thus makes it possible to completely dispense with the addition of condensed phosphate, thus significantly reducing the technical complexity of continuously carrying out the phosphating process.

Accordingly, the present invention is a method for the anti-corrosion pretreatment of a metallic material selected from zinc, iron or aluminum or a component at least partially composed of such a metallic material, said metallic material or component comprising , in successive process steps, first undergoing activation (i) and then phosphating (ii), in particular zinc phosphating, the activation in process step (i) turning said metallic material or component into a colloidal aqueous solution wherein the colloidal aqueous solution is added to the dispersed particulate component (a) solution,
(a1) at least one particulate inorganic compound composed of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and/or halorite; and (a2) at least partially composed of styrene and/or α-olefins having up to 5 carbon atoms, at least partially composed of maleic acid, its anhydrides and/or its imides and further comprising polyoxyalkylene units containing one macromolecular organic compound,
In said colloidal aqueous solution, the content of condensed phosphate dissolved in water is less than 0.25, in each case based on the phosphate content of said at least one particulate compound based on element P , on the method.

The dispersed particulate component (a) of the colloidal aqueous solution in activation (i) of the process according to the invention is a defined partial volume of the aqueous dispersion with a nominal cutoff limit of 10 kD (NMWC: nominal molecular weight cutoff). Solids remaining after drying the ultrafiltration retentate. Ultrafiltration is performed by adding deionized water (κ<1 μScm ⁻¹ ) until a conductivity of less than 10 μScm ⁻¹ is measured in the filtrate.

In the context of the present invention an organic compound is a polymer if its weight-average molar mass is greater than 500 g/mol. Molar masses are determined using a molar mass distribution curve of relevant reference value samples, which was established experimentally at 30° C. by size exclusion chromatography using a concentration-dependent refractive index detector, Calibrated against polyethylene glycol standards. Analysis of average molar masses is done computer-based according to the strip method with a cubic calibration curve. As column material, hydroxylated polymethacrylate is suitable, and as eluent, an aqueous solution of 0.2 mol/L sodium chloride, 0.02 mol/L sodium hydroxide and 6.5 mmol/L ammonium hydroxide is suitable. .

The process according to the invention is characterized in that the addition of condensed phosphate in the activation stage can be omitted. The condensed phosphates dissolved in the aqueous phase of the activation fulfill the task of masking the permanent water hardness and, based on experience, the content of the phosphates hopeite, phosphophyllite, scholzite and/or hallite. It serves the specific task of stabilizing at the colloidal level and thus keeping the phosphate permanently available for activation. It is remarkable and surprising for the person skilled in the art that in the process according to the invention based on the activation step based on particulate component (a) the addition of condensed phosphate can be omitted.

This advantage over conventional activating baths is particularly evident when phosphating the components in series, ie during continuous operation of the pretreatment line for phosphating. Therefore, in a preferred embodiment of the method according to the invention, a number of specific components, at least partly zinc, iron or aluminum, are processed in series. Sequential pretreatment is when multiple components are contacted with an aqueous colloidal solution placed in the activation stage system tank, with individual components being contacted with the solution one after the other and thus at different times, the components being It is then fed to the phosphating process. In this case, the system tank is the container in which the aqueous colloidal solution is placed for the purpose of activation for phosphating in series.

Overall, in the context of the present invention, the addition of condensed phosphates can thereby be completely omitted, and the activation therefore reduces the pretreated components, especially when processing multiple components in series. Contains only a small amount of condensed phosphate from the washing step prior to inclusion to the activation step. In a preferred embodiment of the process according to the invention, the content of condensed phosphates dissolved in water in the aqueous colloidal solution is in each case the phosphate content of at least one particulate compound (a1) based on the element P Based on the amount, it is less than 0.20, particularly preferably less than 0.15 and very preferably less than 0.10.

Furthermore, in this connection, the content of condensed phosphate dissolved in water in the aqueous colloidal solution, calculated as P, is less than 20 mg/kg, preferably less than 15 mg/kg, particularly preferably less than 15 mg/kg, based on the aqueous colloidal solution. Preferably less than 10 mg/kg.

In the context of the present invention, condensed phosphates are metaphosphates and polyphosphates, preferably polyphosphates, particularly preferably pyrophosphates. The condensed phosphates are preferably in the form of compounds of monovalent cations, preferably selected from Li, Na and/or K, particularly preferably Na and/or K.

The condensed phosphate content can be determined analytically from the difference in total phosphate content in the non-particulate constituents of aqueous colloidal solutions, with or without oxidative digestion, e.g. by peroxodisulfate. , the dissolved orthophosphate content is quantified by photometry. Alternatively, if polyphosphate is used as the condensed phosphate, enzymatic digestion with pyrophosphatase can be performed instead of oxidative digestion. The non-particulate component of the aqueous colloidal solution is the solids content of the aqueous colloidal solution in the permeate of the above-mentioned ultrafiltration after being dried to constant weight at 105° C., i.e. the particulate component (a) is the solid content after separation by

The high tolerance of the method according to the invention to carried-over extraneous ions is also due to the fact that the washing and rinsing steps carried out before the activation step and the activation step itself are carried out with tap water instead of deionized water. enable In this way the method according to the invention is carried out in a particularly resource-saving manner. Therefore, according to the invention, the colloidal aqueous solution in the activation is at least 0.5 mmol/L, particularly preferably at least 1.0 mmol/L, particularly more preferably at least 1.5 mmol/L dissolved in water, It preferably contains 10 mmol/L or less of alkaline earth metal ions.

If the resistance of the process according to the invention in any case reaches system-specific limits at very high ionic strengths, e.g. high permanent water hardness, and at the same time a high content of foreign ions carried over from the previous washing stage. , organic complexing agents can be added to mask foreign ions in order to maintain a long bath life. In this case, the economic advantage of being able to carry out the activation stage and, optionally, the preceding washing stage and rinse with tap water is the addition of the organic complexing agent in the system tank of the activation stage and their must be evaluated whether it is not hampered by Suitable organic complexing agents which are preferred in this context are selected from α-hydroxycarboxylic acids, which in turn are preferably gluconic acid, tartronic acid, glycolic acid, citric acid, tartaric acid, lactic acid, very particularly preferably gluconate and/or organic phosphonic acids, which in turn are preferably selected from etidronic acid, aminotris(methylenephosphonic acid), aminotris(methylenephosphonic acid), phosphonobutane-1,2,4-tricarboxylic acid, diethylenetriamine penta( methylenephosphonic acid), hexamethylenediaminetetra(methylenephosphonic acid) and/or hydroxyphosphonoacetic acid, particularly preferably etidronic acid.

In order to maintain stable activation performance, the amount of the organic complexing agent in the colloidal aqueous solution is preferably no more than twice the amount of alkaline earth metal ions, particularly preferably no more than 1.5 times, Very preferably it should be added to an extent that is not more than equimolar to the amount of alkaline earth metal ion.

The aqueous colloidal solution in activation (i) of the process according to the invention preferably has an alkaline pH, particularly preferably above 8.0, particularly more preferably above 9.0, but preferably below 11.0. However, it is possible to use compounds that affect the pH such as phosphoric acid, sodium hydroxide solution, ammonium hydroxide or ammonia to adjust the pH. "pH" as used in the context of the present invention corresponds to the negative common logarithm of hydronium ion activity at 20°C and can be determined with a pH-sensitive glass electrode.

For good activation performance it is necessary to use a correspondingly high proportion of polyvalent metal cations in the form of phosphates to be included in the dispersed particulate component (a) for activation. Accordingly, the content of phosphate contained in the at least one particulate inorganic compound (a1) is preferably at least 25 wt. % by weight, particularly more preferably at least 40% by weight, very preferably at least 45% by weight. The inorganic particulate constituents of the aqueous colloidal solution are then added to the particulate constituent (a) obtained from drying the retentate of the ultrafiltration, the infrared sensor detects at the exit of the reactor from a _CO2 -free carrier gas (blank). value) when pyrolysed in a reactor by feeding a _CO2 -free oxygen stream at 900° C. without admixture of catalyst or other additives until it provides a signal identical to the value ). Phosphate contained in the inorganic particulate component was determined from acid digestion as phosphorus content by atomic emission spectroscopy (ICP-OES) after acid digesting the component with 10 wt% _HNO3 aqueous solution at 25°C for 15 minutes. Determined directly.

The active ingredients of colloidal aqueous dispersions that effectively promote the formation of closed phosphate coatings on metal surfaces and, in this sense, activate metal surfaces are, as already mentioned, mainly from phosphates. which in turn leads to the formation of a microcrystalline coating, thus at least partially selected from hopeite, phosphophyllite, scholzite and/or hallolite, preferably at least partially hopeite, phosphophyllite and/or or scholzite, particularly preferably at least partially selected from hopeite and/or phosphophyllite, very preferably at least partially selected from hopeite. Activation within the meaning of the invention is therefore substantially based on the particulate form of phosphate involved in the activation step. Without considering water of crystallization, hopeite stoichiometrically combines Zn ₃ (PO ₄ ) ₂ and nickel- and manganese-containing variants Zn ₂ Mn(PO ₄ ) ₃ , Zn ₂ Ni(PO ₄ ) ₃ . Phosphophyllite consists of Zn ₂ Fe(PO ₄ ) ₃ , Scholzite consists of Zn ₂ Ca(PO ₄ ) ₃ , and Hallolite consists of Mn ₃ (PO ₄ ) ₂ . The presence of crystalline phases of hopeite, phosphophyllite, scholzite and/or halorite in the aqueous dispersions according to the invention is determined by ultrafiltration with the nominal cut-off limit of 10 kD (NMWC: nominal molecular weight cut-off) mentioned above. It can be demonstrated by X-ray diffraction (XRD) after isolation of element (a) and drying of the retentate to constant mass at 105°C.

Since the presence of a phosphate containing zinc ions and having a certain crystallinity is preferred, in the method according to the invention, to form a strongly adhering crystalline zinc phosphate coating after successful activation, colloidal water The dispersion contains at least 20% by weight, particularly preferably at least 30% by weight, in particular at least 30% by weight, in the inorganic particulate constituent of the aqueous colloidal solution, calculated as PO4, based _on the phosphate content of the inorganic particulate constituent. More preferably it contains at least 40% by weight of zinc.

Another advantage of the process according to the invention is that even a small proportion of the particulate inorganic compound (a1) in the activation (i) is sufficient to achieve full activation performance for the materials zinc, aluminum and iron. It is to be. Therefore, according to the invention, the content of dispersed particulate component (a) of the aqueous colloidal solution is in each case at least 0.05 g/kg, preferably at least 0.1 g/kg, based on the aqueous colloidal solution. , particularly preferably at least 0.2 g/kg, but preferably 10 g/kg or less, particularly preferably 2 g/kg or less, very preferably 1 g/kg or less.

However, it is preferred that activation within the meaning of the invention is not achieved by a colloidal solution of titanium phosphate, as this would otherwise ensure a layer-forming zinc phosphate treatment on iron, in particular steel. This is because it is not achieved. Therefore, in a preferred embodiment of the method according to the invention, the content of titanium in the inorganic particulate constituents of the aqueous colloidal solution is less than 0.01% by weight, particularly preferably less than 0.001% by weight, based on the aqueous colloidal solution. is. In a particularly preferred embodiment, the aqueous colloidal solution of activation (i) contains a total of less than 10 mg/kg, particularly preferably less than 1 mg/kg, of titanium.

The activation step in the method according to the invention is further characterized by its D50 value, above which the activation performance drops significantly. The D50 value of the aqueous colloidal solution is preferably less than 1 μm, particularly preferably less than 0.4 μm. In the context of the present invention, the D50 value denotes the particle size that does not exceed 50% by volume of the particulate constituents contained in the aqueous colloidal solution. According to ISO 13320:2009, the D50 value is determined using refractive index n _D =1.52−i·0.1 for spherical and scattering particles immediately after the sample is taken from the activation stage, according to Mie theory. can be determined at 20° C. from the volume-weighted cumulative particle size distribution by scattered light analysis.

Within the meaning of the present invention, the polymeric organic compound (a2) used as dispersant and having polyoxyalkylene units is at least partially styrene and/or α-olefins having up to 5 carbon atoms, and maleic acid, its anhydride and/or its imides, which lead to a very high stability of the colloidal aqueous solution during the activation stage of the process according to the invention.

The α-olefin in this case is preferably selected from ethene, 1-propene, 1-butene, isobutylene, 1-pentene, 2-methyl-but-1-ene and/or 3-methyl-but-1-ene , particularly preferably isobutylene. It is clear to those skilled in the art that the macromolecular organic compound (a2) contains these monomers as structural units in unsaturated form covalently bonded to each other or to other structural units. Suitable commercial representatives are, for example, Dispex® CX 4320 (BASF SE), a maleic acid-isobutylene copolymer modified with polypropylene glycol, Tego ( Dispers 752 W (Evonik Industries AG), or Edaplan ® 490 (Munzing Chemie GmbH), a maleic acid-styrene copolymer modified with EO/PO and imidazole units. In the context of the present invention, polymeric organic compounds (a2) which are at least partially composed of styrene are preferred.

The polymeric organic compound (a2) used as a dispersant preferably consists of 1,2-ethanediol and/or 1,2-propanediol, particularly preferably 1,2-ethanediol and 1,2- It has polyoxyalkylene units composed of both propanediol, and the content of 1,2-propanediol in the total polyoxyalkylene units is preferably at least 15% by weight with respect to the total polyoxyalkylene units. However, it is particularly preferably 40% by weight or less. Moreover, it is preferable that the side chain of the polymeric organic compound (a2) contains a polyoxyalkylene unit. A polyoxyalkylene unit content of at least 40% by weight, particularly preferably at least 50% by weight, but preferably no more than 70% by weight, in the entire polymeric organic compound (a2) is advantageous for dispersibility.

For immobilizing inorganic particulate constituents of aqueous colloidal solutions formed at least in part by polyvalent metal cations in the form of phosphates selected from hopeite, phosphophyllite, scholzite and/or hallite and a dispersing agent. , the polymeric organic compound (a2) preferably also contains N-heterocyclic units, which in turn are preferably selected from pyridine, imidazole, imidazoline, morpholine, pyrrole and/or pyrrolidone units, in particular It is preferably selected from imidazole and/or imidazoline units, particularly more preferably from imidazole units. Each of these N-heterocyclic units is preferably part of a side chain of the polymeric organic compound (a2), within the side chain preferably via at least 3 carbon atoms, particularly preferably polymeric The polyoxyalkylene units of the organic compound (a2) are aliphatically attached to the main chain such that they are at least partially endcapped with N-heterocycles, thus in a preferred embodiment the polyoxyalkylene side chains are A terminal N-heterocyclic group is present. The N-heterocyclic unit is preferably covalently bonded via the nitrogen atom of the heterocyclic ring to a side chain of the high molecular weight organic compound (a2), preferably a side chain having a polyoxyalkylene unit. The N-heterocyclic units are preferably present in at least partially quaternized form, particularly preferably as N-alkylated quaternary N-heterocyclic units.

In a preferred embodiment, the amine value of the organic polymeric compound (a2) is at least 25 mg KOH/g, particularly preferably at least 40 mg KOH/g, but preferably less than 125 mg KOH/g, particularly preferably 80 mg KOH/g. less than, and therefore in preferred embodiments, the bulk of the macromolecular organic compounds in the particulate component (a) also have these preferred amine values. The amine value is determined by weighing approximately 1 g of the relevant reference value - the organic polymeric compound (a2) or the total polymeric organic compound in the particulate component - in 100 mL of ethanol in each case. , the titration is carried out using 0.1N HCl titration solution against the indicator bromophenol blue until the color changes to yellow at the temperature of the ethanol solution of 20°C. The amount of HCl titrant solution used in milliliters multiplied by the factor 5.61 divided by the exact mass of the weight in grams gives the amine value in milligrams of KOH per gram of the relevant reference value. handle.

As long as it is a constituent of the organic polymeric compound (a2) as the free acid, rather than in anhydrous or imide form, the presence of maleic acid can impart increased water solubility of the dispersant, especially in the alkaline range. . Therefore, in order to ensure a sufficient number of polyoxyalkylene units, the macromolecular organic compound (a2), preferably the entire macromolecular organic compound in the particulate component (a), is April 2004) is at least 25 mg KOH/g, preferably less than 100 mg KOH/g, particularly preferably less than 70 mg KOH/g. The total macromolecular organic compound (a2), preferably also the total macromolecular organic compound in the particulate component (a), is in each case determined according to Method A of European Pharmacopoeia 9.0 01/2008:20503 It is also preferred to have a hydroxyl number of less than 15 mg KOH/g, particularly preferably less than 12 mg KOH/g, particularly more preferably less than 10 mg KOH/g.

In order to sufficiently disperse the inorganic particulate component in the colloidal aqueous dispersion, the content of the polymeric organic compound (a2), preferably in the particulate component (a) based on the particulate component (a) is at least 3% by weight, particularly preferably at least 6% by weight, but preferably not more than 15% by weight.

In a further aspect, the present invention relates to a method for anti-corrosion pretreatment based on phosphating and comprising an aqueous dispersion. Such a method according to the invention relates to an anticorrosion pretreatment of a metallic material selected from zinc, iron or aluminum or a component at least partially composed of such a metallic material, in which method the metallic material or component is , in successive method steps, first undergoing an activation (i) and then a phosphating (ii), in particular a zinc phosphating, the activation in method step (i) comprising at least one of the metal materials or components The metal material is brought into contact with an aqueous colloidal solution as described above, which can be obtained as a 20- to 100,000-fold diluted aqueous dispersion, and the aqueous colloidal solution is
- at least 5% by weight of dispersed particulate component (A), based on the aqueous dispersion,
(A1) at least one particulate inorganic compound composed of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and/or hallolite;
(A2) at least partially composed of styrene and/or α-olefins having 5 or less carbon atoms, at least partially composed of maleic acid, its anhydrides and/or its imides, containing polyoxyalkylene units a dispersed particulate component (A), which further comprises at least one high molecular weight organic compound; It contains at least one thickening agent (B) which is particularly preferably selected from urea urethane resins having an amine value of less than 2 mg KOH/g.

For the dispersed dispersed particulate component (A) and at least one particulate inorganic compound (A1) and polymeric organic compound (A2), the same definitions and preferred specifications as given above for the aqueous colloidal solution are used. Applies.

Due to the excellent colloidal stability of the particulate component (A) with the macromolecular organic compound (A2) as dispersant, the dilution can be done with deionized water ( κ<1 μScm ⁻¹ ), particularly preferably tap water. In light of the underlying technical application, tap water contains at least 0.5 mmol/L alkaline earth metal ions.

The presence of the thickening agent according to component (B), in combination with its particulate constituents, imparts a thixotropic flow behavior to the aqueous dispersion, whereby the primary particles cannot detach and agglomerate in the particulate constituents of the dispersion. Contributes to the prevention of irreversible formation of objects. The addition of a thickener preferably ensures that the aqueous dispersion has a maximum kinematic viscosity of at least 1000 Pa·s, preferably less than 5000 Pa·s at a temperature of 25° C. and a shear rate range of 0.001 to 0.25 per second. and preferably exhibit shear-thinning behavior at 25° C. at shear rates above those existing at maximum kinematic viscosity, i.e. the viscosity decreases as the shear rate increases, resulting in water The entire dispersion has thixotropic flow behavior. Viscosity over the specified shear rate range can be determined using a cone and plate viscometer with a cone diameter of 35 mm and a gap width of 0.047 mm.

The ^thickening agent according to component (B), as a 0.5 wt. It is a defined mixture of chemical compounds with a Brookfield viscosity of at least 100 mPa·s at a shear rate of 60 rpm (=revolutions per minute). When determining this thickener property, the mixture is prepared by adding the corresponding amount of polymeric compound to the aqueous phase at 25° C. with stirring, and then degassing the homogenized mixture in an ultrasonic bath. and should be mixed with water in such a way that it is allowed to stand for 24 hours. Viscosity measurements are then read within 5 seconds immediately after applying a shear rate of 60 rpm by the number 2 spindle.

The aqueous dispersions according to the invention preferably have a total of at least 0.5% by weight, but preferably no more than 4% by weight, particularly preferably no more than 3% by weight, of one or more thickeners according to component (B). The total content of macromolecular organic compounds in the non-particulate constituents of the aqueous dispersion also preferably does not exceed 4% by weight (based on the dispersion). The non-particulate component is the solids content of the aqueous dispersion in the permeate of the above ultrafiltration after drying to constant weight at 105° C., i.e. after the particulate component has been separated by ultrafiltration. is the solid content of

A particular class of polymeric compounds are particularly suitable thickeners according to component (B) and are readily commercially available. In this connection, the thickening agent according to component (B) is particularly preferably selected from macromolecular organic compounds, which are then preferably polysaccharides, cellulose derivatives, aminoplasts, polyvinyl alcohols, polyvinylpyrrolidone , polyurethane and/or urea-urethane resins, particularly preferably urea-urethane resins.

Urea urethane resins as thickeners according to component (B) of the preferred process according to the invention for providing colloidal aqueous solutions starting from aqueous dispersions are obtained by reacting polyhydric isocyanates with polyols and mono- and/or diamines. is a mixture of polymeric compounds derived from In a preferred embodiment, the urea urethane resin is preferably 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2(4),4-trimethyl-1,6-hexamethylene diisocyanate, 1,10 -decamethylene diisocyanate, 1,4,-cyclohexylene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate and mixtures thereof, p- and m-xylylene diisocyanate , and 4-4′-diisocyanatodicyclohexylmethane, particularly preferably from 2,4-toluene diisocyanate and/or m-xylylene diisocyanate. In a particularly preferred embodiment, the ureaurethane resin is obtained from a polyol selected from polyoxyalkylenediols, particularly preferably polyoxyethylene glycol, and polyoxyethylene glycol preferably having at least 6, particularly preferably at least 8 more preferably at least 10, but preferably less than 26, particularly preferably less than 23, oxyalkylene units.

Urea urethane resins that are particularly suitable according to the present invention, and therefore preferred, are prepared by first reacting a diisocyanate, such as toluene-2,4-diisocyanate, with a polyol, such as polyethylene glycol, to form an NCO-terminated urethane prepolymer followed by a first It can be obtained by further reaction with primary monoamines and/or primary diamines such as m-xylylenediamine. Urea urethane resins having neither free nor blocked isocyanate groups are particularly preferred. Such urea-urethane resins promote the formation of loose aggregates of primary particles, as constituents of the aqueous dispersions from which the aqueous colloidal solutions of the process according to the invention can be obtained by dilution, which in the aqueous phase stabilized and protected from further agglomeration to the extent that sedimentation of the particulate component in the aqueous dispersion is largely prevented. To further enhance this property profile, urea-urethane resins having neither free or blocked isocyanate groups nor terminal amine groups are preferably used as component (B). Therefore, in a preferred embodiment, the thickening agent by component (B), which is a urea urethane resin, is in each case less than 8 mg KOH/g, in particular It preferably has an amine number of less than 5 mg KOH/g, particularly more preferably less than 2 mg KOH/g. Since the thickener is substantially dissolved in the aqueous phase, it can be assigned to the non-particulate constituents of the aqueous dispersion and component (A2) is substantially bound to the particulate constituent (A). but the totality of the macromolecular organic compounds in the non-particulate component preferably has an amine number of less than 16 mg KOH/g, particularly preferably less than 10 mg KOH/g, particularly more preferably less than 4 mg KOH/g. Aqueous dispersions are preferred for providing colloidal aqueous solutions of the same. The urea-urethane resins have a hydroxyl number in the range from 10 to 100 mg KOH/g, particularly preferably in the range from 20 to 60 mg KOH/g, determined according to Method A of European Pharmacopoeia 9.0 01/2008:20503. is more preferred. In terms of molecular weight, weight-average molar masses of the ureaurethane resins in the range from 1000 to 10000 g/mol, preferably in the range from 2000 to 6000 g/mol are advantageous according to the invention and therefore in each case according to the invention. It is preferably determined experimentally, as described above in connection with the definition of macromolecular compounds.

Without the addition of adjuvants, the pH of the dispersion for providing the aqueous colloidal solution for activation of the process according to the invention is usually in the range of 6.0 to 9.0, so such a pH range is the present invention. Preferred according to the invention. However, for compatibility with practically common aqueous alkaline colloid solutions in the activation stage, the addition of compounds that react in an alkaline manner results in the pH of the aqueous dispersion optionally exceeding 7.2, especially Advantageously, it is preferably greater than 8.0. The alkalinity of the aqueous dispersions according to the invention is ideally limited, since some polyvalent metal cations have amphoteric properties and can therefore be desorbed from the particulate component at higher pH values, As a result, the pH of the aqueous dispersion is preferably below 10, particularly preferably below 9.0.

The aqueous dispersions described above for providing colloidal aqueous solutions preferably include, as part thereof,
i) 10 parts by weight of inorganic particulate compound (A1) are triturated with 0.5 to 2 parts by weight of macromolecular organic compound (A2) in the presence of 4 to 7 parts by weight of water, for example Zetasizer® ) providing a pigment paste by Nano ZS, Malvern Panalytical GmbH, by 1000-fold dilution with water followed by grinding to reach a D50 value of less than 1 μm as determined by dynamic light scattering;
ii) comprising at least 5% by weight of the dispersed particulate component (A) and a maximum kinematic viscosity of at least 1000 Pa·s at a temperature of 25° C. in a shear rate range of 0.001 to 0.25 per second; and ⁱⁱⁱ ) with an alkaline reacting compound to a pH of 7 can be obtained by setting the range from .2 to 10.0,
A preferred embodiment of the dispersion is the corresponding components (A1), (A2) and (A2) and ( It is similarly obtained by choosing A).

The aqueous dispersions may also contain adjuvants, for example selected from preservatives, wetting agents and antifoam agents, contained in amounts necessary for the relevant function. The content of auxiliaries, particularly preferably other compounds, in the non-particulate component which are neither thickeners nor compounds which react in an alkaline manner is preferably less than 1% by weight. In the context of the present invention, compounds that react in an alkaline fashion are water soluble (water solubility: at least 10 g/kg water with κ<1 μScm ⁻¹ ) and have a pK _B value greater than 8.0 for the first protonation step. .

All materials containing more than 50 wt. Anticorrosion pretreatments always relate to the surface of materials or components. The material can be a uniform material or coating. According to the invention, the galvanized steel grades consist of both material steel and material zinc, allowing the iron surface to be exposed at the cutting edges and cylindrical grinding points of e.g. car bodies made of galvanized steel. Yes, in which case, according to the invention, there is a pretreatment of the material iron.

Components to be treated according to the present invention are tertiary of any shape and design resulting from the manufacturing process, including in particular semi-finished products such as strips, metal sheets, rods, pipes, etc., and also composite structures assembled from such semi-finished products. Pre-construction or semi-finished products are preferably interconnected by gluing, welding and/or flanging to form a composite structure.

There may be a rinsing step between activation (i) and phosphating (ii) to reduce carry-over of the predominantly acidic alkaline constituents into the phosphating treatment, although activation Preferably, the rinsing step is omitted to maintain full performance. The rinsing step completely removes soluble residues, particles and active ingredients carried over from the treated ingredients by adhering to the ingredients from previous wet chemical treatment steps, without metallic or semi-metallic active ingredients. used only for full or partial removal, the metallic or semi-metallic element-based active ingredient is already consumed simply by contacting the metallic surface of the ingredient with the rinse liquor and is contained in the rinse liquor itself. For example, the rinse solution may simply be tap water or deionized water, or optionally a rinse solution containing a surface-active compound to improve wetting by the rinse solution.

For the purpose of layer-forming phosphating, which is the purpose of the activation of the metallic material and the formation of a semi-crystalline coating, the phosphating in process step ₍ ii) consists of phosphate dissolved in water, calculated as PO It is preferably done by contacting the surface with an acidic aqueous composition containing from 5 to 50 g/kg and preferably further containing at least one source of free fluoride. According to the invention, the amount of phosphate ions comprises orthophosphoric acid and the anions of salts of orthophosphoric acid dissolved in water, calculated as _PO4 .

In a preferred embodiment of the invention the subsequent phosphating is a zinc phosphating and the phosphating in process step (ii) comprises an acidic aqueous composition containing 0.3-3 g/kg of zinc ions. based on an acidic aqueous composition containing phosphate ions, preferably 5-50 g/L, zinc ions 0.3-3 g/L and an amount of free fluoride.

A source of free fluoride ions is desired to form a layer on any metallic material selected from zinc, iron or aluminum, e.g. required for zinc phosphating of automobile bodies, which are also made at least partially of aluminum. is integral to the process of layer-forming zinc phosphating. If all surfaces of the component metal material are provided with a phosphate coating, the amount of particulate constituents in the activation should be matched to the amount of free fluoride required for layer formation in the zinc phosphating. I often have to. In the process according to the invention based on activation (i) followed by zinc phosphating (ii), in which the components to be pretreated are made from metallic materials of zinc and iron, in particular steel, free Advantageously, the amount of closed, defect-free phosphate coating relative to the amount of fluoride is at least 0.5 mmol/kg. If the component is also made of the metallic material aluminium, and if its surface is also provided with a closed phosphate coating, then in the process according to the invention the amount of free fluoride in the acidic aqueous composition is at least 2 mmol. /kg is also preferred. The concentration of free fluoride should not exceed the value at which the phosphate coating has predominantly readily wipeable adhesion, since these adhesions are due to the particulate constituents in the aqueous colloidal solution of the activation. This is because it is not possible to avoid a disproportionate increase in the amount of Therefore, in the process according to the invention based on activation (i) followed by zinc phosphating (ii), the concentration of free fluoride in the acidic aqueous composition of the zinc phosphating is less than 15 mmol/kg, particularly preferably 10 mmol It is also economically advantageous and therefore preferred to be below 8 mmol/kg, particularly more preferably below 8 mmol/kg.

The amount of free fluoride can be determined potentiometrically with a fluoride-sensitive measuring electrode at 20° C. in a relevant acidic aqueous composition after calibration with a fluoride-containing buffer without pH buffering. Suitable sources of free fluoride are hydrofluoric acid and its water-soluble salts, such as ammonium difluoride and sodium fluoride, and complex fluorides of the elements Zr, Ti and/or Si, especially complex fluorides of the element Si. be. Therefore, in the phosphating process according to the invention, the source of free fluoride is preferably selected from hydrofluoric acid and its water-soluble salts and/or complex fluorides of the elements Zr, Ti and/or Si . A salt of hydrofluoric acid is water-soluble within the meaning of the invention if its solubility in deionized water at 60° C. (κ<1 μScm ⁻¹ ), calculated as F, is at least 1 g/L. be.

Such a method according to the invention in which a zinc phosphating treatment is performed in step (ii) to suppress what is known as "pin-holing" on the surface of metallic materials made of zinc. In the method it is preferred that the free fluoride source is at least partially selected from complex fluorides of the element Si, in particular hexafluorosilicic acid and its salts. The term pinholing is used by those skilled in the art of phosphating to describe amorphous white in a treated zinc surface or other crystalline phosphate layer on a treated galvanized or alloy-galvanized steel surface. It is understood to mean the phenomenon of local deposition of zinc phosphate. Pinholing is caused in this case by the locally increased acid cleaning rate of the substrate. Pinholes should be largely avoided in practice, as such point defects in phosphating can initiate corrosive delamination of subsequently applied organic coating systems. . In this context, the concentration of silicon in water-soluble form in the acidic aqueous composition of zinc phosphating in process step (ii) is at least 0.5 mmol/kg, particularly preferably at least 1 mmol/kg, particularly preferably at least 1 mmol/kg. is at least 2 mmol/kg, but preferably less than 15 mmol/kg, particularly preferably less than 12 mmol/kg, particularly more preferably less than 10 mmol/kg, very preferably less than 8 mmol/kg. The upper limit of the concentration of silicon, above these values, is mostly avoided by favoring phosphate coatings with loose adhesion, even by disproportionately high amounts of particulate constituents in the aqueous colloidal solution of the activation stage. preferred because it cannot The concentration of silicon in the acidic aqueous composition in water dissolved form was determined by atomic emission spectroscopy (ICP-OES) in the filtrate of membrane filtration of the acidic aqueous composition performed using a membrane with a nominal pore size of 0.2 μm. can be determined by

With respect to the interaction of activation with zinc phosphating, the content of particulate constituents that contribute to the activation is the layering phosphate relative to the component containing aluminum as the metallic material contained in the phosphating bath. It may be necessary to adapt the amounts of free fluoride and silicon during zinc phosphating to ensure that higher amounts of free fluoride for the salt treatment do not adversely affect layer formation. As can be seen, this is very important for a consistent quality of the phosphate coating, especially when pretreating a large number of components. In this connection, preference is given to a method according to the invention in which a series of components is pretreated, said series of components comprising components made at least partially of zinc and aluminum materials, the series of components comprising a continuous in a method step of first undergoing activation (i) and then zinc phosphating (ii), the activation in method step (i) being effected by contacting the component with an aqueous colloidal solution as described above, which is obtainable, in a preferred embodiment, as a 20 to 100,000-fold diluted aqueous dispersion as described above, and the zinc phosphate treatment in process step (ii) is
(a) 5 to 50 g/l of phosphate ions,
(b) 0.3 to 3 g/l of zinc ions, and (c) at least one free fluoride source, by contact with an acidic aqueous composition,
Concentration of phosphate in the inorganic particulate constituent of the colloidal aqueous solution of the activation, based on PO ₄ , relative to the sum of the free fluoride concentration and the silicon concentration in each case in the acidic aqueous zinc phosphating composition quotient (mmol/kg) is in each case greater than 0.2, preferably greater than 0.3 and particularly preferably greater than 0.4.

As far as the zinc phosphating treatment in process step (ii) is mentioned in the context of the second aspect of the invention, the preferred pH of the acidic aqueous composition that provides the zinc phosphating treatment is above 2.5, particularly preferably 2 .7, but preferably less than 3.5, particularly preferably less than 3.3. The free acid content at points in the acidic aqueous composition of the zinc phosphating treatment in process step (ii) is preferably at least 0.4, but preferably no more than 3.0, particularly preferably no more than 2.0. is. The content of free acid at points is determined by diluting a 10 ml sample volume of the acidic aqueous composition to 50 ml and titrating to pH 3.6 with 0.1 N sodium hydroxide solution. Consumption of sodium hydroxide solution in mL indicates the number of free acid points.

Conventional addition of additives for zinc phosphating is such that the acidic aqueous composition of process step (ii) contains hydrogen peroxide, nitrite, hydroxylamine, nitroguanidine and/or N-methylmorpholine-N-oxide. as well as manganese metal, calcium and/or iron cations in the form of water-soluble salts that have a positive effect on layer formation. can also For environmental hygiene reasons, in a preferred embodiment, a total of less than 10 ppm nickel and/or cobalt ions are contained in the acidic aqueous composition of the zinc phosphating treatment in process step (ii).

The method according to the invention produces a good coating primer for the subsequent dip coating in the course of which the substantially organic cover layer is applied. Therefore, in a preferred embodiment of the method according to the invention, the zinc phosphating treatment with or without an intermediate rinsing and/or drying step, or preferably with a rinsing step but without a drying step, is followed by dip coating, particularly preferably is electrocoated, more preferably cathodic electrocoated, which preferably contains water-soluble or water-dispersible salts of yttrium and/or bismuth in addition to a dispersing resin comprising an amine-modified polyepoxide. preferable.

Below, the properties of the additive-free, i.e. condensed phosphate-free, activation are evaluated both as a bath life and as a result of the phosphate layer weight and corrosion protection achieved with subsequent zinc phosphate treatment. is shown with respect to

<Preparation of pigment paste>
To prepare a pigment paste for obtaining an activating dispersion, 15 parts by weight of Edaplan® 490 (Muenzing Chemie GmbH) as a dispersing agent are added to 25 parts by weight of fully deionized water (κ<1 μScm ⁻¹ ). and then mixed with 60 parts by weight of zinc phosphate of quality level PZ 20. This phase was transferred to a KDL type Dyno®-Mill bead mill and the zinc phosphate particles were continuously milled for 2 hours (milling parameters: 75% bead loading level, 2000 rpm, 20 L volumetric flow rate/hour, milled material temperature 40-45°C). The result was an average particle size of about 0.35 μm as determined using a Zetasizer Nano ZS from Malvern.

<Preparation of dispersion for activation>
Then, resins based on amine-modified prepolymers of TDI/XDI and PEG ^- 16 (amine value <1 mg KOH/g; hydroxyl value about 40 mg KOH 2.5 parts by weight of a urea-urethane resin solution containing 40 wt. About 33 parts by weight of pigment paste were then added with stirring, adjusted to pH 9 using 1% by weight NaOH solution and stirred until complete homogenization.

<Preparation of colloid aqueous solution for activation for zinc phosphate treatment>
5 liters of A) fully deionized water (κ<1 μScm ⁻¹ ) or B) fully deionized water containing 5 grams of an additive solution consisting of 10.3 wt % potassium pyrophosphate and 25.3 wt % potassium phosphate. Ionized water (κ<1 μScm ⁻¹ ) was prepared in a 5 L beaker, brought to pH 10.5 with phosphoric acid while stirring, and 7.5 grams of the above dispersion was added. The pH was then adjusted to 10.5 using 1% sodium hydroxide solution while stirring.

<Method sequence of zinc phosphate treatment>
Cold-rolled steel (CRS), hot-dip galvanized steel (HDG) and aluminum (AA6014) plates for stratified phosphating with activation based on aqueous colloidal solutions were as follows:
a) First, 4 in a degreasing bath containing 4 wt. Alkaline washing with stirring in Düsseldorf city tap water (pH: 10.2-10.9; 55° C.) by immersion for minutes;
b) subject to rinsing with Düsseldorf city tap water and then fully deionized water (κ<1 μScm ⁻¹ ) for approximately 30 seconds in each case;
c) while wet with water, contacted with an activating solution A according to the invention or with an activating solution B containing additives by immersion for 60 seconds;
d) immediately followed by 4.6% by weight of Bonderite® M-ZN 1994 in fully demineralized water (κ<1 μScm ⁻¹ ) with stirring at 52° C. for 3 minutes without further rinsing steps , 0.8% by weight Bonderite® M-AD 565, 0.24% by weight Bonderite® M-AD 338, and 0.38% by weight Bonderite® M-AD 110 ( Free acid content from 0.9 to 1.4 points (titrated to pH 3.6), Total acid content from 25 to 30 points (titrated to pH 8.5), and a hydroxylamine-promoted phosphating bath having a free fluoride content of about 150 mg/kg;
e) subjected to a rinse of about 30 seconds with fully deionized water (κ<1 μScm ⁻¹ );
f) An approximately 20 μm thick layer of Cathoguard® type 800 (BASF SE) electrocoat was applied and then cured at 180° C. for 35 minutes.

Table 1 summarizes the results of the layer weight and zinc phosphate treatments after aging in the corrosion test. Compared to the approach (B) with the addition of the corresponding additive, activation in the absence of the condensed phosphate (A) resulted in significantly lower layer weights on the CRS and no corrosion on this substrate. A zinc phosphate coating with improved protective results is achieved, but the application of the layer on zinc and aluminum is not adversely affected by the lack of additives and can also provide a homogeneous and closed zinc phosphate coating. can. Only with aluminium, the Filiform test results are slightly lower compared to activation with additives, but nevertheless in many cases the corrosion values normally required in the automotive industry are met. Remarkably, even in the absence of condensed phosphate, the activation performance in the method according to the invention is retained for several months.

Claims (16)

Method for the anti-corrosion pretreatment of a metallic material selected from zinc, iron or aluminum or a component at least partially composed of such a metallic material, said metallic material or said component being subjected to successive method steps first undergoing activation (i) and then phosphating (ii), in particular zinc phosphating, said activation in process step (i) bringing said metallic material or said component into contact with an aqueous colloidal solution. wherein said aqueous colloidal solution is added to a solution of dispersed particulate component (a),
(a1) at least one particulate inorganic compound composed of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and/or hallolite, and (a2) at least partially at least one polymer composed of styrene and/or α-olefins having up to 5 carbon atoms in the nucleus, partly composed of maleic acid, its anhydrides and/or its imides, and further comprising polyoxyalkylene units contains organic compounds,
In said colloidal aqueous solution, the content of condensed phosphate dissolved in water is less than 0.25, in each case based on the phosphate content of said at least one particulate compound based on element P ,Method. In said aqueous colloidal solution, the content of condensed phosphates dissolved in water, based on the phosphate content of said at least one particulate compound, in each case based on element P, is preferably less than 0.20 is less than 0.15, particularly preferably less than 0.10. The content of condensed phosphate dissolved in water, calculated as P, in said aqueous colloidal solution is less than 20 mg/kg, preferably less than 15 mg/kg, particularly preferably less than 10 mg/kg, based on said aqueous colloidal solution 3. A method according to claim 1 or 2, characterized in that Said colloidal aqueous solution contains at least 0.5 mmol/L, preferably at least 1.0 mmol/L, particularly preferably at least 1.5 mmol/L but not more than 10 mmol/L alkaline earth metal ions dissolved in water The method according to any one of claims 1 to 3, characterized in that Said aqueous colloidal solution is preferably selected from α-hydroxycarboxylic acids, then preferably selected from gluconic acid, tartronic acid, glycolic acid, citric acid, tartaric acid, lactic acid, very preferably gluconic acid and/or organic phosphonic acids. and then preferably etidronic acid, aminotris(methylenephosphonic acid), aminotris(methylenephosphonic acid), phosphonobutane-1,2,4-tricarboxylic acid, diethylenetriaminepenta(methylenephosphonic acid), hexamethylenediaminetetra(methylenephosphonic acid ) and/or hydroxyphosphonoacetic acid, particularly preferably etidronic acid. The amount of the complexing agent in the colloidal aqueous solution is 2 times or less the molar amount of the alkaline earth metal ion, preferably 1.5 times or less, and particularly preferably equal to or less than the molar amount of the alkaline earth metal ion. 6. A method according to claim 5, characterized in that: characterized in that said colloidal aqueous solution in activation (i) has an alkaline pH, preferably above 8.0, particularly preferably above 9.0, but preferably below 11.0, The method according to any one of claims 1-6. The content of phosphate, calculated as PO4, contained in said at least one particulate inorganic compound ₍ a1), based on said dispersed inorganic particulate constituents of said aqueous colloidal solution, is preferably at least 25 % by weight, particularly preferably at least 35% by weight, particularly more preferably at least 40% by weight, very preferably at least 45% by weight. The polymeric organic compound (a2) in the colloidal aqueous solution contains polyoxyalkylene units in their side chains, and the content of the polyoxyalkylene units in the entire polymeric organic compound (a2) is preferably at least 9. Process according to any of the preceding claims, characterized in that it is 40% by weight, particularly preferably at least 50% by weight, but particularly preferably not exceeding 70% by weight. The organic polymer compound (a2) of the colloidal aqueous solution is preferably composed of pyridine, imidazole, imidazoline, morpholine, pyrrole and/or pyrrolidone units, particularly preferably imidazole and/or imidazoline units, particularly more preferably imidazole units. selected, each preferably part of a side chain of said macromolecular organic compound (a2), within the side chain and then preferably via at least 3 carbon atoms, particularly preferably said macromolecular It also contains N-heterocyclic units that are aliphatically connected to the main chain in such a way that the polyoxyalkylene units of the organic compound (a2) are at least partially endcapped with N-heterocyclic units. A method according to any one of claims 1 to 9, characterized in that The aqueous colloidal solution is preferably selected from urea-urethane resins, preferably urea-urethane resins having an amine number of less than 8 mg KOH/g, particularly preferably less than 5 mg KOH/g, very preferably less than 2 mg KOH/g. Process according to any of the preceding claims, characterized in that it contains one thickening agent as further component b). the total macromolecular organic compound in and based on said particulate constituents of said aqueous colloidal solution is at least 3% by weight, preferably at least 6% by weight, but preferably does not exceed 15% by weight; The method according to any one of claims 1 to 11, characterized in that Process according to any of the preceding claims, characterized in that the aqueous colloidal solution has a D50 value of less than 1 µm, preferably less than 0.4 µm. The content of said particulate constituents of said aqueous colloidal solution is in each case based on said aqueous colloidal solution is at least 0.05 g/kg, preferably at least 0.1 g/kg, particularly preferably at least 0.2 g/kg but preferably not more than 10 g/kg, particularly preferably not more than 2 g/kg. The colloidal aqueous solution is obtained as an aqueous dispersion diluted 20 to 100,000 times,
- at least 5% by weight of dispersed particulate component (A), based on said aqueous dispersion,
(A1) at least one particulate inorganic compound composed of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and/or hallolite;
(A2) at least partially composed of styrene and/or α-olefins having 5 or less carbon atoms, at least partially composed of maleic acid, its anhydrides and/or its imides, containing polyoxyalkylene units a dispersed particulate component (A), which further comprises at least one high molecular weight organic compound; Process according to any of the preceding claims, characterized in that it comprises at least one thickening agent selected from urea-urethane resins, particularly preferably with an amine number of less than 2 mg KOH/g. The phosphating in process step (ii) comprises 5-50 g/kg phosphate dissolved in water calculated as PO4, 0.3-3 g/kg zinc ions and a _total of 0.1 g/kg A process according to any of the preceding claims, characterized in that it is carried out by contact with an acidic aqueous composition containing an amount of free fluoride which may contain less than kg of ions of elemental nickel and elemental cobalt. .