Multi-step process for activated zinc phosphate treatment of metal components

Abstract

The present invention relates to a process for the anti-corrosion pretreatment of a series of multiple components, each of which has at least a partial zinc and / or iron surface, at least a portion of which is initially activated in a targeted manner for subsequent zinc phosphate treatment. Targeted activation is achieved by controlled distribution of an aqueous dispersion to wet the zinc and / or iron surfaces, thus ensuring resource-saving activation. The aqueous dispersion for activation wetting contains particulate components dispersed in water, at least in part composed of hopeite, phosphophyllite, scholzite, and / or hallolite, provided as a dispersion of these crystalline solids stabilized by at least one polymeric organic compound. Again, the phosphate treatment quality of the acidic aqueous composition for zinc phosphate treatment is ensured and maintained by adding a certain amount of aqueous dispersion, particularly the same aqueous dispersion also used for activation wetting.

Description

[Technical Field]

[0001] The present invention relates to a process for the anti-corrosion pretreatment of a series of multiple components, each of which has a surface made at least in part of zinc and / or iron, at least some of which are initially targeted and activated for subsequent zinc phosphate treatment. Targeted activation is achieved by controlled dispensing of an aqueous dispersion for wetting the aforementioned zinc and / or iron surfaces ("activation wetting") to ensure resource-efficient activation. The aqueous dispersion for activation wetting contains particulate components dispersed in water, at least in part composed of hopeite, phosphophyllite, scholzite, and / or hallolite, provided as a dispersion of these crystalline solids stabilized by at least one polymeric organic compound. The phosphate treatment quality of the acidic aqueous composition for zinc phosphate treatment is then ensured and maintained by adding a certain amount of aqueous dispersion, particularly the same aqueous dispersion also used for activation wetting. [Background technology]

[0002] Layer-forming phosphating is a process for applying crystalline corrosion-resistant coatings to metal surfaces, particularly those of iron, zinc, and aluminum, that has been used and extensively studied for decades. The zinc phosphating process, established specifically for corrosion protection, is carried out in layers several micrometers thick and is based on the corrosive pickling of metal materials in an acidic aqueous solution containing zinc ions and phosphate, during which poorly soluble crystallites form near the surface and precipitate directly at the interface with the metal material, where they continue to grow.

[0003] Zinc phosphate treatment is usually designed to produce a homogeneous, closed, dense crystalline coating on the surface of iron, zinc, and aluminum metals. Otherwise, good corrosion protection and a good coating base cannot be achieved. A homogeneous, closed coating is usually obtained at a concentration of 2 g / m. 2is reliably achieved during zinc phosphate treatment in excess of a layer weight of 10 ...

[0004] To achieve such a homogeneous, closed coating with a high degree of compactness or density of phosphate crystallites, in the prior art, zinc phosphate treatment typically begins by activating the metal surface of the component to be phosphated. Activation is a wet-chemical process step, conventionally carried out by contacting the surface with an aqueous colloidal solution of phosphate (the "activation step"), which, as long as they remain immobilized on the metal surface, act as growth nuclei for the formation of a crystalline coating in the subsequent phosphating process, thereby increasing the number density of growing crystallites and thus producing a dense, crystalline zinc phosphate layer with excellent corrosion protection and, due to its high charge transfer resistance, also excellent electrodeposition properties.

[0005] Depending on the metal surface to be phosphated, it is necessary to adjust the pickling process in the zinc phosphating stage not only by adjusting the performance of the activation stage mentioned above, but also by adjusting the concentration of the active components, which often requires intensive activation in the immersion process, and at the same time, sufficient pickling in the presence of fluoride ions in the phosphating stage in order to achieve correspondingly high layer weights on all surfaces of the zinc, iron or steel and aluminum components, especially in the case of metal components such as car bodies made of a mixture of different materials.

[0006] However, very recently, a process has been described in WO 2022 / 048963 that even makes it possible to dispense with the conventional activation of the surface before zinc phosphating, provided that the zinc phosphating bath itself has an activating effect and therefore contains a sufficient amount of phosphate in dispersed form.

[0007] This process for zinc phosphating with integrated activation can be used to reliably phosphate different metals to form layers, but the proportion of dispersed phosphate with activating effect in the acidic aqueous composition of the phosphating bath must always be adapted to the component being treated. When components made of different metals are treated to protect them against corrosion, the metal surface that is most difficult to activate always determines the total consumption of active ingredient, i.e., dispersed phosphate. Accepting suboptimal activation in order to reduce the consumption of dispersed phosphate in the activation or phosphating stage inevitably leads to a higher phosphate layer weight, especially on zinc or iron surfaces, and therefore at the expense of a higher consumption of active ingredient during the phosphating stage. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2022 / 048963 Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, it is necessary to fully utilize the undoubted existing process economic advantages of the integrated process of WO 2022 / 048963, which consists of a reduced pretreatment sequence that can be controlled with less effort and in which the consumption of active ingredients can be reduced as much as possible, without sacrificing the phosphating quality, which is equivalent to a homogeneous, closed, and as finely crystalline phosphate layer as possible with a low layer weight on the zinc and / or iron surface of the treated component, very specifically on the zinc surface. Such a resource-saving process for activating zinc phosphating must be suitable for sufficiently activating components made of different metal materials to form layers with high phosphating quality, despite the specific requirements of the different materials.

[0010] In this case, the operational profile was resolved by selective and controlled dispensing of aqueous dispersions for activating wetting of metal surfaces prior to the actual integrated zinc phosphating process. The activating wetting of zinc and / or iron surfaces surprisingly allows a significant reduction in the zinc phosphating layer weight with the same phosphating quality, thus also significantly reducing the consumption of active ingredients during the zinc phosphating process. DETAILED DESCRIPTION OF THE INVENTION

[0011] The invention relates in particular to a process for the anti-corrosion pretreatment of a series of components, each component of the series having at least partly a zinc and / or iron surface, which is first subjected to a process step (i) for activating the zinc and / or iron surface, followed immediately by a process step (ii) for zinc phosphating,

[0012] In process step (i), at least the zinc and / or iron surface of each of the series of components is contacted with an aqueous dispersion containing a water-dispersed particulate component (P), at least one particulate inorganic compound (P1) composed of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and / or hallolite, and at least one polymeric organic compound (P2), are contacted, said contacting being effected by dispensing an aqueous dispersion from a source such that no more than 1.00 liters of aqueous dispersion is dispensed per square meter of surface of each component in the series, preferably per square meter of zinc and / or iron surface of each component in the series, into contact with the dispersion; In process step (ii), at least the zinc and / or iron surface of each component in the series is contacted with an acidic aqueous composition having free acid at a point greater than 0; (A) 5 to 50 g / kg of phosphate dissolved in water, calculated as PO4; (B) 0.3 to 3 g / kg zinc ions; (C) free fluoride, and (D) a water-dispersed particulate component comprising a phosphate salt of a polyvalent metal cation, wherein the phosphate salt is at least partially selected from hopeite, phosphophyllite, scholzite, and / or hallolite; The acidic aqueous composition can be obtained by adding a certain amount of an aqueous dispersion to an acidic aqueous composition containing components (A) to (C), and the aqueous dispersion contains a water-dispersed particle component (P), which is at least one particulate inorganic compound (P1) composed of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and / or hallolite, and at least one polymeric organic compound (P2).

[0013] A sequential pretreatment occurs when a series of individual components undergo process steps (i) and (ii) of the zinc phosphate treatment one after the other, and thus at separate times, according to the process of the invention, and thus, as intended, come into direct succession in contact with the corresponding aqueous compositions stored in a system tank. The system tank for process step (i) is a vessel in which an aqueous dispersion is held for the purpose of activating the zinc and / or iron surfaces by wetting, and the system tank for process step (ii) is correspondingly a vessel containing the acidic aqueous composition for the zinc phosphate treatment. The components can be contacted with the acidic aqueous composition in process step (ii) either in the system tank, for example by immersion, or outside the system tank, for example by spraying the acidic aqueous composition stored in the system tank onto a bath. The zinc and / or iron surfaces of each component in the series are contacted with the aqueous dispersion in process step (i), for example by wetting the surfaces to be activated outside of the system tank from which the stored aqueous dispersion is dispensed for each component, preferably by dispensing a predetermined volume of the dispersion from a source onto the surfaces to be activated such that the volume of aqueous dispersion once dispensed for each component is not returned to the system tank holding the dispersion.

[0014] The components treated according to the invention can be three-dimensional structures of any shape and design resulting from the 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 interconnected by adhesive bonding, welding and / or flange joining to form the composite structure.

[0015] The process according to the present invention is particularly effective for producing dense, closed-crystal phosphate coatings on zinc surfaces, such that a series of preferred components have at least a zinc surface. The process according to the present invention is also well suited for the layer-forming phosphate treatment of aluminum, so that even components with a mixed structure composed of zinc, iron, and aluminum materials, such as automobile bodies, can be effectively and resource-savingly phosphated according to the present invention. However, aluminum surfaces generally do not require preactivation in process step (i), and sufficient layer formation occurs when the aluminum surface is contacted with the acidic aqueous composition in process step (ii). In a specific embodiment of the process according to the present invention, the series of components having at least a zinc and / or iron surface also have a metallic aluminum surface, and the metallic aluminum surface is preferably not contacted with the aqueous dispersion dispensed in process step (i) but is contacted with the acidic aqueous composition in process step (ii).

[0016] In the context of the process according to the invention, a component has at least one surface made of zinc and / or iron if more than 50 at.% of the metallic structure on this surface is composed of zinc and / or iron to a penetration depth of at least 1 micrometer. This often applies to components made of the corresponding metallic materials, as long as the metallic material is composed of zinc and / or iron as a homogeneous material for more than 50 at.%. However, components containing zinc surfaces can also be ferrous materials provided with a metallic coating, such as electrolytic galvanized steel or hot-dip galvanized steel, which may be alloyed with iron (ZF), aluminum (ZA), and / or magnesium (ZM).

[0017] For resource-saving operation of the corrosion protection process pretreatment based on zinc phosphating in step (ii), the present invention provides that process step (ii) immediately follows the activation in step (i). In this way, on the one hand, the degree of activation of the zinc and / or iron surfaces of the component for the zinc phosphating step is maintained to the maximum, and on the other hand, the zinc phosphating step is essentially reactivated, since the particulate phosphate is introduced into the phosphating step via a wet film that adheres to the component, thus having an activating effect.

[0018] Thus, within the context of the present invention, the direct sequence of activation and zinc phosphate treatment provided in accordance with the present invention means that the component undergoes process step (i) without any intermediate rinsing or other treatment steps (especially involving further contact between the zinc or iron surface of the component and an aqueous dispersion containing the water-dispersed particulate component (P) in the manner of process step (i), or preferably between the zinc or iron surface of the component and an aqueous dispersion for activation for zinc phosphate treatment, or particularly preferably contact with an aqueous composition), and in either case, preferably no drying step is performed after process step (i) or before process step (ii). A rinsing step in this context can include one or more immediately subsequent process steps, such as rinsing with municipal water, which serve to remove as completely as possible soluble residues, particles, and / or active ingredients that inevitably remain on the surface of the component after discharge from the previous wet-chemical process step. A drying step in this context is a process of drying the component by controllable technical means, for example, by providing heat or by directional air supply.

[0019] A further advantage of the dense, closed crystalline coatings accessible on all these metal surfaces using the process according to the invention is their excellent electrocoatability, which allows for high wraparound behavior. In this respect, it is preferred that step (ii) is followed by electrocoating, particularly preferably cathodic electrocoating. In principle, this process can be used with any type of coating, especially powder coating, with an organic topcoat system as is customary in the prior art, since it provides an excellent primer.

[0020] Process step (i) - Preactivation: The aqueous dispersion is contacted to activate at least the zinc and / or iron surfaces by dispensing it from a source. Dispensing the aqueous dispersion from a source for contacting, within the meaning of the present invention, requires the use of a device for withdrawing a volume of liquid from the source, e.g., a container holding a sufficient amount of aqueous dispersion for multiple components, and a device for dispensing the withdrawn volume of liquid onto the surfaces of one or more components to be contacted. As a result, the components are not contacted in a stored aqueous dispersion, i.e., not by immersion in the stored aqueous dispersion, but by direct application, e.g., using a roller, or by spraying / misting with a partial volume of the stored aqueous dispersion withdrawn from the source. Furthermore, according to the present invention, the volume of the aqueous dispersion dispensed from the source for contacting is limited, and should be less than 1.00 liters per square meter of the surface of the component, or preferably only the zinc and / or iron surfaces of the component. This ensures that a liquid volume of the aqueous dispersion is not dispensed that is significantly greater than that required to completely wet the zinc and / or iron surfaces with a liquid film of the aqueous dispersion. It is therefore advantageous in principle if the aqueous dispersion is applied as effectively as possible to the surfaces to be treated, without excess. In a preferred embodiment of the process according to the invention, contact with the zinc and / or iron surfaces is carried out by dispensing the aqueous dispersion from a source in such a way that not more than 0.50 liters, preferably not more than 0.20 liters, of aqueous dispersion are dispensed per square meter of the surface of the component, preferably only the zinc and / or iron surfaces of the component to be activated and therefore contacted.

[0021] In this context, the surface area of ​​the aqueous dispersion dispensed onto the surface of a series of components is the surface of a polyhedron having 12 surfaces, preferably 6 surfaces, and particularly preferably a rectangular prism that completely encompasses the component in each case and thus has the smallest surface area, with each surface of the polyhedron contacting the component at least one point. If the component is an automobile body, the surface area relevant to the surface area-related dispensing of the aqueous dispersion for conditioning purposes is preferably the surface area of ​​a rectangular prism having the smallest surface area that completely surrounds the automobile body, with each surface of the rectangular prism contacting the automobile body at least one point. In a preferred embodiment of the process according to the invention, the upper limit of the surface area-related aqueous dispersion volume dispensed onto the zinc and / or iron surface is standardized. The geometric area of ​​the surface of the component made of zinc and / or iron to be activated must then be taken into account. Thus, while the treatment of flat products such as strip steel requires that the entire outer surface of the flat product is already preactivated in process step (i), the sequential treatment of car bodies in a preferred embodiment only needs to include the outer surfaces of the body made from strip steel after forming and joining, since in many cases only these are optimally phosphated to form a layer and can therefore be preactivated accordingly.

[0022] The distribution of the aqueous dispersion for contact with, and thus activation of, the zinc and / or iron surfaces requires and requires that the amount distributed from the source also at least partially reaches these surfaces. Therefore, in a preferred embodiment, the distribution of the aqueous dispersion for contact in process step (i) for sufficient activation is carried out to ensure that at least the zinc and / or iron surfaces are covered with a liquid film containing the aqueous dispersion, resulting in a volume-related coating on the zinc and / or iron surfaces of preferably no more than 1.00 liters per square meter, particularly preferably no more than 0.50 liters, very particularly preferably no more than 0.20 liters, and particularly preferably no more than 0.10 liters per square meter. In contrast to the volume of the aqueous dispersion distributed for contact, the volume coating here does not refer to the surface of the components approximated by a polyhedron, but rather to the actual geometric surface of the zinc and / or iron surfaces of a series of components, whereby the volume coating refers to the density of the liquid adhering to the surface of 1 g / cm. 3 can be determined by the weight difference after blowing off the liquid film, assuming that

[0023] It should be noted that the components are often already wetted with a liquid film, formed, for example, by rinsing with water from a rinsing step immediately preceding activation, and when transferred to the activation stage according to process step (i), prior to contact with the zinc and / or iron surfaces, this is then carried out according to the invention by absorption of the liquid volume of the aqueous dispersion in the wet film already attached to these surfaces. Such a process variant can be particularly advantageous, since the active ingredient absorbed by the wet film attached to the component is better absorbed by the pre-wetted surface of the component and then distributed more homogeneously thereon, thereby facilitating uniform activation of the subsequent zinc phosphate treatment step.

[0024] If the device for dispensing and for producing contact is sufficient to achieve as complete a wetting as possible of the zinc and / or iron surface to be activated, it may again be advantageous for reasons of efficiency to remove, for example by blowing or wiping, a wet film adhering to the component from a previous treatment step immediately before process step (i) or immediately before the zone where the aqueous dispersion is dispensed for contact with the surface, in order to use as efficiently as possible only that aqueous dispersion which has a relatively low particle content but is still sufficient to bring about the desired activation.

[0025] The formation of a liquid film containing the aqueous dispersion on the zinc and / or iron surface in process step (i) can be confirmed by adding a fluorescent marker to the aqueous dispersion source. Detection can then be performed by irradiating with UV light and recording the corresponding fluorescence with a suitable camera, thereby enabling imaging control of the wetting of the component surface with the aqueous dispersion. This is particularly useful when components with complex surface topography must be pretreated and the type of aqueous dispersion distribution, such as the relative orientation and spacing of the spray lance to the component, must first be adjusted in an iterative process so that the zinc and / or iron surface comes into contact with the aqueous dispersion, and in particular so that these surfaces are covered with a liquid film containing the aqueous dispersion. The latter preferred condition does not have to be met directly by contacting the aqueous dispersion from the source with the surface, i.e. directly by the application device, but it is sufficient if a liquid film containing the aqueous dispersion in contact with the zinc and / or iron surface is formed before process step (ii), i.e. before the component is introduced into the zinc phosphate treatment process, preferably at least 5 seconds, particularly preferably at least 10 seconds, very particularly preferably at least 20 seconds before contact with the acidic aqueous composition in process step (ii).

[0026] For controlled distribution of the aqueous dispersion required in the process according to the invention for activating wetting of zinc and / or iron surfaces, it is advantageous and therefore even more preferred that in process step (i) the aqueous dispersion is distributed as a spray, spray mist, or liquid film, particularly preferably as a spray and / or spray mist, and particularly preferably as a spray mist. The aqueous dispersion is brought into contact with the surface of the component to be activated as a spray and / or spray mist by a spraying and misting process established in the prior art, which can be carried out in a locally limited manner by a spray lance and / or in a manner that at least partially encompasses the component by a spray ring that can be equipped with multiple atomizer nozzles. The spraying device used for distributing the spray and / or spray mist is, for example, a pressure atomizer, a rotary atomizer, or a two-substance atomizer. Depending on the complexity and geometry of the set of components, the liquid film can be applied to the component by direct application with a roller, cloth, brush, paintbrush, or similar tool for applying liquids.

[0027] A preferred controlled and efficient activated wetting with the aqueous dispersion is achieved by setting up a spray that targets the zinc and / or iron surfaces to be wetted and / or by providing a spray mist through which the components are transported together with the conveyor frame and on a transport path such that the surfaces of the components to be wetted are exposed to a closed liquid film, preferably containing the aqueous dispersion, at a given volumetric flow rate, before the components come into contact with the acidic aqueous composition for zinc phosphate treatment in the immediately following process step (ii).

[0028] For example, to form a liquid film covering the surface of the component and thus distribute the amount of aqueous dispersion necessary for effective activated wetting, the dispersion dispersed as a spray and / or spray mist in process step (i) according to the present invention preferably has an average droplet size of less than 100 μm, particularly preferably less than 60 μm, and particularly preferably less than 40 μm. At an average droplet size of less than 40 μm, the aqueous dispersion is atomized so strongly that it crosses the boundary with the aerosol, forming a spray mist. Further atomization of the aqueous dispersion reduces the average droplet size, and the droplets are gradually held in suspension and no longer subject to gravity. The suspended spray mist then also moves and, possibly, rotates due to the air mass displaced during transport of the component through the spray chamber, further hindering directional impact on the surface of the zinc and / or iron to be activated and making it more difficult for the component surface to be uniformly wetted by the liquid film. Therefore, it is preferred that the dispensed aqueous dispersion in process step (i) has an average droplet size of 5 μm or more, particularly preferably 10 μm or more.

[0029] It is also advantageous to form a closed liquid film containing the aqueous dispersion on the surface of the contacted component when the spray and / or spray mist of the aqueous dispersion is distributed so that the droplets have an average droplet size of less than 5 m / s, preferably less than 2 m / s, and particularly preferably less than 1 m / s. This applies in particular to sprays and / or spray mist with an average droplet size of less than 100 μm, particularly preferably less than 60 μm, and particularly preferably less than 40 μm.

[0030] In accordance with the present invention, the mean droplet size and mean velocity of the droplets of the spray or spray mist are determined at the location of the geometric centroid of the polyhedron surrounding the component, which is also used to determine the amount of drug dispensed per surface area of ​​the component, as described above, which can be determined by light scattering and phase Doppler anemometry.

[0031] The preferred embodiments described herein regarding how the aqueous dispersion can be distributed to contact at least the zinc and / or iron surfaces provide a highly efficient process in which the amount of aqueous dispersion distributed from the source is essentially applied only to the zinc and / or iron surfaces of the component being activated. At the same time, the proportion of aqueous dispersion introduced by the component into the zinc phosphate treatment stage serves to at least partially compensate for the proportion of particles of the acidic aqueous zinc phosphate treatment composition consumed during the activated zinc phosphate treatment process and removed from the zinc phosphate treatment stage. For the same purpose, the proportion of aqueous dispersion components distributed but not remaining on the component in process step (i) can also be transferred to the zinc phosphate treatment stage to maintain activation performance. Therefore, according to the invention, a process is preferred in which the proportion of the aqueous dispersion that is dispensed in process step (i) and brought into contact with at least the zinc and / or iron surfaces of the component, but that sinks to the bottom as overspray or runs off the component and remains in the spray chamber of process step (i) and does not remain as a wet film on the component until it is contacted with the acidic aqueous composition for zinc phosphate treatment in process step (ii), is at least partially mixed and added to the acidic aqueous composition in process step (ii), and in either case is preferably not returned either partially or completely to the source.

[0032] For sufficient preactivation of at least the zinc and / or iron surfaces of the series of components, the aqueous dispersion used must contain a water-dispersed particulate component (P) consisting of a phosphate salt of a polyvalent metal cation (P1) and a polymeric organic compound (P2) that contributes to the stabilization of the dispersion.

[0033] At this point, it should be emphasized that the preferred proportion of phosphate (P1), calculated as PO4, contained in the at least one particulate inorganic compound is at least 25% by weight, particularly preferably at least 35% by weight, particularly preferably at least 40% by weight, and very particularly preferably at least 45% by weight, based on the dispersed inorganic particle component (P1) of the aqueous dispersion. Further preferred embodiments of the inorganic particle component (P1) can be derived from the corresponding preferred embodiments of the inorganic particle component (P1) of the aqueous dispersion in process step (ii), as already explained.

[0034] For excellent dispersion stability, the polymeric organic compound (P2) in the particulate component (P) of the aqueous dispersion is at least partially composed of styrene and / or α-olefins having not more than 5 carbon atoms. The polymeric organic compound (P2) further comprises maleic acid, its anhydride, and / or its imide units in its side chains, preferably further comprising polyoxyalkylene units, particularly preferably polyoxyalkylene units, the side chains of which are at least partially end-capped with aliphatic alkyl groups having not more than 4 carbon atoms. Furthermore, it is particularly advantageous if the polymeric organic compound (P2) in the particulate component (P) of the aqueous dispersion further comprises imidazole units. The proportion of polyoxyalkylene units in the overall polymeric organic compound (P2) is preferably at least 40% by weight, particularly preferably at least 50% by weight, but preferably not more than 70% by weight. Further preferred embodiments of the polymeric organic compound (P2) can be derived from the corresponding preferred embodiments of the polymeric organic compound (P2) of the aqueous dispersion in process step (ii), as already explained.

[0035] In addition to the above-mentioned embodiments of the particle component (P) of the aqueous dispersion in process step (i), the presence of a thickener is advantageous for providing a stable dispersion that can be stored in the system tank of process step (i) for a relatively long period of time.Therefore, in a preferred embodiment of the process according to the invention, the aqueous dispersion of process step (i) contains at least one thickener as an additional component, preferably selected from urea-urethane resins, particularly preferably urea-urethane resins with 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; further preferred embodiments of the thickener are described in relation to the aqueous dispersion added in process step (ii) of zinc phosphate treatment, which are also advantageous and are included here as preferred embodiments for the aqueous dispersion used for preactivation.

[0036] Further preferred embodiments of the aqueous dispersion containing the water-dispersed particle component (P) used in step (i) according to the present invention can be found in the description of particularly suitable activating coagents.

[0037] The degree to which the zinc and / or iron surfaces are preactivated can be controlled by the particle proportion of the aqueous dispersion dispersed in water. It has been found that the zinc and / or iron surfaces are particularly reliably preactivated during typical activation times, i.e., contact periods ranging from 5 to 120 seconds, when the particle proportion (P) is at least 0.060 g / kg of the aqueous dispersion. A shorter activation time can be compensated for by a higher particle proportion (P), such that it is advantageous when the water-dispersed particle component (P) of the aqueous dispersion in process step (i) as a whole is at least 0.060 g / kg, particularly preferably at least 0.100 g / kg. A significantly higher content is associated with a higher economic expenditure, which is not worthwhile for the significant improvement in the subsequent compactness of the zinc phosphate coating, nor is it often necessary to reactivate the particle proportion in the acidic aqueous composition for zinc phosphate treatment due to carryover, thus hindering the present invention's aim of establishing a particularly resource-efficient zinc phosphate treatment process. Therefore, the water-dispersed particle component (P) of the aqueous dispersion in process step (i) preferably does not exceed 5.0 g / kg, particularly preferably does not exceed 1.0 g / kg of the aqueous dispersion.

[0038] The pH value of the aqueous dispersion for preactivation is preferably set so as to avoid pickling of the metal material of the component, in particular of components made of zinc, iron or aluminum. The aqueous dispersion in process step (i) for activating the zinc surface therefore has a pH value of more than 6.0, particularly preferably more than 6.5, but preferably not more than 9.0, particularly preferably not more than 8.5, very particularly preferably not more than 8.0, particularly preferably not more than 7.5.

[0039] Process step (ii) - Activated zinc phosphate treatment:

[0040] According to the invention, in process step (ii), the zinc phosphate treatment of at least the zinc and / or iron surfaces of the series of components preactivated in process step (i) is carried out with an acidic aqueous composition, which then activates the growth of a very dense, closed but crystalline zinc phosphate layer, and for this purpose, like the aqueous dispersion in the preactivation, contains a dispersed particle component. In addition to this activated particle component (D), and a phosphate salt of a polyvalent metal cation selected at least in part from hopeite, phosphophyllite, scholzite and / or hallolite, wherein the acidic aqueous composition contains the following to form a zinc phosphate layer: (A) 5 to 50 g / kg of phosphate dissolved in water, calculated as PO4; (B) 0.3 to 3 g / kg zinc ions, and (C) free fluoride; The zinc phosphating composition is adjusted to have free acid at points greater than zero.

[0041] Thus, the acidic aqueous zinc phosphate treatment is provided to activate the growth of a crystalline phosphate coating on the surface of zinc and / or iron due to its particle component (D), and can therefore be obtained by appropriately adding a certain amount of aqueous dispersion to an acidic aqueous composition containing the above-mentioned components (A) to (C).

[0042] This aqueous dispersion, intended for addition to an acidic aqueous composition containing components (A) to (C), contains a particulate component (P) in water-dispersed form, at least one particulate inorganic compound (P1) composed of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and / or hallolite, and at least one polymeric organic compound (P2), The aqueous dispersion for providing the acidic aqueous composition for the zinc phosphating treatment in process step (ii) is preferably added in an amount such that the weight proportion of phosphate of the water-dispersed particulate component (D) of the acidic aqueous composition, each calculated as phosphate (PO), is at least 0.1 mg / kg, particularly preferably at least 0.5 mg / kg, very particularly preferably at least 1.0 mg / kg, and particularly preferably at least 2.0 mg / kg, of the acidic aqueous composition.

[0043] In a preferred embodiment, which allows a particularly resource-saving and economical operation of the process according to the invention, the series of components is contacted in step ii) of the process according to the invention with an acidic aqueous composition, which contains: (A) 5 to 50 g / kg of phosphate dissolved in water, calculated as PO4; (B) 0.3 to 3 g / kg zinc ions, and (C) free fluoride; having free acid at points greater than 0, The amount of the aqueous dispersion containing the particulate component (P) is 4.5 g / m on the hot-dip galvanized steel surface (Z) under the selected conditions of process step (ii) for zinc phosphate treatment. 2 Less than 4.0 g / m 2 less than 3.5 g / m 2 less than, very particularly preferably 3.0 g / m 2 is added continuously or discontinuously to the acidic aqueous composition in process step (ii) for zinc phosphate treatment, sufficient to maintain the properties of the acidic aqueous composition to deposit a zinc phosphate layer having a layer weight of less than The particle component (P) in the aqueous dispersion is at least one particulate inorganic compound (P1) composed of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and / or hallolite, and at least one polymeric organic compound (P2).

[0044] In this way, only the required amount of aqueous dispersion is added to the acidic aqueous composition for zinc phosphate treatment, and over-distribution is systematically avoided.

[0045] In a particularly preferred variant of the process according to the invention, in process step (i) for preactivation, an activation aid is dispensed into the acidic aqueous composition containing components (A) to (C) in the form of a wet film remaining on the component and introduced into the subsequent process step (ii) of the zinc phosphating treatment, in a quantity sufficient to bring the zinc and / or iron surface into contact with the component, so that the phosphate weight fraction of the water-dispersed particulate component (D), calculated in each case as phosphate (PO), of a phosphate of a polyvalent metal cation at least partially selected from hopeite, phosphophyllite, scholzite and / or hallolite, is at least 0.1 mg / kg, particularly preferably at least 0.5 mg / kg, very particularly preferably at least 1.0 mg / kg, and particularly preferably at least 2.0 mg / kg of the aqueous composition.

[0046] Alternatively, in an equally preferred variant, in the process step (i) for preactivation, a wet film is applied per component which remains on the component and is introduced into the subsequent process step (ii) of zinc phosphating, so that under the selected conditions of process step (ii) of zinc phosphating, a coating weight of 4.5 g / m 2 on the hot-dip galvanized steel surface (Z) is achieved. 2 Less than 4.0 g / m 2 less than 3.5 g / m 2 Less than, very particularly preferably, 3.0 g / m 2 An amount of activating co-agent sufficient to establish a minimum amount of water-dispersed particulate component (D) comprising a phosphate of a polyvalent metal cation selected at least in part from hopeite, phosphophyllite, scholzite, and / or hallolite in the acidic aqueous composition containing components (A)-(C) is dispensed for contact with the zinc and / or iron surface, sufficient to maintain the properties of the acidic aqueous composition to deposit a zinc phosphate layer at a layer weight of less than 1000 ppm.

[0047] In process step (ii), 4.5 g / m 2 Less than 4.0 g / m 2 less than 3.5 g / m 2 less than, very particularly preferably 3.0 g / m 2 The preferred property of the acidic aqueous composition for zinc phosphating according to the present invention, which results in the growth of a zinc phosphate layer on a hot-dip galvanized steel surface (Z) with a layer weight of less than 0.10 g / m² (hereinafter referred to as "phosphating quality"), should be checked on a cleaned and degreased (Z) substrate that has not been subjected to any further wet-chemical pretreatment steps or any rinsing steps before contacting it with the acidic aqueous composition of the process according to the present invention in step (ii) and after preactivation of the zinc surface in step (i). Cleaning and degreasing of the (Z) substrate occurs when the (Z) surface has a carbon coating of less than 0.10 g / m² of (Z) surface after cleaning and degreasing. The carbon layer thickness can be determined by pyrolysis. For this purpose, the (Z) substrate is brought to a substrate temperature (PMT) of 550°C in an oxygen atmosphere, and the amount of released carbon dioxide is quantitatively determined as the amount of carbon by an infrared sensor, for example, by an analytical device such as the LECO® RC-412 Multiphase Carbon Determinator (Leco Corp.).

[0048] Therefore, to confirm the phosphate treatment quality of the acidic aqueous composition, hot-dip galvanized steel (Z) was treated with deionized water (κ<1 μS cm -1 The substrate (Z) is first cleaned by immersion for 5 minutes at pH 11.0 and 55°C using an alkaline cleaner formulated as 2 wt% Bonderite® C-AK 1565 A and 0.2 wt% Bonderite® C-AD 1270 in HCl (HCl 3.0). The thus cleaned and degreased substrate (Z) is then washed with deionized water (κ<1 μS cm) at room temperature. -1), and then supplied to the treatment stage according to process steps (i) and (ii) according to selected process conditions. "According to selected process conditions" means that the temperature, application duration and bath circulation are the same, and a wet chemical treatment stage is used which is intended for the phosphating quality specified as preferred according to the invention, i.e., the resulting target layer weight on the hot-dip galvanized steel (Z) is 4.5 g / m 2 Less than 4.0 g / m 2 less than 3.5 g / m 2 less than, very particularly preferably 3.0 g / m 2 This means that the phosphating quality is less than 0.05%. Therefore, in the present process according to the invention, the phosphating quality can be determined by introducing a cleaned and degreased sheet of hot-dip galvanized steel (Z) together with a series of components for process steps (i) and (ii), and the layer weight of zinc phosphate on the sheet, and therefore the phosphating quality of the acidic aqueous composition for zinc phosphating, is then determined in process step (ii). It should be noted that the outer surface of such a test sheet metal to be phosphating in process step (i) has formed a complete liquid film containing the aqueous dispersion before coming into contact with the acidic aqueous composition in process step (ii).

[0049] In its role as a test sheet for determining phosphating quality, the cleaned and degreased sheet of hot-dip galvanized steel (Z) is preferably firmly connected to the component or transport frame to ensure that the flow conditions during transport of the component with the transport frame through the phosphating bath are reproduced as closely as possible for the test sheet. For this purpose, the test sheet should ideally be connected to the component or transport frame so that transporting the test sheet with the component and transport frame does not affect the considered flow conditions compared to transporting the component and transport frame without such a test sheet, and the flow conditions are substantially identical in both cases and therefore substantially correspond to the flow conditions of at least a portion of the series of components. This can be achieved, for example, by adapting the size and / or shape of the test sheet to the size and shape of the component and / or transport frame that will be placed adjacent to the test sheet in each case. In this case, particularly when the test sheet is placed on the outer surface portion of the component or transport frame, it is conceivable that the dimensions of the test component will be correspondingly smaller than the dimensions of the surface portion, for example, to prevent the test component from protruding beyond the surface portion. Alternatively or additionally, the test component may follow the curvature or other planar deviation of the surface portion or the carrier frame. It has been found to be particularly advantageous to select a sheet portion that is sufficiently small compared to the size of the relevant outer surface of the component, which is particularly suitable when the outer surface is placed in a position where it has a particularly low curvature or in a position where it has the lowest curvature of the component, and the test sheet metal is then mounted substantially parallel to and spaced apart along the surface normal of such outer surface.It is particularly useful and preferred if the test sheet metals are spaced along a surface perpendicular to the zinc and / or iron surface of the component, in order to ensure in the simplest way that the liquid film containing the aqueous dispersion dispensed in process step (i) for contact with said surface can be applied without the need for complex adaptations of the device for dispensing the aqueous dispersion in process step (i).

[0050] The phosphate treatment quality is obtained directly during the treatment of such components which also have a hot-dip galvanized steel (Z) surface as a zinc surface, which is also preferred in a preferred embodiment of the process according to the invention.

[0051] If the contact is extended for 1 minute, the increase in layer weight on hot-dip galvanized steel (Z) is 0.2 g / m 2 and therefore it is further preferred for the quality of the phosphating that the layer formation under the selected conditions is already within the self-limiting range so as to ensure the properties of the acidic aqueous composition for zinc phosphating to produce a dense crystalline zinc phosphate layer in step (ii) of the process according to the invention. Thus, in the zinc phosphating process step, under the selected conditions of the zinc phosphating process step in the process according to the invention, a zinc phosphate layer of 4.5 g / m on the hot-dip galvanized steel surface (Z) is obtained. 2 Less than 4.0 g / m 2 less than 3.5 g / m 2 less than, very particularly preferably 3.0 g / m 2 Preferably, an aqueous dispersion containing a particulate component (P) is added in an amount sufficient to maintain the properties of the acidic aqueous composition to deposit a zinc phosphate layer having a layer weight of less than 0.2 g / m when the contact time with the acidic aqueous composition is extended to 60 seconds, and the layer weight increase achieved under the conditions selected in process step (ii) of the zinc phosphate treatment in the process according to the invention is less than 0.2 g / m when the contact time with the acidic aqueous composition is extended to 60 seconds. 2 does not exceed.

[0052] Typically, the phosphating quality is determined and monitored in the preferred process according to the present invention by subjecting hot-dip galvanized steel (Z) that has been cleaned and degreased as described above, subjected to zinc phosphating process steps at regular intervals during the course of processing, and then subjected to layer weight determination. As already mentioned, the phosphating quality is obtained directly during the course of processing of such components that also have at least one surface of hot-dip galvanized steel (Z) in addition to the zinc surface. As long as the metered addition of the aqueous dispersion ensures the phosphating quality of the acidic aqueous composition, a homogeneous, closed, dense, crystalline zinc phosphate coating is deposited on the course of components with surfaces consisting of metallic zinc and / or iron within a typical processing time of 20 seconds to 5 minutes.

[0053] The layer weight of zinc phosphate was determined by zinc phosphate treatment and deionized water (κ<1 μS cm -1 The zinc phosphate layer weight is determined within the scope of the present invention by removing the zinc phosphate layer using a 5 wt. % CrO3 aqueous solution as a pickling solution, which is brought into contact with a defined area of ​​the phosphated material or component for 5 minutes at 25°C immediately after rinsing with 0.1% CrO3, followed by determining the phosphorus content in the same pickling solution by ICP-OES. The zinc phosphate layer weight can be determined by multiplying the surface area related amount of phosphorus in grams / square meter by a factor of 6.23.

[0054] The addition of an aqueous dispersion containing particulate component (P) to the acidic aqueous composition for the zinc phosphate treatment process is carried out in the process according to the present invention with the aim of maintaining the phosphating quality in process step (ii). To maintain the phosphating quality throughout the treatment process, the addition can be carried out by continuous or discontinuous metered addition to the zinc phosphating system tank. Continuous metered addition is preferred, as components are pretreated directly in succession, allowing the decrease in phosphating quality per time interval to be determined with sufficient accuracy, so that the amount of activator can be continuously added by metering to compensate for the loss in performance. This process has the advantage that after starting up the pretreatment line and determining the material flow for the metered addition of the aqueous dispersion and other active components, no further checks of the phosphating quality are necessary, as long as the treatment process remains unchanged in terms of the timing and quality of the treated components and the treatment parameters in process step (ii) for the zinc phosphating treatment. However, if the system does not guarantee or require a constant operating mode during the treatment process, discontinuous metered addition of the aqueous dispersion containing particulate component (P) is advantageous and may even be recommended. In this case, the phosphating quality of the acidic aqueous composition in step (ii) is preferably monitored continuously or at defined time intervals, and then the layer weight on the hot-dip galvanized steel (Z) is 4.5 g / m 2 Less than 4.0 g / m 2 less than 3.5 g / m 2 less than, very particularly preferably 3.0 g / m 2When a specific value below 0.05 is no longer reached, a specific amount of activation aid is metered in. Continuous or quasi-continuous determination of phosphating quality at specified time intervals can also be performed using proxy data that correlates with the actual zinc phosphate layer weight. Non-destructive determination of layer thickness using, for example, eddy current processes or non-contact optical determination methods such as ellipsometry or spectroscopic reflectometry provides suitable proxy data for zinc phosphate layer weight. This data can be reliably measured on the zinc surface of components in pretreatment lines and correlated with the actual layer weight on the hot-dip galvanized steel part (Z). Higher layer weights on hot-dip galvanized steel (Z) are associated with a lower crystallite number density, but because the crystallites are relatively large, roughness increases with layer weight. Therefore, determining crystallite size, and therefore roughness, by optical profilometry can also provide proxy data for layer weight.

[0055] It has been found that the phosphating quality is already sufficiently adjusted in most cases when an aqueous dispersion containing particulate component (P) for activating the zinc phosphating composition is added continuously or discontinuously in an amount suitable for producing a stable amount of phosphate contained in the water-dispersed particulate component (D) in the acidic aqueous composition (calculated in each case as the amount of phosphate (PO4) and with respect to the acidic aqueous composition during the pretreatment of the series of components) of preferably at least 0.1 mg / kg, particularly preferably at least 0.5 mg / kg, particularly preferably at least 1.0 mg / kg. This applies in particular to contacting the components by immersion in a zinc phosphating system tank containing the acidic aqueous composition.

[0056] In conjunction with process step (i), which results in the preactivation of the zinc and / or iron surfaces, the activated zinc phosphating of step (ii) can be carried out in a particularly resource-efficient manner, significantly reducing the consumption of active ingredients without losing phosphating quality. This applies not only to the addition rate of the aqueous dispersion containing the particulate component (P), but also to the consumption of the active components (A) to (C) of the acidic aqueous zinc phosphating composition, due to the superior phosphating quality achieved on the zinc and / or iron surfaces.

[0057] With regard to the acidic aqueous composition for zinc phosphating, for the formation of a homogeneous and closed zinc phosphate layer, it is essential in step (ii) of the process according to the invention that said composition contains at least: (A) 5 to 50 g / kg of phosphate dissolved in water, calculated as PO4; (B) 0.3 to 3 g / kg zinc ions, and (C) free fluoride; and free acid at points greater than 0.

[0058] In this context, the amount of phosphate ions includes orthophosphoric acid and the anions of salts of orthophosphoric acid dissolved in water, calculated as PO4.

[0059] The proportion of free acid at a point in the acidic aqueous composition for the zinc phosphate treatment in step (ii) of the process according to the invention is preferably greater than 0.5, particularly preferably greater than 0.8, very particularly preferably greater than 1.0, but preferably not greater than 3.0, particularly preferably not greater than 2.0. The proportion of free acid at a point is determined by diluting a 10 ml sample volume of the acidic aqueous composition to 60 ml and titrating it to a pH value of 3.6 with 0.1 N sodium hydroxide solution. The consumption of ml of sodium hydroxide solution indicates the number of points of free acid.

[0060] The pH of the acidic aqueous composition is preferably usually less than 3.6, particularly preferably less than 3.4, very particularly preferably less than 3.2, but preferably greater than 2.5, particularly preferably greater than 2.7. The "pH value" 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 a pH-sensitive glass electrode.

[0061] A certain amount of free fluoride or a source of free fluoride ions is essential for the layer-forming zinc phosphating process.For example, in the zinc phosphating of an automobile body that is at least partially made of aluminum, as long as components that include iron or aluminum surfaces in addition to zinc surfaces are zinc phosphating to form a layer, it is advantageous for the amount of free fluoride in the acidic aqueous composition in step (ii) to be at least 10 mg / kg, particularly preferably at least 40 mg / kg.The concentration of free fluoride should not exceed a value that shows a loose adhesion of the phosphate coating that can be easily wiped off.For this reason, it is advantageous and therefore preferred that the concentration of free fluoride in the acidic aqueous composition for zinc phosphating in step (ii) of the process according to the present invention is less than 300 mg / kg, particularly preferably less than 250 mg / kg, particularly preferably less than 200 mg / kg.

[0062] The amount of free fluoride should be determined potentiometrically using a fluoride-sensitive measuring electrode in the relevant acidic aqueous composition at 20°C after calibration with a fluoride-containing buffer solution 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 dissolved in deionized water (κ<1 μS cm ) at 60°C. -1A substance is water-soluble within the meaning of the present invention if its solubility in water (calculated as F) is at least 1 g / L.

[0063] In order to suppress what is known as "pinholing" on the surface of metal materials made of zinc, it is preferred in such a process according to the invention that the source of free fluoride in step (ii) is at least partly selected from complex fluorides of element Si, in particular hexafluorosilicic acid and its salts. The term pinholing will be 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.

[0064] In the process according to the present invention, accelerators known in the prior art can be added to the acidic aqueous composition to increase the layer formation rate. These accelerators are preferably selected from 2-hydroxymethyl-2-nitro-1,3-propanediol, nitroguanidine, N-methylmorpholine-N-oxide, nitrites, hydroxylamine, and / or hydrogen peroxide. When nitroguanidine or hydroxylamine is used as an accelerator, a relatively low metered addition of an aqueous dispersion containing the water-dispersed particle component (P) is required to provide the acidic aqueous composition, or a lower constant amount of the water-dispersed particle component (P) must be maintained in the acidic aqueous composition for the zinc phosphate treatment process in step (ii). As a result, from the viewpoint of particularly low material usage to maintain the quality of the phosphate treatment, nitroguanidine or hydroxylamine, especially nitroguanidine, is found to be particularly preferred as an accelerator in the acidic aqueous composition in step (ii) of the process according to the present invention.

[0065] The embodiment in which less than 10 ppm in total of nickel and / or cobalt ions are present in the acidic aqueous composition for the zinc phosphating treatment in step (ii) of the process according to the invention is particularly preferred from an ecological point of view.

[0066] Additionally, the process according to the present invention may also employ additives known in the art in zinc phosphate treatment processes.

[0067] Preferred embodiments of the aqueous dispersion used in step (ii) according to the present invention and containing the water-dispersed particle component (P) can be found in particular in the description of suitable activating coagents.

[0068] Suitable activating agent

[0069] The definitions and preferred specifications set forth below apply to the dispersed particle component (P) and at least one particulate inorganic compound (P1) or polymeric organic compound (P2) in the aqueous dispersion, regardless of whether the dispersed particle component (P) is a component of the aqueous pre-activation dispersion in process step (i) or a component of the aqueous dispersion that provides the self-activating acidic aqueous composition for zinc phosphating in process step (ii). For simplicity, hereinafter, reference will be made only to the "activation coagent" instead of the respective "aqueous dispersion containing dispersed component (P)." Preferred activating coagents have high stability against agglomeration and are therefore particularly suitable for the formation of crystalline phosphate coatings. When used in this manner, they are characterized by releasing or providing a high proportion of activated phosphate particles for activation of the zinc and / or iron surface, thereby enabling dense, closed, crystalline coatings with relatively low layer weights to be achieved particularly reliably in the process according to the invention.

[0070] The activation co-agent used in accordance with the present invention, i.e., the activation co-agent used for preactivation in step (i) and for maintaining the phosphating quality or for providing an acidic aqueous composition for the zinc phosphating treatment in step (ii), is therefore an aqueous dispersion containing, in water-dispersed form, a particulate component (P) comprising at least one particulate inorganic compound (P1) composed of a phosphate salt of a polyvalent metal cation selected at least in part from hopeite, phosphophyllite, scholzite and / or hallolite, and at least one polymeric organic compound (P2).

[0071] The use of polyvalent metal cations in the form of phosphates is responsible for good (pre)activation performance, and therefore should be contained in the activating aid in a sufficiently high proportion in the dispersed particulate component (P). The proportion of phosphates contained in the particulate inorganic compound (P1) is therefore preferably at least 25% by weight, particularly preferably at least 35% by weight, particularly preferably at least 40% by weight, and very particularly preferably at least 45% by weight, based on the dispersed inorganic components of the activating aid.

[0072] The dispersed particle component (P) of the activation aid—or the water-dispersed particle component (D) of the acidic aqueous composition in step (ii)—is the solids remaining after drying the retentate from ultrafiltration of a defined partial volume of the activation aid—or the acidic aqueous composition—with a nominal cutoff of 10 kD (NMWC, nominal molecular weight cutoff). 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 supplied. The inorganic particle component of the activation aid—or the inorganic water-dispersed particle component of the acidic aqueous composition in step (ii)—is similarly the one remaining when the particle component (P) or (D) obtained from drying the ultrafiltration retentate is pyrolyzed in a reactor by supplying a CO2-free oxygen stream at 900°C without adding a catalyst or other additives until the infrared sensor provides a signal at the reactor outlet identical to that of the CO2-free carrier gas (blank value). The phosphate contained in the corresponding inorganic particle component, calculated as PO4, is determined by atomic emission spectrometry (ICP-OES) after acid digestion with 10 wt% HNO3 aqueous solution at 25°C for 15 minutes, directly from the acid digestion process, as the phosphorus content multiplied by a factor of 3.07.

[0073] As already mentioned, the active component of the activator is primarily composed of phosphates, which are 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, and very particularly preferably at least partially selected from hopeite. The achievement of the desired phosphating quality on the zinc and / or iron surface in the process according to the invention is essentially based on the phosphates contained in particulate form in the activator. Without taking into account water of crystallization, hopeite stoichiometrically contains 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 consists of Zn2Ca(PO4)3, and hallolite consists of Mn3(PO4)2. The presence of hopeite, phosphophyllite, scholzite and / or hallolite crystalline phases in the activated co-agent can be demonstrated by separation of the particle component (P) by ultrafiltration with a nominal cut-off limit of 10 kD (NMWC: nominal molecular weight cut-off) as described above and X-ray diffractometry (XRD) after drying of the retentate to constant mass at 105°C.

[0074] Since the presence of a phosphate containing zinc ions and having a particular crystallinity is preferred, in the process according to the invention it is preferred that the activating agent contains at least 20% by weight, particularly preferably at least 30% by weight, particularly preferably at least 40% by weight of zinc in the inorganic particulate component, calculated as PO, based on the phosphate content of the inorganic particulate component, in order to form a strongly adhering crystalline zinc phosphate coating.

[0075] However, the activating agent is preferably not intended to further contain titanium phosphates, because although they can also have an activating effect themselves, they do not have any additional positive effect on the phosphating quality within the context of the present invention. Thus, in a preferred embodiment of the process according to the invention, the proportion of titanium in the inorganic particle component of the activating agent is less than 0.01% by weight, particularly preferably less than 0.001% by weight, based on the activating agent. In a particularly preferred embodiment, the activating agent contains a total of less than 10 mg / kg, particularly preferably less than 1 mg / kg, of titanium.

[0076] The polymeric organic compound (P2) that stabilizes the particle component (P) of each dispersion significantly influences the effectiveness of the activation coagent. The choice of polymeric organic compound appears to be critical to the degree of preactivation of the zinc and / or iron surfaces in process step (i) and the phosphating quality ultimately achieved through integrated activation in step (ii).

[0077] 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 the relevant reference size, 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 by computer according to the strip method using a third-order calibration curve. Hydroxylated polymethacrylate is a suitable 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 a suitable eluent.

[0078] Particularly efficient activating coagents which are preferably used in the process according to the invention are present when the polymeric organic compound (P2) used to disperse the particulate inorganic compound (P1) is at least partially composed of styrene and / or α-olefins having not more than 5 carbon atoms, and the polymeric organic compound (P2) further comprises units of maleic acid, its anhydride and / or its imide, preferably further comprising polyoxyalkylene units, particularly preferably polyoxyalkylene units, in its side chain.

[0079] 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 will be clear to those skilled in the art that the polymeric organic compound (P2) contains these monomers as structural units in unsaturated form, covalently bonded to each other or to other structural units.

[0080] A preferred co-activator comprises a polymeric organic compound (P2) composed at least in part of styrene.

[0081] The polymeric organic compound (P2) used for colloidal stabilization of the particle component (P) of the activating agent preferably contains polyoxyalkylene units of 1,2-ethanediol and / or 1,2-propanediol, particularly preferably both 1,2-ethanediol and 1,2-propanediol. The proportion of 1,2-propanediol in the total polyoxyalkylene units is preferably at least 15% by weight, particularly preferably not more than 40% by weight, based on the total polyoxyalkylene units. It is also preferred that the polymeric organic compound (P2) contains polyoxyalkylene units in its side chains. The proportion of polyoxyalkylene units in the total polymeric organic compound (P2) is preferably at least 40% by weight, particularly preferably at least 50% by weight, particularly preferably not more than 70% by weight, which is advantageous for the dispersibility of the compound.

[0082] In order to fix the polymeric organic compound (P2) to the inorganic particulate component (P1) of the activating aid formed from polyvalent metal cations in the form of phosphates at least partially selected from hopeite, phosphophyllite, scholzite and / or hallolite, and to increase the stability and ability of the particulate component (P) to activate the surface of zinc and / or iron, the organic polymer compound (P2) also particularly preferably has imidazole units in the side chains of the polymer compound (P2).

[0083] In a preferred embodiment, the amine value of the organic polymer compound (P2) 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. Therefore, in a preferred embodiment, the total polymeric organic compounds in the particle component (P) of the activating coagent also have these preferred amine values. The amine value is determined by weighing approximately 1 g of the relevant reference size-organic polymer compound (P2) or all of the polymeric organic compounds in the particle component (P) 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 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) of the weight corresponds to the amine value in milligrams of KOH per gram of the relevant reference value.

[0084] To ensure a sufficient number of polyoxyalkylene units, it has also proven advantageous for the polymeric organic compounds (P2), preferably also the total polymeric organic compounds in the particulate component (P), to have an acid number according to DGF CV 2(06) (as of April 2018) of at least 25 mg KOH / g, but preferably less than 100 mg KOH / g, particularly preferably less than 70 mg KOH / g. Preferably, the polymeric organic compounds (P2), preferably also the total polymeric organic compounds in the particulate component (P), have a hydroxyl number of less than 15 mg KOH / g, particularly preferably less than 12 mg KOH / g, more particularly preferably less than 10 mg KOH / g, in each case measured according to method A of European Pharmacopoeia 9.0 01 / 2008:20503.

[0085] Suitable commercially available representatives of polymeric organic compounds (P2) 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.

[0086] For a stable dispersion of the inorganic particle component in the activating coagent, it is sufficient that the proportion of polymeric organic compounds (P2) relative to the particle component (P), preferably the total proportion of polymeric organic compounds in the particle component (P), is at least 3% by weight, particularly preferably at least 6% by weight, but preferably does not exceed 15% by weight.

[0087] The activation aid preferably contains no more than 40% by weight of particulate component (P) based on the agent, because otherwise the stability of the dispersion and the process operability in process step (i) for preactivation by wetting using a spray device and process step (ii) for metering the agent into the acidic aqueous composition for zinc phosphate treatment using a metering pump are no longer guaranteed or are at least complicated. According to the present invention, it has been shown that the use of an activation aid containing at least 5% by weight, but particularly preferably no more than 30% by weight, of particulate component (P) based on the agent for metering into the acidic aqueous composition in process step (ii) achieves both good storage and applicability. However, the activation aid used in process step (i) as an aqueous dispersion for wetting zinc and / or iron surfaces should preferably not be too concentrated for wetting by misting, preferably containing no more than 5% by weight of particulate component (P), while the agent preferably contains at least 0.005% by weight of particulate component (P) based on the agent for good activation.

[0088] In concentrated aqueous dispersions, i.e., in activating coagents having a proportion of particle component (P) of at least 5% by weight relative to the drug, the drug can further be characterized by its D50 value of more than 10 μm, which is correspondingly preferred. However, for good applicability, particularly in process step (i), it is preferred that the aqueous dispersion of particle component (P) has a D90 value of less than 150 μm, preferably less than 100 μm, and in particular less than 80 μm. In the context of the present invention, the D50 or D90 value refers to the particle size of not more than 50% or 90% by volume of the particle components contained in the aqueous dispersion, respectively. According to ISO 13320:2009, the D50 or D90 value is determined immediately after dilution of the activating coagent to 0.05% by weight of the dispersed particle component, using a refractive index of spherical and scattering particles, nD=1.52-i·0.1, in a corresponding amount of deionized water (κ<1 μS cm) at 20 °C. -1 The particle size distribution can be determined from the volume-weighted cumulative particle size distribution by scattered light analysis according to Mie theory using the activating co-agent. The dilution is performed by adding an amount of activating co-agent equivalent to a volume of 200 ml of deionized water to the sample container of a Horiba Ltd. LA-950 V2 particle size analyzer, where it is mechanically circulated into the measurement chamber (the circulation pump is set to 1167 rpm with a volumetric flow rate of 3.3 liters / min on the LA-950 V2: level 5). The particle size distribution is measured within 120 seconds after the activating co-agent has been added to the dilution volume.

[0089] The presence of a thickener can be advantageous in preventing irreversible aggregation of the primary particles of the particulate component (P), particularly when the activator contains at least 5% by weight of the particulate component (P) relative to the drug, as described above. Therefore, the activator preferably contains a thickener in an amount that provides the activator with a maximum dynamic viscosity of at least 1000 Pa·s, preferably less than 5000 Pa·s, at 25°C in the shear rate range of 0.001 to 0.25 inverse seconds. This preferably provides shear-thinning behavior, i.e., a decrease in viscosity with increasing shear rate at 25°C and at shear rates above that present at the maximum dynamic viscosity, thereby providing the activator with thixotropic flow behavior throughout. 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.

[0090] Within the meaning of the present invention, the thickener is deionized water (κ<1 μS cm ) at a temperature of 25°C. -1 A polymeric compound or mixture of defined compounds 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 as a 0.5% by weight component in a 2000 sieve. To determine its thickening properties, a mixture with water should be prepared by adding the corresponding amount of polymeric compound to the aqueous phase at 25°C while stirring, then removing air bubbles from the homogenized mixture in an ultrasonic bath and leaving it for 24 hours. The viscosity reading is then taken within 5 seconds of applying a shear rate of 60 rpm using a size 2 spindle.

[0091] The activating co-agent preferably contains one or more thickeners in a total amount of at least 0.5% by weight, but preferably not more than 4% by weight, particularly preferably not more than 3% by weight, and the total proportion of polymeric organic compounds in the non-particulate component of the activating co-agent more preferably not more than 4% by weight (relative to the drug). The non-particulate component is the solids content of the activating co-agent in the relevant aqueous dispersion after drying to constant mass at 105°C or in the permeate of the above-mentioned ultrafiltration, i.e., the solids content after the particulate component has been separated by ultrafiltration.

[0092] Certain classes of polymeric compounds are particularly suitable thickeners and are readily commercially available.Thus, the thickener is preferably selected from polymeric organic compounds, preferably selected from polysaccharides, cellulose derivatives, aminoplasts, polyvinyl alcohols, polyvinylpyrrolidones, polyurethanes and / or urea-urethane resins, particularly preferably urea-urethane resins, in particular urea-urethane resins, which are mixtures of polymeric compounds resulting from the reaction of polyhydric isocyanates with polyols and mono- and / or diamines. 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 preferably consist of at least 6, particularly preferably at least 8, more particularly preferably at least 10, but preferably less than 26, particularly preferably less than 23 oxyalkylene units.

[0093] A particularly suitable and therefore preferred urea-urethane resin 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 without free or blocked isocyanate groups are particularly preferred. As a component of the activator, such urea-urethane resins promote the formation of loose aggregates of primary particles that are protected from further aggregation and dissociate into primary particles upon dilution during contact in step (i) or upon addition to the acidic aqueous composition in step (ii). To further enhance this property profile, it is preferred that a urea-urethane resin without free or blocked isocyanate groups or terminal amine groups be used as a thickener. Thus, in a preferred embodiment, the thickener, 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 even more particularly preferably less than 2 mg KOH / g, as determined in each case according to the method described above for the organic polymeric compound (P2). Because the thickener is substantially dissolved in the aqueous phase of the activator and can therefore be allocated to the non-particulate component, while component (P2) is substantially bound to the particulate component (P), activator co-agents are preferred in which the total polymeric organic compound in the non-particulate component has an amine value of less than 16 mg KOH / g, particularly preferably less than 10 mg KOH / g, and even more 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 measured 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, in each case determined experimentally as described above in connection with the definition according to the invention of polymeric organic compounds, are advantageous according to the invention and are therefore preferred.

[0094] The coactivator preferably has a pH value in the range of 6.0 to 9.0, particularly preferably a pK of less than 6. S pK value or less than 5 B The aqueous dispersion does not contain a pH-adjusting water-soluble compound having a pH value.

[0095] The activation aid may also contain an adjuvant selected from, for example, a preservative, a wetting agent, and an antifoaming agent, in an amount necessary for the relevant function. The proportion of other compounds in the non-particulate component that are not adjuvants, particularly preferably thickeners, is preferably less than 1% by weight.

[0096] The co-activator is preferably a) obtaining a pigment paste by triturating 10 parts by weight of an inorganic particulate compound (P1) with 0.5 to 2 parts by weight of a polymeric organic compound (P2) 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 from Malvern Panalytical GmbH, until a D50 value of less than 1 μm is reached, as measured by dynamic light scattering; b) The pigment paste is dissolved in an amount of water, preferably deionized water (κ<1 μS cm -1 ) or by dilution with tap water and thickener to provide a dispersed particle component (P) of at least 5% by weight and a maximum dynamic viscosity of at least 1000 Pa·s at a temperature of 25°C in a shear rate range of 0.001 to 0.25 inverse seconds, Preferred embodiments of the co-activators are obtained in an analogous manner by selecting the corresponding components (P1), (P2) and thickeners in the amounts that may be provided or required in each case.

[0097] In the context of the present invention, particularly for reasons of process economy, it is preferred that the activating coagents in process steps (i) and (ii) are each based on the same water-dispersed particle component (P). The water-dispersed particle components (P) are already considered to be identical if components (P1) and (P2) do not differ from each other in terms of their chemical constitution, i.e., if the water-dispersed particle components (P) of each aqueous dispersion contain stoichiometrically identical phosphate salts of the same polyvalent cations and the same constitutional repeating units for the polymeric organic compound.

[0098] Exemplary embodiments: The following is intended to demonstrate that wetting the metal substrate with an activating co-agent prior to the activated zinc phosphating process can reduce the layer weight while simultaneously saving on the amount of activating co-agent required to set up the activated zinc phosphating bath.

[0099] For this purpose, test sheet metals (105 × 190 mm, Gardobond® from Chemetall) made of cold-rolled steel (CRS), hot-dip galvanized (HDG) steel and aluminium (alloy AA6014) were first wetted with the activation co-agent and immediately zinc phosphated, respectively.

[0100] The process sequence listed and performed in Table 1 provides the following processing steps (1) to (6): (1) Spray degreasing at 1.0 bar for 60 seconds at a spray medium temperature of 54°C (the spray medium had a pH value of 11.2 and consisted of the following): 30g / kg Bonderite® C-AK 1574 A 3g / kg Bonderite® C-AD 1270 1g / kg Bonderite® M-AD 100 All products are manufactured by Henkel AG & Co. KGaA Amount of NaHCO3 to set pH Remainder: deionized water (κ<1 μS cm -1 ) (2) Immersion degreasing at an immersion medium temperature of 55°C for 180 seconds (the immersion medium with a pH value of 11.2 had the same composition as the spray degreasing medium (1)). (3) Rinse with deionized water (κ<1 μS cm ) at a medium temperature of approximately 20°C for approximately 60 seconds. -1 ) and rinse (4) Wet activation by misting the test sheet metal at about 20°C with an activation aid having a pH value of 10.0 and consisting of: 0.3 g / kg (a), 0.5 g / kg (b), or 3.0 g / kg (c) Bonderite® M-AC AC 3000 (Henkel AG&Co KGaA) 10% by weight of NaOH solution to set the pH Remainder: deionized water (κ<1 μS cm -1 ) Inorganic particle component (P1): Hopeite (Zn3(PO4)2) Polymeric organic compound (P2): Maleic acid-styrene copolymer modified with EO / PO units Amount of particle component (P) in the activation aid: 60 mg / kg (a), 100 mg / kg (b), or 600 mg / kg (c) Misting was carried out using a spray bottle (manufactured by Wurth; item no. 0891 502 002; 500 ml); three bursts of spray on each side of the sheet were sufficient to thoroughly wet the surface. The sheet thus wetted was then immersed in the zinc phosphate treatment bath from step (5) after activating the spray for approximately 5 seconds. (5) Activated trication zinc phosphate treatment by immersion in a phosphating bath at 51°C for 180 seconds, where the phosphating bath had 1.1 points free acid, 26.5 points total acid, and 170 mg / kg free fluoride and had the following composition: 1.3g / kg zinc ions 0.8g / kg manganese ions 0.9g / kg nickel ions 14.7g / kg phosphate anion 1.0g / kg SiF6 anion 1.3g / kg NaNO3 1.0 g / kg hydroxylamine Amount of added activation agent: deionized water (κ<1 μS cm -1 1.0 g / kg (a) or 0.2 g / kg (b) Bonderite® M-AC 3000 (manufactured by Henkel AG & Co. KGaA) Amount of water-dispersible particle component (D): 200 mg / kg (a) or 40 mg / kg (b) (6) Rinse with deionized water (κ<1 μS cm ) at a medium temperature of approximately 20°C for approximately 60 seconds. -1 ) and rinse (7) Drying the sheet by blowing compressed air on it.

[0101] Table 1 lists each of the layer weights achieved following the process sequence listed in the table. It can be seen that preactivation of the zinc surface results in a significant layer weight reduction in the activated zinc phosphate treatment process (V1 vs. E1), which occurs already during misting using a low concentration aqueous dispersion for activation wetting. A 10-fold increased concentration results in a layer weight reduction of approximately 2 g / m 2 A further layer weight reduction of 100g / m occurs on the zinc surface, still achieving a closed and homogeneous phosphate layer (E1 vs. E2). Even on the steel surface, preactivation by misting again significantly reduces the layer weight, which is already 3g / m without preactivation. 2 (CRS:V1) and 2 g / m without losing phosphate treatment quality during layer formation. 2 The layer formation process on the aluminum surface only slightly depends on the corresponding process sequence, and is reduced to values ​​below 2 g / m with or without preactivation. 2 Overall, the process according to the invention still allows different layer weight coatings to be levelled on different substrates during activated zinc phosphate treatment. For components made of zinc, iron and aluminium, a coating weight of 2 g / m2 or more is achieved after activated zinc phosphate treatment on all substrates. 2Simply wetting the zinc or zinc and iron surface with the activating agent is sufficient to obtain a closed, homogeneous, crystalline zinc phosphate coating with a layer weight in the region of 0.25 mm. The two-step process is also highly effective in terms of activating agent use and can be optimized to require less activating agent overall compared to a simple activated zinc phosphate treatment, as demonstrated by the process sequence according to Type E3. Thus, in the process sequence according to Type E3, the amount of activating agent in the zinc phosphate bath can be reduced to one-fifth of the amount in Process Sequence V1, while still achieving significantly lower layer weights on HDG. Only preactivation of the zinc surface is required, and therefore only a portion of the activating agent, which would otherwise need to be added to the zinc phosphate bath in the process sequence according to Type V1, is required to maintain phosphating quality. It should also be noted that some of the activating agent remaining on the preactivated zinc surface enters the zinc phosphate bath directly, along with components that contribute to maintaining phosphating quality. Therefore, overall, the process according to the present invention makes available a highly resource-efficient zinc phosphating process. [Table 1]

Claims

1. 1. A process for the anti-corrosion pretreatment of a series of a plurality of components, each component of said series having at least partly a zinc and / or iron surface, which is first subjected to a process step (i) for activating the zinc and / or iron surface, and which immediately after a process step (ii) for zinc phosphating, In process step (i), at least the zinc and / or iron surface of each of the series of components is treated with a water-dispersed particle component (P) at least one particulate inorganic compound (P1) composed of a phosphate of a polyvalent metal cation at least partly selected from hopeite, phosphophyllite, scholzite and / or hallolite, and at least one polymeric organic compound (P2) contacting the aqueous dispersion containing said contacting being effected by dispensing said aqueous dispersion from a source such that no more than 1.00 liters of said aqueous dispersion is dispensed into contact with said dispersion per square meter of said surface of each component in said series, preferably per square meter of said zinc and / or iron surface of each component in said series; In process step (ii), at least the zinc and / or iron surface of each component in the series is contacted with an acidic aqueous composition having free acid at a point greater than 0; (A) PO ４ 5-50 g / kg of phosphate dissolved in water, calculated as (B) 0.3 to 3 g / kg of zinc ions; (C) free fluoride, and (D) a water-dispersed particulate component comprising a phosphate salt of a polyvalent metal cation, wherein the phosphate salt is at least partially selected from hopeite, phosphophyllite, scholzite, and / or hallolite; The acidic aqueous composition is obtained by adding a certain amount of an aqueous dispersion to the acidic aqueous composition containing the components (A) to (C), and the aqueous dispersion contains a water-dispersed particle component (P), which is at least one particulate inorganic compound (P1) composed of phosphates of polyvalent metal cations at least partly selected from hopeite, phosphophyllite, scholzite and / or hallolite, and at least one polymeric organic compound (P2).

2. 2. A process according to claim 1, characterized in that the process of contacting at least the zinc and / or iron surfaces of the components with the dispersion in process step (i) is carried out by dispensing the aqueous dispersion from a source in such a way that not more than 0.50 litres, preferably not more than 0.20 litres, of the aqueous dispersion is dispersed per square metre of the zinc and / or iron surfaces of the series of components to be activated that are brought into contact with the dispersion, preferably per square metre of the surfaces of the series of components.

3. 3. The process according to claim 1, wherein the aqueous agent brought into contact with the surface in process step (i) is dispensed in such a way that at least the zinc and / or iron surface is covered with a liquid film containing the aqueous dispersion, resulting in a volume-related coating of preferably not more than 1.00 liters, particularly preferably not more than 0.50 liters, very particularly preferably not more than 0.20 liters, and particularly preferably not more than 0.10 liters per square meter on the zinc and / or iron surface.

4. 4. The process according to claim 1, wherein the aqueous medicament is dispensed in process step (i) as a spray, as a spray mist or as a liquid film, preferably as a spray and / or a spray mist, particularly preferably as a spray mist.

5. 5. The process according to claim 1, wherein in process step (i) and / or process step (ii), the polymeric organic compound (P2) in the particulate component (P) of the aqueous dispersion is at least partially composed of styrene and / or α-olefins having not more than 5 carbon atoms, and the polymeric organic compound (P2) further comprises units of maleic acid, its anhydrides and / or imides in its side chains, preferably further comprising polyoxyalkylene units, particularly preferably polyoxyalkylene units, the side chains of which are at least partially end-capped with aliphatic alkyl groups, preferably having arms of not more than 4 carbon atoms.

6. 7. The process according to claim 6, characterized in that the polymeric organic compound (P2) in the particulate component (P) of the aqueous dispersion also contains imidazole units.

7. 8. The process according to claim 6, wherein the proportion of polyoxyalkylene units in all said polymeric organic compounds (P2) is at least 40% by weight, preferably at least 50% by weight, but does not exceed 70% by weight.

8. In process step (i) and / or process step (ii), PO ４ 8. The process according to claim 1 , characterized in that the proportion of phosphate contained in the at least one particulate inorganic compound (P1), calculated as ρ / ρ / ρ / ρ, relative to the dispersed inorganic particle component of the aqueous dispersion, is at least 25% by weight, preferably at least 35% by weight, particularly preferably at least 40% by weight and very particularly preferably at least 45% by weight.

9. 9. The process according to claim 1, characterized in that in process step (i) and / or process step (ii), the aqueous dispersion contains as further component at least one thickener, preferably selected from urea-urethane resins, preferably having an amine number of less than 8 mg KOH / g, particularly preferably less than 5 mg KOH / g, very particularly preferably less than 2 mg KOH / g.

10. 10. The process according to any one of claims 1 to 9, characterized in that the water-dispersed particle component (P) of the aqueous dispersion in process step (i) is at least 0.060 g / kg, preferably at least 0.100 g / kg, but preferably not more than 5.0 g / kg, particularly preferably not more than 1.0 g / kg, of the aqueous dispersion.

11. 11. The process according to claim 1, wherein the aqueous dispersion in process step (i) for activating the zinc surface has a pH value of more than 6.0, preferably more than 6.5, but preferably not more than a pH value of 9.0, particularly preferably not more than a pH value of 8.5, very particularly preferably not more than a pH value of 8.0, particularly preferably not more than a pH value of 7.

5.

12. 12. The process according to claim 1, wherein in process step (ii) the aqueous dispersion is added in an amount such that the weight proportion of the phosphate salt of the water-dispersed particle component (D) is at least 0.1 mg / kg, preferably at least 0.5 mg / kg, particularly preferably at least 1.0 mg / kg, very particularly preferably at least 2.0 mg / kg, based on the acidic aqueous composition.

13. 13. The process according to any one of claims 1 to 12, characterized in that the acidic aqueous composition for the zinc phosphate treatment in process step (ii) has a pH value of less than 3.6, preferably less than 3.4, particularly preferably less than 3.2, and the free acidity is preferably more than 0.5 points, particularly preferably more than 0.8 points, particularly preferably more than 1.0 points.

14. 14. Process according to any one of claims 1 to 13, characterized in that the series of components at least partly have zinc surfaces, preferably also iron surfaces, and very particularly preferably also aluminum surfaces.

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