Resource-saving method for zinc phosphate treatment of metal surfaces

Abstract

The present invention relates to a method for zinc phosphate treatment of metal surfaces in a layer forming process using an aqueous colloidal solution as an activation step, wherein in a method step following activation, 2.0 g / m 2 The present invention relates to a method for depositing a zinc phosphate layer having a layer weight of less than 10 ...

Description

[Technical Field]

[0001] The present invention relates to a method for zinc phosphate treatment of metal surfaces in a layer forming process using an aqueous colloidal solution as an activation step, wherein in a method step following activation, 2.0 g / m 2 The present invention relates to a method for depositing a zinc phosphate layer having a layer weight of less than 10 ... [Background technology]

[0002] Layer-forming phosphating is a method for applying crystalline anticorrosive coatings to metal surfaces, particularly iron, zinc, and aluminum, that has been used and extensively studied for decades. Zinc phosphating, a particularly well-established method for corrosion protection, is performed in layers several micrometers thick and is based on the corrosive pickling of metal materials in an acidic aqueous composition containing zinc ions and phosphate. During the pickling process, an alkali diffusion layer forms on the metal surface, which extends into the solution, forming sparingly soluble crystallites within. These crystallites precipitate directly at the interface with the metal material, where they continue to grow. Water-soluble compounds that are a source of fluoride ions are often added to support the pickling reaction on the aluminum metal material and to mask the aluminum bath poison, which in dissolved form interferes with layer formation on the metal material. By default, for good corrosion protection and coating integrity, zinc phosphating requires a concentration of at least 2 g / m, especially on the zinc surface of the component.2 The acid pickling and zinc phosphating steps are designed to achieve a closed crystalline coating at a layer weight of 0.01g. The concentrations of the active ingredients in the acid pickling and zinc phosphating steps must be adjusted accordingly depending on the metal surface to be phosphated, in order to ensure a correspondingly high layer weight on the surfaces of metallic iron or steel, zinc, and aluminum. Zinc phosphating always begins with the activation of the metal surface of the component to be phosphated. Wet-chemical activation is conventionally carried out by contact with an aqueous colloidal solution of phosphate (the "activation step"); the phosphate, as long as it remains immobilized on the metal surface, serves as a growth nucleus for the formation of a crystalline coating within the alkali diffusion layer in the subsequent phosphating step. Suitable dispersions in this case are colloidal, mostly neutral to alkaline, aqueous compositions based on phosphate crystallites, which have only slight crystallographic deviations in their crystal structure from the type of zinc phosphate layer to be deposited. In this regard, WO 98 / 39498 teaches divalent and trivalent phosphates of the metals Zn, Fe, Mn, Ni, Co, Ca and Al, among others, and it is technically preferred that the phosphate of the metal zinc be used for activation for the subsequent zinc phosphating treatment.

[0003] Activation steps based on the dispersion of divalent and trivalent phosphate salts require a high level of process control to maintain optimal activation performance, especially when treating a series of metal components. To ensure a sufficiently robust process, foreign ions carried over from previous treatment baths or aging processes of the aqueous colloidal solution must not degrade activation performance. Degradation first becomes apparent in an increase in layer weight in subsequent phosphating treatments, ultimately resulting in the formation of defective or uneven phosphate layers. Therefore, zinc phosphating treatments with layer formation as a whole are technically complex to control and have traditionally been carried out in a resource-intensive manner, both in terms of process chemicals and energy consumed. This is particularly true for the zinc phosphating process step, which initially requires high material requirements due to layer formation, especially on components with zinc surfaces, but also results in significant material removal into the phosphating bath in a manner related to the required pickling rate. High pickling rates result in measures having to be taken to prevent or control and dispose of phosphate sludge, thereby necessitating the use of additional process chemicals. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Application Publication No. 98 / 39498 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a need to optimize pretreatment lines for zinc phosphating, including activation and phosphating steps, so that the overall process can be carried out in a less resource-intensive manner, especially in the pretreatment of components with zinc surfaces. However, this resource-saving overall process must not come at the expense of the properties of the zinc phosphating, which must be provided as a homogeneous, closed coating with high charge transfer resistance in the subsequent electrocoating to allow good protection against corrosion and correspondingly good coverage. [Means for solving the problem]

[0006] This complex task profile can surprisingly be achieved by the deposition of a relatively thin phosphate coating, and activation with specific polymeric dispersants to stabilize the colloidal component of the particulate phosphate-based activation step is necessary as long as it is guaranteed that a minimum amount of particulate component is not lacking in the activation step. Due to the highly effective stabilization of the particulate component that results in activation, the specific dispersants can also ensure the establishment of a high proportion of colloids in the quasi-continuous process of zinc phosphating, which surprisingly leads to improved activation of the metal surface and the formation of a particularly thin, yet homogeneous and closed phosphate coating with high electro-osmotic resistance.

[0007] The present invention therefore relates to a method for the anticorrosive pretreatment of a metallic material having at least partly a surface composed of zinc or of such a metallic material, in which said metallic material or said component is subjected in successive method steps first to an activation (i) and then to a phosphating treatment (ii), said activation in method step (i) being carried out by contacting said metallic material or said component with an aqueous colloidal solution, said aqueous colloidal solution containing, in its dispersed particulate component (a), (a1) at least one particulate inorganic compound composed of a phosphate salt of a polyvalent metal cation selected at least in part from hopeite, phosphophyllite, scholzite, and / or hallolite; and (a2) at least one polymeric organic compound composed at least in part of styrene and / or an α-olefin having 5 or fewer carbon atoms, further comprising units of maleic acid, its anhydride and / or its imide, and further comprising polyoxyalkylene units; Including, The content of particulate components in the aqueous colloidal solution is at least 4 g / kg based on the aqueous colloidal solution; and In process step (ii), 2.0 g / m 2 A zinc phosphate layer having a layer weight of less than 1000 .mu.m is deposited on the surface of the zinc.

[0008] In the context of the method according to the invention, a metallic material has at least one surface consisting of zinc if, to a material penetration depth of at least 1 micrometer, more than 50 atomic % of the metallic structure on this surface consists of zinc. This usually applies to metallic materials in which 50 atomic % or more of the metallic material consists of zinc as a homogeneous material, but also to materials provided with a metallic coating of zinc, such as electrogalvanized or hot-dip galvanized steel sheets, which may be alloyed with iron (ZF), aluminum (ZA) and / or magnesium (ZM).

[0009] The components treated according to the invention can be three-dimensional structures of any shape and design resulting from a manufacturing process, including in particular semi-finished products such as strips, sheets, rods, pipes, etc., as well as composite structures assembled from said semi-finished products, which are preferably joined together by gluing, welding and / or flanging to form the composite structure. DETAILED DESCRIPTION OF THE INVENTION

[0010] The dispersed particulate component (a) of the aqueous colloidal solution in activation (i) of the method according to the invention is the solids remaining after drying the retentate of the ultrafiltration of a defined partial volume of an aqueous dispersion having a nominal cut-off limit of 10 kD (NMWC: nominal molecular weight cut-off). The ultrafiltration is carried out at a concentration of 10 μS cm in the filtrate. -1 Deionized water until a conductivity of less than κ<1 μS cm is measured -1) is added.

[0011] 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. The molar mass is determined using the molar mass distribution curve of a sample of relevant reference values, which is experimentally established at 30°C by size exclusion chromatography using a concentration-dependent refractive index detector and calibrated against polyethylene glycol standards. The average molar mass is evaluated using a computer according to the strip method with a third-order calibration curve. Hydroxylated polymethacrylate is preferred as the column material, and an aqueous solution of 0.2 mol / L sodium chloride, 0.02 mol / L sodium hydroxide, and 6.5 mmol / L ammonium hydroxide is preferred as the eluent.

[0012] The method according to the invention is characterized in that, when the amount of particulate components in the aqueous colloidal solution exceeds 4 g / kg, a homogeneous and closed zinc phosphate coating is already grown on the surface of the metal material at very low layer weights, which surface represents a coating substrate for subsequent electrocoating equivalent to prior art zinc phosphate coatings, while at the same time providing excellent coverage. Nevertheless, the invention aims at depositing a homogeneous and closed zinc phosphate coating on the zinc surface, for which reason, according to the invention, in method step (ii) a coating of 0.5 g / m 2 More than 1.0 g / m 2 It is envisaged that a zinc phosphate coating having a layer weight of greater than 1000 mg / m² is provided on the zinc surface.

[0013] A reduction in bed weight also allows for shorter wet chemical exposure times or contact times with the acidic aqueous zinc phosphate composition, which in turn correlates with both lower acid wash removal and shorter overall pretreatment periods. Further increases in the content of particulate components in the aqueous colloidal solution allow for further reductions in bed weight or contact time in the zinc phosphate treatment, so the method of the present invention is preferred in which the content of particulate components in the aqueous colloidal solution is at least 6 g / kg, particularly preferably at least 8 g / kg, and more particularly preferably at least 10 g / kg. However, the achievable reduction in bed weight in the zinc phosphate treatment with further increases in colloid content in the activation stage is only slight, and increasingly conflicts with drawbacks in process control and lower colloid stability in the activation stage. Therefore, it is preferred to limit the content of particulate components in the aqueous colloidal dispersion to 20 g / kg, particularly preferably to 15 g / kg, in each case based on the aqueous colloidal solution.

[0014] In the method according to the present invention, for the resource-saving operation of the pretreatment line, the layer coating of zinc phosphate on the zinc surface is 2.0 g / m 2 It is desirable to limit the layer weight of zinc phosphate on the zinc surface to 1.8 g / m2 in process step (ii). According to the invention, a minimum amount of particulate components in the colloidal aqueous dispersion of the activation step provides a sufficiently homogeneous and closed zinc phosphate coating with excellent coverage behavior in the subsequent electrocoating. The activation of the zinc surface is effective in process step (i) of the process according to the invention in such a way that a further reduction in the layer coating and therefore in the material consumption in the zinc phosphating step in process step (ii) is possible. Therefore, in process step (ii), the layer weight of zinc phosphate on the zinc surface is limited to 1.8 g / m2. 2 less than 1.6 g / m 2 less than 1.5 g / m 2It is preferred to limit the layer weight to less than 1000 kJ / cm. Limiting the layer weight can be achieved by process control either by shortening the contact time with the acidic aqueous composition for zinc phosphating in process step (ii) and / or by increasing the particulate content of the colloidal aqueous dispersion in process step (i). The zinc phosphate layer weight can be reduced by removing the zinc phosphate layer using a 5 wt. % aqueous CrO3 solution as an acid pickle which is contacted with the predefined areas of the phosphating material or component for 5 minutes at 25°C immediately after the zinc phosphating treatment, and by using deionized water (κ<1 μS cm -1 ) and subsequently measuring the phosphorus content in the same pickling solution using ICP-OES. The zinc phosphate layer weight is determined by multiplying the amount of phosphorus relative to the surface area by a factor of 6.23.

[0015] A further particular advantage of the method according to the invention is that in process step (i) in addition to the zinc surface, the iron and aluminum surfaces are also activated very effectively, and in process step (ii) a very homogeneous, closed zinc phosphate coating is accessible on said surfaces, which likewise has a relatively low layer weight. Thus, according to the invention, components which in addition to the zinc surface also have iron and / or aluminum surfaces are preferably treated, and in process step (ii) a zinc phosphate coating of 2.0 g / m 2 is applied to the iron and aluminum surfaces. 2 less than 1.8 g / m 2 less than 1.6 g / m 2 less than, very particularly preferably 1.5 g / m 2 less than, but preferably at least 0.5 g / m 2 , particularly preferably at least 1.0 g / m 2 Preferably, a zinc phosphate layer having a layer weight of 0.015 to 0.015 is deposited. Similarly, the metallic material has at least one surface consisting of iron or aluminum, if more than 50 atomic % of the metallic structure on this surface is composed of iron or aluminum, to a material penetration depth of at least 1 micrometer.

[0016] Furthermore, in the context of the present invention, it has been found that the condensed phosphate dissolved in water in the activation step of prior art methods, which is often added for colloid stabilization, is only of secondary importance in maintaining a consistently good phosphate coating in the context of the present invention.It is remarkable and surprising for those skilled in the art that the addition of condensed phosphate can be largely or completely omitted in the process according to the present invention, which is based on an activation step based on particulate component (a) present in an amount of at least 4 g / kg based on the aqueous colloidal solution.In a preferred embodiment of the process according to the present invention, the content of condensed phosphate dissolved in water in the activation step is less than 0.25, particularly preferably less than 0.20, more particularly preferably less than 0.15, and very particularly preferably less than 0.10, based on the phosphate content of at least one particulate compound in the aqueous colloidal solution, in each case based on the element P.

[0017] Furthermore, in this regard, it is preferred that the content of condensed phosphate dissolved in water in the aqueous colloidal solution of the method according to the invention, calculated as P, is less than 100 mg / kg, particularly preferably less than 20 mg / kg, more particularly preferably less than 15 mg / kg, and very particularly preferably less than 10 mg / kg, based on the aqueous colloidal solution. Overall, in the context of the present invention, the addition of condensed phosphate can thereby be completely omitted, and the activation therefore involves only small amounts of condensed phosphate that reach the activation stage from the previous washing stage containing the components to be pretreated, especially when treating a large number of components in succession.

[0018] 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 with monovalent cations, preferably selected from Li, Na and / or K, particularly preferably Na and / or K.

[0019] The content of condensed phosphate can be analytically determined from the difference in the total phosphate content in the non-particulate component of the aqueous colloid solution, with or without oxidative digestion using, for example, peroxodisulfate, while the dissolved orthophosphate content is quantified photometrically. 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 colloid solution is the solids content of the aqueous colloid solution in the permeate of the above-mentioned ultrafiltration after drying to constant mass at 105°C, i.e., the solids content after the particulate component (a) has been separated by ultrafiltration.

[0020] The high tolerance of the method according to the invention to carried-over foreign ions also allows the washing and rinsing steps carried out before the activation step, as well as the activation step itself, to be carried out with tap water instead of deionized water. In this way, the method according to the invention is carried out in a particularly resource-saving manner. Therefore, according to the invention, it is preferred that the aqueous colloidal solution used in the activation step contains at least 0.5 mmol / L, particularly preferably at least 1.0 mmol / L, particularly preferably at least 1.5 mmol / L, but preferably not more than 10 mmol / L, of alkaline earth metal ions dissolved in water.

[0021] If the tolerance of the method according to the invention reaches the system-specific limits in any case with very high ionic strength, e.g. high permanent water hardness, and at the same time a high content of foreign ions carried over from the previous cleaning step, organic complexing agents can be added to mask the foreign ions in order to maintain a long bath life. In this case, it must be evaluated whether the economic advantage of being able to carry out the activation step, and if necessary the preceding cleaning step, and rinse with clean water, is not hindered by the addition of organic complexing agents in the system tank of the activation step and their technical monitoring. Suitable organic complexing agents preferred in this context are selected from α-hydroxycarboxylic acids, which in turn are preferably selected from gluconic acid, tartronic acid, glycolic acid, citric acid, tartaric acid, lactic acid, very particularly preferably gluconic acid, 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, diethylenetriaminepenta(methylenephosphonic acid), hexamethylenediaminetetra(methylenephosphonic acid) and / or hydroxyphosphonoacetic acid, particularly preferably selected from etidronic acid.

[0022] In order to maintain stable activation performance, the organic complexing agent should be added only to the extent that its amount in the aqueous colloidal solution is preferably not more than 2 times the amount of alkaline earth metal ions, particularly preferably not more than 1.5 times, and very particularly preferably not more than equimolar to the amount of alkaline earth metal ions.

[0023] The aqueous colloidal solution in activation (i) of the method 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, and it is possible to use pH-influencing compounds 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 decimal logarithm of the hydronium ion activity at 20°C and can be determined by means of a pH-sensitive glass electrode.

[0024] For good activation performance, a correspondingly high proportion of polyvalent metal cations in the form of phosphate must be included in the dispersed particulate component (a) for activation. Therefore, the phosphate content of the at least one particulate inorganic compound (a1) is preferably at least 25% by weight, particularly preferably at least 35% by weight, particularly more preferably at least 40% by weight, and very particularly preferably at least 45% by weight, based on the dispersed particulate component (a) of the aqueous colloidal solution. The inorganic particulate component of the aqueous colloidal solution is then pyrolyzed in a reactor by supplying a CO₂-free oxygen stream at 900°C without the addition of catalysts or other additives until the infrared sensor provides a signal at the reactor outlet identical to that of a CO₂-free carrier gas (blank value). The phosphate content of the inorganic particulate component is determined directly from the acid digestion by atomic emission spectrometry (ICP-OES) after acid digestion of the component with 10% by weight aqueous HNO₃ solution at 25°C for 15 minutes.

[0025] The active component of the colloidal aqueous dispersion, which effectively promotes the formation of a closed phosphate coating on the metal surface and in this sense activates the metal surface, is, as already mentioned, mainly composed of phosphate, which then leads to the formation of a finely crystalline coating and is therefore at least partially selected from hopeite, phosphophyllite, scholzite and / or hallolite, preferably at least partially selected from hopeite, phosphophyllite and / or scholzite, particularly preferably at least partially selected from hopeite and / or phosphophyllite, very particularly preferably at least partially selected from hopeite. Activation within the meaning of the present invention is therefore essentially based on phosphate in particulate form being included in the activation step. Without taking into account the water of crystallization, hopeite stoichiometrically comprises Zn3(PO4)2 and the nickel- and manganese-containing variants Zn2Mn(PO4)3 and Zn2Ni(PO4)3, while phosphophyllite consists of Zn2Fe(PO4)3, scholzite of Zn2Ca(PO4)3 and hallolite of Mn3(PO4)2. The presence of hopeite, phosphophyllite, scholzite and / or hallolite crystalline phases in the aqueous dispersions according to the invention can be demonstrated by X-ray diffractometry (XRD) after separation of the particulate component (a) by ultrafiltration with a nominal cut-off limit of 10 kD (NMWC: nominal molecular weight cut-off) as described above and drying of the retentate to constant mass at 105°C.

[0026] Since the presence of a phosphate containing zinc ions and having a particular crystallinity is preferred, in order to form a strongly adhering crystalline zinc phosphate coating after successful activation in the method according to the invention, it is preferred that the colloidal aqueous dispersion contains at least 20% by weight, particularly preferably at least 30% by weight, and especially more preferably at least 40% by weight of zinc in the inorganic particulate component of the aqueous colloidal solution, calculated as PO4, based on the phosphate content of the inorganic particulate component.

[0027] However, within the meaning of the present invention, activation is preferably not achieved by a colloidal solution of titanium phosphate, since otherwise the layer-forming zinc phosphate treatment on iron, especially steel, cannot be reliably achieved. Therefore, in a preferred embodiment of the method according to the invention, the content of titanium in the inorganic particulate components 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. In a particularly preferred embodiment, the aqueous colloidal solution of activation step (i) contains a total of less than 10 mg / kg, particularly preferably less than 1 mg / kg, of titanium.

[0028] The activation stage in the method according to the invention is further characterized by its D50 value, above which the activation performance is significantly reduced. 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 indicates the particle size of not more than 50% by volume of the particulate components contained in the aqueous colloidal solution. According to ISO 13320:2009, the D50 value is determined according to the Mie theory by the refractive index n of spherical and scattering particles immediately after the sample is taken from the activation stage. D It can be determined at 20 °C from the volume-weighted cumulative particle size distribution by scattered light analysis using = 1.52 − i · 0.1.

[0029] In the sense of the present invention, the polymeric organic compounds (a2) used as dispersants are composed in part of styrene and / or α-olefins having up to 5 carbon atoms, and maleic acid, its anhydrides and / or its imides, and also contain polyoxyalkylene units. These polymeric organic compounds (a2) provide an extremely high stability of the aqueous colloidal solution during the activation stage of the process according to the invention.

[0030] In this case, the α-olefin is preferably selected from ethene, 1-propene, 1-butene, isobutylene, 1-pentene, 2-methylbut-1-ene and / or 3-methylbut-1-ene, particularly preferably isobutylene. Those skilled in the art will understand that the polymeric organic compound (a2) contains these monomers as structural units in unsaturated form, covalently bonded to each other or to other structural units. Suitable commercially available 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), a maleic acid-styrene copolymer modified with polyethylene glycol, 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) partially composed of styrene are preferred.

[0031] The polymeric organic compound (a2) used as a dispersant is preferably composed of 1,2-ethanediol and / or 1,2-propanediol, and particularly preferably has polyoxyalkylene units composed of both 1,2-ethanediol and 1,2-propanediol. The content of 1,2-propanediol in the total polyoxyalkylene units is preferably at least 15% by weight, and particularly preferably 40% by weight or less, based on the total polyoxyalkylene units. Furthermore, it is preferred that the polymeric organic compound (a2) contains polyoxyalkylene units in its side chains. A content of polyoxyalkylene units in the total polymeric organic compound (a2) of at least 40% by weight, particularly preferably at least 50% by weight, and preferably 70% by weight or less, is advantageous for dispersibility.

[0032] In order to fix the inorganic particulate components and dispersants of the aqueous colloidal solution, which are formed at least in part by polyvalent metal cations in the form of phosphates selected from hopeite, phosphophyllite, scholzite and / or hallite, the polymeric organic compound (a2) also contains imidazole units, preferably in such a way that the polyoxyalkylene units of the polymeric organic compound (a2) are at least in part end-capped with imidazole groups; thus, in a preferred embodiment, the terminal imidazole groups are present in the polyoxyalkylene side chains, the covalent bond between the polyoxyalkylene units and the imidazole groups being preferably via a nitrogen atom of the heterocycle.

[0033] 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 less than 80 mg KOH / g. Accordingly, in a preferred embodiment, the total polymeric 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—organic polymeric compound (a2) or the total polymeric organic compounds in the particulate component—in 100 mL of ethanol, and titration is carried out using 0.1 N HCl titrant solution against the indicator bromophenol blue until the color changes to yellow at a temperature of the ethanol solution of 20° C. The amount of HCl titrant solution used in milliliters, multiplied by the coefficient 5.61 and divided by the exact mass in grams, corresponds to the amine value in milligrams of KOH per gram of the relevant reference value.

[0034] The presence of maleic acid in the organic polymeric compound (a2) as a free acid, rather than in its anhydrous or imide form, can increase the dispersant's water solubility, especially in the alkaline range. Therefore, to ensure a sufficient number of polyoxyalkylene units, the polymeric organic compound (a2), preferably the entire polymeric organic compound in the particulate component (a), preferably has an acid value of at least 25 mg KOH / g, preferably less than 100 mg KOH / g, and particularly preferably less than 70 mg KOH / g, according to DGF CV 2(06) (as of April 2018). It is also preferred that the polymeric organic compound (a2), preferably the entire polymeric organic compound in the particulate component (a), have a hydroxyl value of less than 15 mg KOH / g, particularly preferably less than 12 mg KOH / g, and particularly preferably less than 10 mg KOH / g, in each case determined according to Method A of European Pharmacopoeia 9.0 01 / 2008:20503.

[0035] In order to disperse the inorganic particulate component sufficiently in the colloidal aqueous dispersion, it is sufficient for the content of the polymeric organic compound (a2), preferably the total of the polymeric organic compounds in the particulate component (a) based on the particulate component (a), to be at least 3% by weight, particularly preferably at least 6% by weight, but preferably not exceeding 15% by weight.

[0036] In a preferred embodiment, the present invention relates to a method for anticorrosion pretreatment comprising an aqueous dispersion, in such a preferred method according to the invention, the aqueous colloidal solution in method step (i) is obtained as a 20 to 100,000 times diluted aqueous dispersion, said aqueous colloidal solution comprising: - at least 5% by weight, based on said aqueous dispersion, of dispersed particulate component (A), (A1) at least one particulate inorganic compound composed of a phosphate salt of a polyvalent metal cation selected at least in part from hopeite, phosphophyllite, scholzite and / or hallolite; (A2) At least one polymeric organic compound composed at least in part of styrene and / or an α-olefin having 5 or less carbon atoms, further comprising units of maleic acid, its anhydride and / or its imide, and further comprising polyoxyalkylene units. a dispersed particulate component (A) comprising, in order, optionally at least one thickener (B), preferably chosen from urea-urethane resins, particularly preferably urea-urethane resins having an amine value of less than 8 mg KOH / g, preferably less than 5 mg KOH / g, particularly preferably less than 2 mg KOH / g; Includes:

[0037] For the dispersed particulate component (A) and at least one particulate inorganic compound (A1) and polymeric organic compound (A2), the same definitions and preferred specifications apply as given above for the aqueous colloidal solution.

[0038] Due to the excellent colloidal stability of the particulate component (A) due to the high molecular weight organic compound (A2) as a dispersant, dilution is carried out with deionized water (κ<1 μS cm ) in order to make the process according to the invention as resource-efficient as possible. -1 ), particularly preferably with tap water. In view of the underlying technical application, tap water contains at least 0.5 mmol / L of alkaline earth metal ions.

[0039] The presence of the thickener (B), in combination with the particulate component, imparts thixotropic flow behavior to the aqueous dispersion, thereby preventing the irreversible formation of aggregates in the particulate component of the dispersion from which the primary particles cannot be released. The addition of the thickener is preferably controlled so that the aqueous dispersion has a maximum kinematic viscosity of at least 1000 Pa·s, but preferably less than 5000 Pa·s, at a temperature of 25°C over a shear rate range of 0.001 to 0.25 per second. It also preferably exhibits shear-thinning behavior at 25°C at shear rates above the shear rate at which the maximum kinematic viscosity occurs, i.e., the viscosity decreases as the shear rate increases, resulting in the entire aqueous dispersion exhibiting thixotropic flow behavior. In this case, the viscosity over the specified shear rate range can be determined using a cone-plate viscometer with a cone diameter of 35 mm and a gap width of 0.047 mm.

[0040] The thickener of component (B) is a polymeric compound or a solution of deionized water (κ<1μScm) at a temperature of 25°C. -1 A defined mixture of chemical compounds, as a 0.5% by weight component, has a Brookfield viscosity of at least 100 mPa·s at a shear rate of 60 rpm (= revolutions per minute) using a size 2 spindle. To determine its thickening properties, the mixture must be mixed with water by adding the corresponding amount of polymeric compound to an aqueous phase at 25°C while stirring, then placing the homogenized mixture in an ultrasonic bath to remove air bubbles and leaving it for 24 hours. The viscosity reading is then taken within 5 seconds of applying a shear rate of 60 rpm with a number 2 spindle.

[0041] The aqueous dispersion according to the present invention preferably contains a total of at least 0.5% by weight, but preferably not more than 4% by weight, particularly preferably not more than 3% by weight, of one or more thickeners according to component (B), and the total content of polymeric organic compounds in the non-particulate component 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-mentioned ultrafiltration after drying to a constant mass at 105°C, i.e., the solids content after the particulate component has been separated by ultrafiltration.

[0042] Certain classes of polymeric compounds are particularly suitable thickeners according to component (B) and are readily commercially available. In this context, the thickener according to component (B) is particularly preferably selected from polymeric organic compounds, which in turn are preferably selected from polysaccharides, cellulose derivatives, aminoplasts, polyvinyl alcohols, polyvinylpyrrolidones, polyurethanes and / or urea-urethane resins, particularly preferably urea-urethane resins.

[0043] The urea urethane resin as a thickener according to component (B) of the preferred method according to the present invention for producing an aqueous colloidal solution starting from an aqueous dispersion is a mixture of polymeric compounds resulting from the reaction of a polyisocyanate with a polyol and a mono- and / or diamine. In a preferred embodiment, the urea urethane resin is obtained from a polyisocyanate preferably selected from 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 2,4-toluene diisocyanate and / or m-xylylene diisocyanate. In a particularly preferred embodiment, the urea urethane resin is obtained from a polyol selected from polyoxyalkylene diols, particularly preferably polyoxyethylene glycols, which in turn preferably consist of at least 6, particularly preferably at least 8, particularly more preferably at least 10, but preferably less than 26, particularly preferably less than 23 oxyalkylene units.

[0044] Particularly suitable and therefore preferred urea-urethane resins according to the present invention can be obtained 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 further reaction with a primary monoamine and / or a primary diamine, such as m-xylylenediamine. Urea-urethane resins containing neither free nor blocked isocyanate groups are particularly preferred. As a component of the aqueous dispersion from which the aqueous colloidal solution of the present invention can be obtained by dilution, such urea-urethane resins promote the formation of loose aggregates of primary particles, which are stabilized in the aqueous phase and protected from further aggregation to the extent that settling of the particulate components in the aqueous dispersion is largely prevented. To further enhance this property profile, urea-urethane resins containing neither free or blocked isocyanate groups nor terminal amine groups are preferably used as component (B). Thus, in a preferred embodiment, the thickener, component (B), which is a urea-urethane resin, has an amine value of less than 8 mg KOH / g, particularly preferably less than 5 mg KOH / g, and particularly preferably less than 2 mg KOH / g, as determined according to the method described above for the organic polymeric compound (A2). Since the thickener is substantially dissolved in the aqueous phase, it can be allocated to the non-particulate component of the aqueous dispersion, and component (A2) is substantially bound to the particulate component (A). The aqueous dispersion is preferably an activated colloidal aqueous solution, in which the total amine value of the polymeric organic compound in the non-particulate component is preferably less than 16 mg KOH / g, particularly preferably less than 10 mg KOH / g, and particularly preferably less than 4 mg KOH / g. It is further preferred that the urea-urethane resin have a hydroxyl value in the range of 10 to 100 mg KOH / g, particularly preferably in the range of 20 to 60 mg KOH / g, as determined according to Method A of European Pharmacopoeia 9.0 01 / 2008:20503.With regard to the molecular weight, weight-average molar masses of the urea-urethane resins in the range of 1000 to 10000 g / mol, preferably in the range of 2000 to 6000 g / mol, are advantageous according to the invention and are therefore preferably determined experimentally in each case, as described above in connection with the definition of the polymeric compound according to the invention.

[0045] Without the addition of an auxiliary agent, the pH of the dispersion to provide the aqueous colloidal solution for activation in the method according to the invention is usually in the range of 6.0 to 9.0, and therefore such a pH range is preferred according to the invention. However, for compatibility with the actual, conventional alkaline aqueous colloidal solutions in the activation step, it is advantageous to have the pH of the aqueous dispersion, as necessary, above 7.2, particularly preferably above 8.0, as a result of the addition of compounds that react in an alkaline manner. Because some polyvalent metal cations have amphoteric properties and can therefore desorb from the particulate components at higher pH values, the alkalinity of the aqueous dispersion according to the invention is ideally limited, so that the pH of the aqueous dispersion is preferably below 10, particularly preferably below 9.0.

[0046] The aqueous dispersion described above for providing the aqueous colloidal solution preferably includes, as part thereof: i) obtaining a pigment paste by triturating 10 parts by weight of the inorganic particulate compound (A1) with 0.5 to 2 parts by weight of the polymeric organic compound (A2) in the presence of 4 to 7 parts by weight of water and grinding, after dilution 1000 times with water, for example by means of a Zetasizer® Nano ZS, Malvern Panalytical GmbH, until a D50 value of less than 1 μm is reached as determined by dynamic light scattering; ii) The pigment paste is mixed with at least 5% by weight of dispersed particulate component (A) and an amount of water, preferably deionized water (κ<1 μS cm ), such that the pigment paste has a maximum kinematic viscosity of at least 1000 Pa·s at a temperature of 25°C in the shear rate range of 0.001 to 0.25 per second. -1 ) or tap water, and diluting with a thickener (B); and iii) It can be obtained by using an alkaline reactive compound and setting the pH in the range of 7.2 to 10.0; Preferred embodiments of the dispersion are similarly obtained by selecting the corresponding components (A1), (A2) and (A) in each case provided as needed or in the amounts required, as described in connection with the aqueous colloidal solutions.

[0047] The aqueous dispersion may also contain auxiliary agents selected from, for example, preservatives, wetting agents and antifoaming agents, which are contained in the amounts required for the relevant functions. The content of auxiliary agents, particularly preferably other compounds, in the non-particulate component that are not thickeners or compounds that 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 manner are water-soluble (water solubility: κ<1 μS cm -1 (at least 10 g per kg of water), with a pK above 8.0 for the first protonation step B It has a value.

[0048] The resource-saving method control according to the present invention is particularly effective in the case of continuous zinc phosphate treatment of components, i.e., during the operation of a pretreatment line for zinc phosphate treatment. Therefore, in a preferred embodiment of the method according to the present invention, a large proportion of a large number of specific components, each at least partially composed of a metal material having at least one zinc surface, is treated continuously. Continuous pretreatment is the case when, according to the present invention, a series of components are first activated and then zinc phosphated, respectively, and for this purpose, the series of components are brought into contact with activation and zinc phosphate treatment baths provided in a system tank, with each component being contacted one after the other, and therefore at different times. In this case, the system tank is a container that contains an aqueous colloidal solution for activation purposes or an acidic aqueous composition for phosphating purposes.

[0049] To reduce the carryover of alkaline components into the acidic aqueous composition for zinc phosphate treatment, a rinsing step may be performed between activation (i) and zinc phosphate treatment (ii), but to maintain complete activation of the metal surface, the rinsing step is preferably omitted. The rinsing step is used solely to completely or partially remove soluble residues, particles, and active components carried over from the treated component by adhering to the component from the previous wet chemical treatment step, without including the metallic or semimetallic active components contained in the rinsing solution itself and already consumed by contacting the metal surface of the component with the rinsing solution. For example, the rinsing solution may simply be tap water or deionized water, or, if necessary, may contain a surface-active compound to improve wetting by the rinsing solution.

[0050] For the purpose of activation of the metallic material, the layer-forming zinc phosphating treatment and the formation of a semi-crystalline coating, the phosphating treatment in process step (ii) preferably involves contacting the surface with an acidic aqueous composition containing 5 to 50 g / L of phosphate ions, 0.3 to 3 g / L of zinc ions and some 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.

[0051] For example, as required for zinc phosphate treatment of automobile bodies at least partially made of aluminum, when zinc phosphate treatment is performed on components containing not only zinc surfaces but also iron or aluminum surfaces, a source of free fluoride or free fluoride ions is essential for the layer-forming zinc phosphate treatment process. In this regard, it is advantageous if the amount of free fluoride in the acidic aqueous composition is at least 0.5 mmol / kg, particularly preferably at least 2 mmol / kg. The concentration of free fluoride should not exceed a value at which the phosphate coating has a predominantly easily wipeable adhesive property, because this adhesion cannot be avoided even by a disproportionate increase in the amount of particulate components in the aqueous colloidal solution of activation. Therefore, in the method of the present invention based on activation (i) followed by zinc phosphate treatment (ii), it is also economically advantageous and preferred that the concentration of free fluoride in the acidic aqueous composition of zinc phosphate treatment is less than 15 mmol / kg, particularly preferably less than 10 mmol / kg, and particularly preferably less than 8 mmol / kg.

[0052] The amount of free fluoride can be determined potentiometrically by a fluoride-sensitive measuring electrode in the relevant acidic aqueous composition at 20°C after calibration with a fluoride-containing buffer without pH buffering. Suitable sources of free fluoride ions are hydrofluoric acid and its water-soluble salts, such as ammonium bifluoride and sodium fluoride, and complex fluorides of the elements Zr, Ti and / or Si, in particular complex fluorides of the element Si. 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. The salts of hydrofluoric acid are preferably dissolved in deionized water at 60°C (κ<1 μS cm), calculated as F. -1 ) is at least 1 g / L is water-soluble within the meaning of the present invention.

[0053] In such a process according to the invention in which zinc phosphate treatment is carried out in step (ii) in order to suppress what is known as "pin-holing" on the surface of metal materials made of zinc, it is preferred that the source of free fluoride is at least partly selected from complex fluorides of the element Si, in particular hexafluorosilicic acid and its salts. The term pin-holing is understood by those skilled in the art of phosphating to mean the phenomenon of localized deposition of amorphous white zinc phosphate in an otherwise crystalline phosphate layer on the treated zinc surface or on the treated galvanized or alloy-galvanized steel surface.

[0054] In step (ii) of the method according to the invention, the preferred pH of the acidic aqueous composition is above 2.5, particularly preferably above 2.7, but preferably below 3.5, particularly preferably below 3.3. The amount of free acid in the acidic aqueous composition of the zinc phosphate treatment in step (ii) of the method is preferably at least 0.4 points, but preferably not more than 3.0, particularly preferably not more than 2.0. The percentage of free acid in points is determined by diluting a 10 ml sample volume of the acidic aqueous composition to 50 ml and titrating it to pH 3.6 with 0.1 N sodium hydroxide solution. The amount of sodium hydroxide solution consumed in ml indicates the number of points of free acid.

[0055] Typical additions of additives for zinc phosphate treatments can be made in the context of the present invention as well, so that the acidic aqueous composition of process step (ii) can further contain conventional accelerators such as hydrogen peroxide, nitrites, hydroxylamines, nitroguanidine and / or N-methylmorpholine-N-oxide, as well as cations of the metals manganese, calcium and / or iron in the form of water-soluble salts which have a positive effect on layer formation.Embodiments in which less than 10 ppm in total of nickel and / or cobalt ions are present in the acidic aqueous composition for zinc phosphate treatment in process step (ii) are particularly preferred from an environmental point of view.

[0056] In the process according to the invention, a good coating primer for subsequent dip coating is produced in the course of applying a substantially organic cover layer. Thus, in a preferred embodiment of the process according to the invention, the zinc phosphate treatment, with or without intermediate rinsing and / or drying steps, or preferably with a rinsing step but without a drying step, is followed by dip coating, particularly preferably electrocoating, especially more preferably cathodic electrocoating, which preferably contains a water-soluble or water-dispersible salt of yttrium and / or bismuth in addition to a dispersing resin, preferably comprising an amine-modified polyepoxide. The initial disclosure of this specification encompasses at least the following aspects. [1] A method for the anticorrosive pretreatment of a metallic material having at least part of the surface thereof zinc or a component at least partly composed of such a metallic material, said metallic material or said component being subjected in successive method steps first to an activation (i) and then to a zinc phosphate treatment (ii), said activation in method step (i) being carried out by contacting said metallic material or said component with an aqueous colloidal solution, said aqueous colloidal solution containing in its dispersed particulate component (a): (a1) at least one particulate inorganic compound composed of a phosphate salt of a polyvalent metal cation selected at least in part from hopeite, phosphophyllite, scholzite, and / or hallolite; and (a2) at least one polymeric organic compound composed at least in part of styrene and / or an α-olefin having 5 or fewer carbon atoms, further comprising units of maleic acid, its anhydride and / or its imide, and further comprising polyoxyalkylene units; Including, The content of particulate components in the aqueous colloidal solution is at least 4 g / kg based on the aqueous colloidal solution; and In process step (ii), 2.0 g / m 2 A zinc phosphate layer having a layer weight of less than 1000 .mu.m is deposited on the surface of the zinc. [2] The method according to [1], characterized in that in the aqueous colloidal solution, the content of condensed phosphate dissolved in water is less than 0.25, preferably less than 0.20, particularly preferably less than 0.15, more particularly preferably less than 0.10, based in each case on the phosphate content of the at least one particulate compound, which is based on the element P. [3] The method according to [1] or [2], characterized in that the aqueous colloidal solution in activation (i) has an alkaline pH, preferably above 8.0, particularly preferably above 9.0, but preferably below 11.0. [4] PO contained in the at least one particulate inorganic compound (a1). 4 The method according to any one of the above items [1] to [3], characterized in that the phosphate content, calculated as ρ = ρ ... [5] The method according to any one of the above [1] to [4], characterized in that the polymeric organic compound (a2) in the aqueous colloidal solution contains polyoxyalkylene units in its side chains, and the content of polyoxyalkylene units in the entire polymeric organic compound (a2) is preferably at least 40% by weight, particularly preferably at least 50% by weight, and particularly preferably not more than 70% by weight. [6] The method according to any one of the above items [1] to [5], characterized in that the organic polymer compound (a2) of the aqueous colloidal solution also contains imidazole units, preferably in such a way that the polyoxyalkylene units of the organic polymer compound (a2) are at least partially end-capped with imidazole groups. [7] The method according to any one of the above items [1] to [6], characterized in that the aqueous colloidal solution contains as a further component b) at least one thickener, preferably selected from urea-urethane resins, preferably urea-urethane resins having an amine value of less than 8 mg KOH / g, particularly preferably less than 5 mg KOH / g, and very preferably less than 2 mg KOH / g. [8] The method according to any one of [1] to [7], wherein the total amount of the polymeric organic compound based on the particulate component of the aqueous colloidal solution is at least 3% by weight, preferably at least 6% by weight, but preferably not more than 15% by weight. [9] The method according to any one of [1] to [8] above, wherein the aqueous colloidal solution has a D50 value of less than 1 μm, preferably less than 0.4 μm.

[10] The method according to any one of the above [1] to [9], characterized in that the content of the particulate components in the aqueous colloidal solution is in each case at least 6 g / kg, preferably at least 8 g / kg, particularly preferably at least 10 g / kg, but preferably not more than 20 g / kg, particularly preferably not more than 15 g / kg, based on the aqueous colloidal solution.

[11] The colloidal aqueous solution is obtained as an aqueous dispersion diluted 20 to 100,000 times, - at least 5% by weight, based on said aqueous dispersion, of dispersed particulate component (A), (A1) at least one particulate inorganic compound composed of a phosphate salt of a polyvalent metal cation selected at least in part from hopeite, phosphophyllite, scholzite and / or hallolite; (A2) At least one polymeric organic compound composed at least in part of styrene and / or an α-olefin having 5 or fewer carbon atoms, further comprising units of maleic acid, its anhydride and / or its imide, and further comprising polyoxyalkylene units. a dispersed particulate component (A) comprising, in order, optionally at least one thickener, preferably chosen from urea-urethane resins, particularly preferably urea-urethane resins having an amine number of less than 8 mg KOH / g, preferably less than 5 mg KOH / g, particularly preferably less than 2 mg KOH / g The method according to any one of the above [1] to

[10] , comprising:

[12] In process step (ii), 1.8 g / m 2 less than 1.6 g / m 2 less than 1.5 g / m2 The method according to any one of the above [1] to

[11] , wherein a zinc phosphate layer having a layer weight of less than 10 ...

[13] The zinc phosphate treatment in process step (ii) is 4 The method according to any one of the above items [1] to

[12] , characterized in that the method is carried out by contacting the fluoride-containing material with an acidic aqueous composition containing 5 to 50 g / kg of phosphate, 0.3 to 3 g / kg of zinc ions, and an amount of free fluoride that may contain less than 0.1 g / kg of nickel and cobalt ions in total, all dissolved in water, calculated as follows:

[14] A component having, in addition to a zinc surface, also an iron and / or aluminum surface is treated, and in process step (ii) 2.0 g / m 2 less than 1.8 g / m 2 less than 1.6 g / m 2 less than, very particularly preferably 1.5 g / m 2 The method according to any one of the above [1] to

[13] , characterized in that a zinc phosphate layer having a layer weight of is preferably deposited on all surfaces of zinc, iron and aluminum.

Claims

1. 1. A method for the anticorrosion pretreatment of a metal material having a zinc, iron or aluminum surface or a component at least partly composed of said metal material, said metal material or said component being subjected in successive method steps first to an activation (i) and then to a zinc phosphate treatment (ii), said activation in method step (i) being carried out by contacting said metal material or said component with an aqueous colloidal solution, said aqueous colloidal solution comprising in its dispersed particulate component (a): (a1) at least one particulate inorganic compound composed of a phosphate of a polyvalent metal cation selected at least in part from hopeite, phosphophyllite, scholzite, and / or hallolite; and (a2) At least one polymeric organic compound which is at least partially composed of styrene and / or an α-olefin having 5 or less carbon atoms and further contains units of maleic acid, its anhydride and / or its imide, and polyoxyalkylene units, the polyoxyalkylene units being contained in an amount of at least 40% by weight based on the total weight of the polymeric organic compound. Including, The content of dispersed particulate component (a) in the aqueous colloidal solution is 4 g / kg to 20 g / kg based on the aqueous colloidal solution; and In process step (ii), 2.0 g / m ２ A zinc phosphate layer having a layer weight of less than 1000 .mu.m is deposited on the surface of the zinc.

2. 2. The method according to claim 1, wherein the content of condensed phosphate dissolved in water in the aqueous colloidal solution is less than 0.25 based on the element P, based on the phosphate content of the at least one particulate inorganic compound.

3. 3. The method according to claim 1 or 2, characterized in that the aqueous colloidal solution in activation (i) has an alkaline pH.

4. A method according to any one of claims 1 to 3, characterized in that the content of phosphate contained in the at least one particulate inorganic compound (a1), calculated as PO4, is at least 25% by weight based on the dispersed particulate components of the aqueous colloidal solution.

5. 5. The method according to claim 1, wherein the polymeric organic compound (a2) in the aqueous colloidal solution contains polyoxyalkylene units in its side chains, and the content of polyoxyalkylene units in the entire polymeric organic compound (a2) is at least 40% by weight but not more than 70% by weight.

6. The method according to any one of claims 1 to 5, wherein the organic polymer compound (a2) in the aqueous colloidal solution has an imidazole unit.

7. 7. The method according to claim 1, wherein the aqueous colloidal solution contains as further component b) at least one thickener selected from urea-urethane resins.

8. 8. The method of claim 1, wherein the dispersed particulate component of the aqueous colloidal solution has a total polymeric organic compound content of at least 3% by weight but not more than 15% by weight based on the dispersed particulate component.

9. 9. The method according to claim 1, wherein the dispersed particulate components contained in the aqueous colloidal solution have a D50 value of less than 1 μm.

10. 10. The method according to any one of claims 1 to 9, characterized in that the content of the dispersed particulate components in the aqueous colloidal solution is at least 6 g / kg but not more than 15 g / kg, based on the aqueous colloidal solution.

11. In process step (ii), 1.8 g / m ２ 11. The method according to claim 1, wherein a zinc phosphate layer having a layer weight of less than 1000 ppm is deposited on the surface of zinc, iron or aluminum.

12. 12. The method according to any one of claims 1 to 11, characterized in that the zinc phosphate treatment in method step (ii) is carried out by contact with an acidic aqueous composition containing 5 to 50 g / kg of phosphate (calculated as PO 4 and based on the total amount of the acidic aqueous composition) dissolved in water, 0.3 to 3 g / kg of zinc ions, and free fluoride in an amount that may contain ions of the elements nickel and cobalt in total of less than 0.1 g / kg.

13. A component having, in addition to a zinc surface, also an iron and / or aluminum surface is treated, and in process step (ii) 2.0 g / m ２ 13. The method according to claim 1, wherein a zinc phosphate layer having a layer weight of less than 1000 .mu.m is deposited on all surfaces of zinc, iron and aluminum.