Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
  • C23C22/362—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also zinc cations
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
  • C23C22/364—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also manganese cations
  • C23C22/365—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also manganese cations containing also zinc and nickel cations
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
  • C23C22/76—Applying the liquid by spraying
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
  • C23C22/77—Controlling or regulating of the coating process
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated

Definitions

• the present invention relates to a method for the corrosion-protective pretreatment of a large number of components in series, in which each component in the series has at least partial surfaces made of zinc and/or iron and at least parts of these surfaces are initially specifically activated for subsequent zinc phosphating.
• the targeted activation is achieved by means of controlled dispensing of an aqueous dispersion for wetting the aforementioned surfaces of zinc and/or iron, so that resource-saving activation is ensured (“activation wetting").
• the aqueous dispersion for activation wetting contains a particulate component dispersed in water, which is at least partially composed of hopeite, phosphophyllite, scholzite and/or hureaulite, provided as a dispersion of these crystalline solids, which is stabilized with at least one polymeric, organic compound.
• the phosphating quality of the acidic, aqueous composition of the zinc phosphating is in turn ensured and maintained by adding an amount of an aqueous dispersion, in particular the same aqueous dispersion that is also used for activation wetting.
• Layer-forming phosphating is a process that has been used for decades and intensively researched for applying crystalline anti-corrosive coatings to metallic surfaces, particularly to iron, zinc and aluminium.
• Zinc phosphating which is particularly well-established for corrosion protection, is carried out in a layer thickness of a few micrometres and is based on a corrosive pickling of the metallic material in an acidic aqueous composition containing zinc ions and phosphates, during which poorly soluble crystallites form near the surface, which precipitate directly at the interface with the metallic material and continue to grow there.
• Zinc phosphating is usually adjusted in such a way that homogeneous, closed and compact crystalline coatings are achieved on the material surfaces of the metals iron, zinc and aluminum. Otherwise, good corrosion protection and paint adhesion cannot be achieved. Homogeneous, closed coatings in zinc phosphating are typically reliably achieved from a layer weight of 2 g/m 2 .
• zinc phosphating is usually initiated in the state of the art by activating the metallic surfaces of the component to be phosphated.
• Activation is a wet-chemical process step that is conventionally carried out by bringing into contact with colloidal, aqueous solutions of phosphates ("activation stage"), which, when immobilized on the metal surface, serve as growth nuclei for the formation of the crystalline coating in the subsequent phosphating, so that a high number density of growing crystallites is achieved and in turn a compact crystalline zinc phosphate layer is generated, which offers excellent corrosion protection and, due to Due to its high electrical resistance it also has excellent electrocoatability.
• the task was solved in this case by the selective and controlled release of an aqueous dispersion for the activating wetting of metal surfaces before the actual integrated zinc phosphating.
• the activating wetting of the surfaces of zinc and/or iron surprisingly enables a significant reduction in the layer weight of the zinc phosphating with the same phosphating quality and thus an equally significantly reduced consumption of active components in the zinc phosphating.
• the present invention specifically relates to a method for the corrosion-protective pretreatment of a large number of components in series, in which each component of the series has at least partially surfaces of zinc and/or iron and first undergoes a process step (i) for activating the surfaces of zinc and/or iron and immediately thereafter a process step (ii) for zinc phosphating,
• Pretreatment in series occurs when the individual components of the series are successively and thus separated from one another in time, each undergoing process steps (i) and (ii) for zinc phosphating in accordance with the process according to the invention and are brought into contact with the corresponding aqueous compositions stored in system tanks in the intended immediate sequence.
• the system tank of process step (i) is the container in which the aqueous dispersion is kept in stock for the purpose of activating the surfaces of zinc and/or iron
• the system tank of process step (ii) is accordingly the container that contains the acidic aqueous composition for the purpose of zinc phosphating.
• the components in process step (ii) can be brought into contact with the acidic, aqueous composition inside the system tank, for example by immersion, or outside the system tank, for example by spraying or squirting the acidic aqueous composition stored in the system tank.
• the contacting of the zinc and/or iron surfaces of each component in the series with the aqueous dispersion in process step (i) is carried out by dispensing a defined volume of the dispersion from the supply onto the surfaces to be activated, preferably in such a way that the volume of aqueous dispersion dispensed once per component is not returned to the system tank storing the dispersion, for example by wetting the surfaces to be activated outside the system tank from which the stored aqueous dispersion is dispensed per component.
• the components treated according to the present invention can be any spatial structure of any shape and design that originates from a manufacturing process, in particular also semi-finished products such as strips, sheets, rods, pipes, etc. and composite structures assembled from the aforementioned semi-finished products, wherein the semi-finished products are preferably connected to one another to form the composite structure by gluing, welding and/or flanging.
• the method according to the invention is particularly effective for producing compact, closed and crystalline phosphate coatings on the surfaces of zinc, so that components in the series are those that have at least surfaces of zinc.
• the method according to the invention is also well suited for the layer-forming phosphating of aluminum, so that components in mixed construction, e.g. automobile bodies, assembled from the materials zinc, iron and aluminum can be phosphated effectively and in a resource-saving manner in the sense of the present invention.
• the surfaces of aluminum generally do not require pre-activation in process step (i) and sufficient layer formation occurs when the surfaces of aluminum are brought into contact with the acidic aqueous composition in process step (ii).
• the components of the series which at least partially have surfaces of zinc and/or iron also additionally have surfaces of the metal aluminum, wherein the surfaces of the metal aluminum are preferably not brought into contact with the dispensed aqueous dispersion in process step (i), but are brought into contact with the acidic, aqueous composition in process step (ii).
• a component has at least one surface made of zinc and/or iron if the metallic structure on this surface is composed of more than 50 at.% zinc or iron up to a material penetration depth of at least one micrometer.
• Components comprising surfaces made of zinc are also iron materials provided with metallic coatings, such as electrolytically galvanized or hot-dip galvanized strip steel, which can also be alloyed with iron (ZF), aluminum (ZA) and/or magnesium (ZM).
• step (ii) For resource-saving operation of the anti-corrosive pretreatment based on zinc phosphating in step (ii), the 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 components is maintained to the maximum for the zinc phosphating stage and, on the other hand, the zinc phosphating treatment stage is sharpened with essential, activating particulate phosphates, since these are introduced into the phosphating stage via the wet film adhering to the component.
• the direct sequence of activation and zinc phosphating means that the components undergo the process step (i) without an intermediate rinsing step or other treatment step which either comprises further contacting, in particular of the zinc or iron surfaces of the components, with an aqueous dispersion containing a water-dispersed, particulate constituent (P) in the manner of process step (i) or preferably contacting, in particular of the zinc or iron surfaces of the components, with an aqueous dispersion for activation for zinc phosphating or particularly preferably contacting with an aqueous composition, wherein in each case preferably no drying step is carried out after process step (i) and before process step (ii).
• a rinsing step in this context can comprise one or more immediately consecutive process steps which serve to remove soluble residues, particles and/or active components which inevitably remain on the surfaces of the components after they have been discharged from previous wet-chemical process steps. to remove them as completely as possible, e.g. by rinsing with city water.
• a drying step in the same context is the drying of the components by means of controllable technical measures, e.g. by supplying heat or by directing air supply.
• a further advantage of the compact, closed and crystalline coatings that can be obtained on all these metal surfaces using the method according to the invention is their excellent electrocoatability, which enables a high coverage behavior to be achieved.
• step (ii) is followed by electrocoating, particularly preferably cathodic electrocoating.
• any coating with an organic topcoat system that is customary in the prior art, in particular a powder coating can follow the method, since an excellent paint adhesion base is provided.
• the aqueous dispersion is brought into contact to activate at least the surfaces of zinc and/or iron by dispensing it from a supply.
• the dispensing of the aqueous dispersion from a supply for bringing it into contact requires, in the sense of the present invention, the use of a device for removing a volume of liquid from a supply, for example a container that stores a sufficient amount of the aqueous dispersion for a large number of components, and a device for dispensing the removed volume of liquid onto the surfaces of one or more components that are to be brought into contact.
• the components are therefore not brought into contact in the stored aqueous dispersion, i.e.
• the volume of the aqueous dispersion dispensed from the supply for bringing into contact is limited and should be less than 1.00 liter per square meter of the surface of the component or preferably only the zinc and/or iron surfaces of the component. This ensures that not significantly more liquid volume of the aqueous dispersion is dispensed than would be required for complete wetting of the zinc and/or iron surfaces with a liquid film of the aqueous dispersion.
• the aqueous dispersion is applied to the surfaces to be treated as effectively as possible and without excess quantity.
• the surfaces of zinc and/or iron are brought into contact by dispensing the aqueous dispersion from a supply to such an extent that no more than 0.50 liter, preferably no more than 0.20 liter of the aqueous dispersion is dispensed per square meter of the surfaces of the component, preferably only the zinc and/or iron surfaces of the component to be activated and thus brought into contact.
• the area-related volume output of the aqueous dispersion is such that the area of a component in the series represents the surface of the polyhedron with 12 surfaces, preferably with 6 surfaces, and is particularly preferably the cuboid that completely surrounds the component and has the smallest surface area, with each surface of the polyhedron touching the component at at least one point.
• the component is an automobile body
• its area in connection with the area-related output of the aqueous dispersion for conditioning is preferably that of the cuboid with the smallest surface area that completely surrounds the automobile body, with each surface of the cuboid touching the automobile body at at least one point.
• the respective upper limit of the area-related volume output of the aqueous dispersion is standardized to the surfaces of zinc and/or iron.
• the geometric area of the surfaces of the component made of zinc and/or iron to be activated is then taken into account.
• the dispensing of the aqueous dispersion for bringing into contact and thus activating the surfaces of zinc and/or iron requires and requires that the amount dispensed from the supply also reaches these surfaces at least partially.
• the dispensing of the aqueous dispersion for bringing into contact in process step (i) for sufficient activation is therefore carried out in such a way that it is ensured that at least the surfaces of zinc and/or iron are covered by a liquid film containing the aqueous dispersion, resulting in a volume-related coating per square meter of preferably no more than 1.00 liter, particularly preferably no more than 0.50 liter, very particularly preferably no more than 0.20 liter and especially preferably no more than 0.10 liter on the surfaces of zinc and/or iron.
• the volume application does not refer to the surface of the component approximated by polyhedra, but to the respective actual geometric surface of the surfaces of zinc and/or iron of the components of the series, whereby the volume application can be determined by differential weighing after blowing off the liquid film, assuming a density of the liquid adhering to the surfaces of 1 g/cm 3 .
• the components are often already wetted with a liquid film, for example formed by rinsing water from a rinsing step immediately preceding the activation, when they are transferred to the activation stage according to process step (i), before the inventive bringing into contact of the surfaces of zinc and/or iron is then carried out by Absorption of liquid volume of the aqueous dispersion in the wet film already adhering to these surfaces takes place.
• a process variant can be particularly advantageous because the active components absorbed by the wet film adhering to the component are better absorbed by the pre-wetted surfaces of the component and then distributed more homogeneously over them, which in turn promotes uniform activation for the subsequent zinc phosphating.
• the device for dispensing and bringing into contact alone is sufficient to achieve a largely complete wetting of the zinc and/or iron surfaces to be activated, it may again be advantageous for reasons of efficiency to remove the wet film adhering to the components from previous treatment steps immediately before process step (i) or immediately before the zone in which the aqueous dispersion is dispensed for bringing into contact, for example by blowing or wiping, in order to use as efficiently as possible only those aqueous dispersions whose particulate content is relatively low but still just sufficient to bring about the desired activation.
• Whether a liquid film containing the aqueous dispersion is formed on the surfaces of zinc and/or iron in process step (i) can be checked using fluorescent markers that are added to the supply of the aqueous dispersion.
• the detection can then be carried out by irradiating with UV light and recording the fluorescence using suitable cameras that enable imaging control of the wetting of the component surfaces with the aqueous dispersion. This is particularly helpful when components with complex surface geometries have to be pretreated and the type of output of the aqueous dispersion, e.g.
• the relative orientation and spacing of a spray lance to the component has to be adjusted in an iterative process in such a way that the surfaces of zinc and/or iron are brought into contact with the aqueous dispersion, in particular in such a way that these surfaces are covered with a liquid film containing the aqueous dispersion.
• the latter preferred condition does not have to be fulfilled immediately by bringing the aqueous dispersion from the supply into contact, i.e. directly by the application device, but it is sufficient if, for example by rotating, pivoting or tilting the components, a liquid film containing the aqueous dispersion in contact with the surfaces of zinc and/or iron is produced before process step (ii), i.e. before the components are introduced into the zinc phosphating, preferably at least 5 seconds, particularly preferably at least 10 seconds, very particularly preferably at least 20 seconds, before bringing them into contact with the acidic aqueous composition in process step (ii).
• the release of the aqueous dispersion is as a spray, as a spray mist or as a liquid film, particularly preferably as a spray and/or aerosol, particularly preferably as a spray.
• the aqueous dispersion is brought into contact with the surfaces of the component to be activated as a spray and/or aerosol using methods for spraying and misting that are established in the state of the art and can be done locally using a spray lance and/or at least partially enclosing the component using a spray ring in which a large number of atomizer nozzles can be installed.
• the spray devices used to emit a spray and/or aerosol are, for example, pressure atomizers, rotary atomizers or two-substance atomizers.
• a liquid film can be applied to the component using rollers, cloths, brushes, paintbrushes or similar tools for applying liquids in a direct application process.
• a preferred controlled and efficient activation wetting with the aqueous dispersion is achieved by setting a spray rain that is specifically directed at the surfaces of zinc and/or iron to be wetted and/or by providing a spray mist through which the component is transported together with the conveyor frame and which, at a given volume flow, is realized over such a transport path that the surfaces of the component to be wetted are preferably exposed to a closed liquid film containing the aqueous dispersion before the component is brought into contact with the acidic aqueous composition for zinc phosphating in the immediately following process step (ii).
• the dispersion dispensed as a spray and/or as a spray mist in process step (i) has an average droplet size of less than 100 ⁇ m, particularly preferably less than 60 ⁇ m, especially preferably less than 40 ⁇ m. With average droplet sizes below 40 ⁇ m, the aqueous dispersion is so highly atomized that the boundary area to the aerosols is exceeded and a spray mist is formed.
• the aqueous dispersion dispensed in process step (i) has an average droplet size of not less than 5 ⁇ m, particularly preferably not less than 10 ⁇ m.
• a closed liquid film containing the aqueous dispersion on the surfaces of the components is also advantageous for the formation of a closed liquid film containing the aqueous dispersion on the surfaces of the components to be brought into contact if the Spray and/or mist of the aqueous dispersion is dispensed such that the average speed of the liquid droplets having the average droplet size is less than 5 m/s, preferably less than 2 m/s and particularly preferably less than 1 m/s.
• sprays and/or mist whose average droplet size is less than 100 ⁇ m, particularly preferably less than 60 ⁇ m, especially preferably less than 40 ⁇ m.
• the average droplet size and average speed of the droplets of a spray or mist are determined at the location of the geometric center of gravity of the polyhedron surrounding the component, which is also used to determine the amount of agent dispensed per area of the component as described above.
• the determination can be made using light scattering and phase Doppler anemometry.
• the preferred embodiments mentioned here for how the aqueous dispersion can be dispensed for contact with at least the surfaces of zinc and/or iron make it possible to carry out an extremely efficient process in which the amount of aqueous dispersion dispensed from the supply is essentially only applied to the surfaces of zinc and/or iron of the components that are to be activated.
• the portion of the aqueous dispersion that is carried along with the component into the zinc phosphating treatment stage serves to at least partially compensate for the particulate portion of the acidic aqueous composition for zinc phosphating that is consumed during the activated zinc phosphating and carried out from the zinc phosphating treatment stage.
• the portion of the components of the aqueous dispersion that are released but do not remain on the component can be combined and transferred to the zinc phosphating treatment stage to maintain the activation performance.
• a method is preferred according to the invention in which the portions of the aqueous dispersion which are dispensed in process step (i) for bringing into contact with at least the surfaces of zinc and/or iron of the components, but which do not remain on the component as a wet film until they are brought into contact with the acidic aqueous composition for zinc phosphating in process step (ii), because they sink to the bottom as excess spray or run off the component and thus remain in the spray chamber of process step (i), are at least partially combined and added to the acidic aqueous composition of process step (ii), and in any case preferably are neither partially nor completely returned to the supply.
• the aqueous dispersion used contains a water-dispersed, particulate component (P) composed of phosphates of polyvalent metal cations (P1) and a polymeric organic compound (P2) contributing to the stabilization of the dispersion.
• P water-dispersed, particulate component
• P1 phosphates of polyvalent metal cations
• P2 polymeric organic compound
• the preferred proportion of phosphates calculated as PO 4 contained in the at least one particulate inorganic compound (P1) based on the dispersed, inorganic particulate component (P1) of the aqueous dispersion is at least 25% by weight, particularly preferably at least 35% by weight, especially preferably at least 40% by weight, very particularly preferably at least 45% by weight.
• Further preferred embodiments of the inorganic particulate component (P1) can, as already explained, be taken from the corresponding preferred embodiments for the inorganic particulate component (P1) of the aqueous dispersion of process step (ii).
• the polymeric organic compound (P2) in the particulate component (P) of the aqueous dispersion is composed at least in part of styrene and/or an ⁇ -olefin having no more than 5 carbon atoms for excellent dispersion stability, the polymeric organic compound (P2) additionally having units of maleic acid, its anhydride and/or its imide and preferably additionally polyoxyalkylene units, particularly preferably polyoxyalkylene units, in its side chains, which in turn are preferably at least partially end-capped with aliphatic alkyl groups having no more than four carbon atoms.
• the polymeric organic compound (P2) in the particulate component (P) of the aqueous dispersion additionally also has imidazole units.
• the proportion of polyoxyalkylene units in the totality of the polymeric organic compounds (P2) is preferably at least 40% by weight, particularly preferably at least 50% by weight, but is preferably not above 70% by weight. Further preferred embodiments of the polymeric organic compound (P2) can, as already explained, be taken from the corresponding preferred embodiments for the polymeric organic compound (P2) of the aqueous dispersion of process step (ii).
• the presence of a thickener is advantageous for providing a stable dispersion that can be stored in the system tank of process step (i) over a longer period of time.
• the aqueous dispersion in process step (i) therefore contains at least one thickener as a further component, which is preferably selected from urea urethane resins, particularly preferably from urea urethane resins that have an amine number of less than 8 mg KOH/g, preferably less than 5 mg KOH/g, particularly preferably less than 2 mg KOH/g.
• thickener is described in connection with the aqueous dispersion additized in process step (ii) of the zinc phosphating, which are also advantageous with regard to the aqueous dispersions used in the preactivation and are also included here as preferred.
• aqueous dispersion containing the water-dispersed, particulate constituent (P) used in step (i) according to the invention can be found in the description of particularly suitable activating aids.
• the extent of the pre-activation of the surfaces of zinc and/or iron can be controlled via the particulate portion of the aqueous dispersion dispersed in water. It has been found that the surfaces of zinc and/or iron are pre-activated particularly reliably at typical activation times, i.e. a contact duration in the range of 5 to 120 seconds, when the particulate portion (P) is at least 0.060 g/kg based on the aqueous dispersion.
• Short activation times can be compensated with higher proportions of the particulate portion (P), so that overall it is advantageous if the water-dispersed, particulate component (P) of the aqueous dispersion in process step (i) is at least 0.060 g/kg, particularly preferably at least 0.100 g/kg.
• Significantly higher contents are associated with higher economic expenditure, which is not compensated by a significant improvement in the compactness of the zinc phosphate coatings then achieved, and are also often not required for sharpening the proportion of particulate components in the acidic, aqueous composition of the zinc phosphating by carryover, thus counteracting the intention of the present invention to establish a particularly resource-saving process for zinc phosphating.
• the water-dispersed, particulate component (P) of the aqueous dispersion in process step (i) is not more than 5.0 g/kg, particularly preferably not more than 1.0 g/kg, based on the aqueous dispersion.
• the pH value of the aqueous dispersion for the pre-activation is preferably set so that the metallic materials of the components, in particular the components made of zinc, iron or aluminum, are not pickled. Accordingly, it is preferred if the aqueous dispersion in process step (i) for activating the zinc surfaces has a pH value above 6.0, particularly preferably above 6.5, but preferably a pH value of 9.0, particularly preferably 8.5, very particularly preferably 8.0 and especially preferably 7.5 is not exceeded.
• the acidic, aqueous zinc phosphating is thus provided in an activating manner for the growth of a crystalline phosphate coating on the surfaces of zinc and/or iron due to its particulate component (D) and is obtainable as such by appropriate addition of an amount of an aqueous dispersion to an acidic, aqueous composition containing the aforementioned components (A) - (C).
• such an amount of the activating aid is dispensed per component for bringing into contact with the surfaces of zinc and/or iron that is sufficient to maintain, as a wet film remaining on the component and introduced into the subsequent process step (ii) of zinc phosphating, in the acidic, aqueous composition containing the components (A) - (C), a weight proportion of the phosphates of the water-dispersed, particulate component (D) comprising phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and/or hureaulite of at least 0.1 mg/kg, particularly preferably at least 0.5 mg/kg, very particularly preferably at least 1.0 mg/kg and especially preferably at least 2.0 mg/kg, each calculated as phosphate (PO 4 ) and based on the acidic aqueous composition.
• such an amount of the activating aid is dispensed per component for bringing into contact with the surfaces of zinc and/or iron, which is sufficient as a wet film remaining on the component and introduced into the subsequent process step (ii) of zinc phosphating to set in the acidic, aqueous composition containing the components (A) - (C) such a minimum amount of the water-dispersed, particulate component (D) comprising phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and/or hureaulite, which is sufficient to ensure, under the selected conditions of process step (ii) of zinc phosphating, the property of the acidic aqueous composition to form a zinc phosphate layer with a layer weight of less than 4.5 g/m 2 , preferably less than 4.0 g/m 2 , particularly preferably less than 3.5 g/m 2 , most
• the (Z) substrates are considered to have been cleaned and degreased if the (Z) surface has a carbon coating of less than 0.10 g of carbon per square meter of the (Z) surface after cleaning and degreasing.
• the carbon coating can be determined by means of pyrolytic decomposition.
• the (Z) substrate is brought to a substrate temperature of 550°C (PMT) in an oxygen atmosphere and the amount of carbon dioxide released is quantitatively recorded as the amount of carbon using an infrared sensor, for example using the LECO ® RC-412 Multiphase Carbon Determinator (Leco Corp.) analysis device.
• hot-dip galvanized steel (Z) is first cleaned with an alkaline cleaner as 2 wt.% Bonderite ® C-AK 1565 A and 0.2 wt.% Bonderite ® C-AD 1270 in deionized water ( ⁇ 1 ⁇ Scm -1 ) at pH 11.0 and 55 °C for 5 minutes by immersion.
• the substrates (Z) cleaned and degreased in this way are rinsed with deionized water ( ⁇ 1 ⁇ Scm -1 ) at room temperature and then fed to the treatment stages according to process steps (i) and (ii) in accordance with the process conditions selected in each case.
• the resulting target layer weights on hot-dip galvanized steel (Z) should be below 4.5 g/m 2 , preferably below 4.0 g/m 2 , particularly preferably below 3.5 g/m 2 and very particularly preferably below 3.0 g/m 2 .
• the phosphating quality can therefore be determined in the ongoing process according to the invention by introducing cleaned and degreased sheets of hot-dip galvanized steel (Z) for process steps (i) and (ii) along with the components of the series, and then determining the layer weight of zinc phosphate on the sheets and thus the phosphating quality of the acidic aqueous composition for zinc phosphating in process step (ii).
• the outer surfaces of such test sheets to be phosphated in process step (i) have a a complete liquid film containing the aqueous dispersion has been formed before contact with the acidic aqueous composition in process step (ii).
• the cleaned and degreased sheets of hot-dip galvanized steel (Z) are rigidly connected to the component or the conveyor frame in their function as test sheets for determining the phosphating quality in order to reproduce the flow conditions when transporting the component together with the conveyor frame through the phosphating bath as closely as possible for the test sheet.
• the test sheets should ideally be connected to the component or the conveyor frame in such a way that the transport of a test sheet together with the component and the conveyor frame has no significant influence on the flow conditions compared to the transport of the component and the conveyor frame without such a test sheet and that the flow conditions in both cases are essentially identical and thus essentially correspond to the flow conditions of at least a portion of the components in the series.
• test sheet size and/or shape of the test sheet to the size and shape of the component and/or the conveyor frame, which is arranged adjacent to the test sheet. It is conceivable, particularly when a test sheet is arranged on an external surface section of the component or the conveyor frame, to dimension the test component accordingly smaller than said surface section, for example in order to avoid the test component protruding beyond the surface section. Alternatively or additionally, the test component can follow a curvature or another plane deviation of the surface section or the conveyor frame.
• the spacing of the sample sheet is carried out along a surface normal to a surface of zinc and/or iron of the component in order to ensure in the simplest possible way that in process step (i) a liquid film containing the aqueous dispersion dispensed there for bringing into contact is applied without the device for dispensing the aqueous dispersion in process step (i) having to be adapted with effort.
• the phosphating quality is obtained directly from the series treatment of such components which, as surfaces of zinc, also have a surface of hot-dip galvanized steel (Z).
• Such components are also preferred in a preferred embodiment of the method according to the invention.
• the coating weight on hot-dip galvanized steel (Z) should not be increased by more than 0.2 g/m 2 and thus the layer formation under the selected conditions is already in the range of self-limitation, so that the property of the acidic aqueous composition for zinc phosphating to produce compact, crystalline zinc phosphate layers in step (ii) of the process according to the invention is ensured.
• such an amount of the aqueous dispersion containing the particulate constituent (P) is added that is sufficient under the selected conditions of the zinc phosphating process step in the process according to the invention to maintain the property of the acidic aqueous composition of depositing a zinc phosphate layer with a layer weight of less than 4.5 g/m 2 , preferably less than 4.0 g/m 2 , particularly preferably less than 3.5 g/m 2 and very particularly preferably less than 3.0 g/m 2 on a hot-dip galvanized steel surface (Z), wherein the layer weight achieved under the selected conditions of the zinc phosphating process step (ii) in the process according to the invention does not increase by more than 0.2 g/m 2 when the contact time with the acidic, aqueous composition is extended by 60 seconds.
• the phosphating quality is determined and monitored by regularly subjecting hot-dip galvanized steel (Z) that has been cleaned and degreased as described above to the zinc phosphating process step during the series treatment and then subjecting it to a layer weight determination.
• the phosphating quality is determined directly during the series treatment of components that have at least one surface of hot-dip galvanized steel (Z) as zinc surfaces.
• the zinc phosphate layer weight is determined in the context of the present invention by removing the zinc phosphate layer with an aqueous 5 wt.% CrOs pickling solution, which is brought into contact with a defined area of the phosphated material or component immediately after zinc phosphating and rinsing with deionized water ( ⁇ 1 ⁇ Scm -1 ) at 25 °C for 5 minutes and then determining the phosphorus content in the same pickling solution using ICP-OES.
• the zinc phosphate layer weight is obtained by multiplying the area-related amount of phosphorus in grams per square meter by a factor of 6.23.
• the addition of the aqueous dispersion containing the particulate component (P) to the acidic aqueous composition for zinc phosphating is carried out in the process according to the invention for the purpose of maintaining the phosphating quality in process step (ii).
• the addition can be carried out for the purpose of maintaining the phosphating quality in the process of series treatment by continuous or discontinuous dosing into the system tank of the zinc phosphating Continuous dosing is preferred when the pretreatment of the components in series follows one another immediately and the decrease in the phosphating quality per time interval can be determined with sufficient accuracy, so that a continuous dosing of an amount of the activating agent can be carried out to compensate for the loss in performance.
• This process has the advantage that the phosphating quality does not have to be monitored further after the pretreatment line has been started up and the material flows for the dosing of the aqueous dispersion and other active components have been determined, as long as the series treatment with regard to timing and nature of the components to be treated and the treatment parameters in process step (ii) of zinc phosphating remain unchanged.
• a discontinuous dosing of the aqueous dispersion containing the particulate component (P) is advantageous and may even be indicated.
• the phosphating quality of the acidic aqueous composition in step (ii) is preferably monitored continuously or at defined time intervals and then a predetermined amount of the activating aid is added when the layer weight on hot-dip galvanized steel (Z) no longer reaches a certain value below 4.5 g/m 2 , preferably below 4.0 g/m 2 , particularly preferably below 3.5 g/m 2 and very particularly preferably below 3.0 g/m 2 .
• the continuous or quasi-continuous determination of the phosphating quality at defined time intervals can also be carried out using proxy data that correlate with the actual zinc phosphate layer weight.
• the non-destructive determination of the layer thickness using the eddy current method or even contact-free optical determination methods such as ellipsometry or spectral reflectivity measurement provides suitable proxy data for the layer weight of zinc phosphate, which can be reliably measured in a pretreatment line on the zinc surfaces of the components and correlated with the actual layer weight on hot-dip galvanized steel (Z).
• the crystallite size and thus the determination of the roughness using optical profilometry can also provide proxy data for the layer weight, since a higher layer weight on hot-dip galvanized steel (Z) is associated with a low number density of crystallites, which are however relatively larger, so that the roughness increases with the layer weight.
• the phosphating quality is already sufficiently adjusted in most cases if the aqueous dispersion containing the particulate component (P) for activating the zinc phosphating composition is continuously or discontinuously added in an amount that is suitable for maintaining a stationary amount of preferably at least 0.1 mg/kg, particularly preferably at least 0.5 mg/kg, especially preferably at least 1.0 mg/kg of phosphates contained in the water-dispersed, particulate component (D) in the acidic aqueous composition, each calculated as the amount of phosphate (PO 4 ) and based on the acidic aqueous composition during the pretreatment of the components in series.
• the activated zinc phosphating in step (ii) can be carried out in a particularly resource-efficient manner and the consumption of active components can be significantly reduced without any loss of phosphating quality. This applies to the added portion of the aqueous dispersion containing the particulate component (P) and, due to the excellent phosphating quality achieved on the surfaces of zinc and/or iron, also to the consumption of active components (A) - (C) of the acidic aqueous composition for zinc phosphating.
• the amount of phosphate ions includes the orthophosphoric acid as well as the anions of the salts of orthophosphoric acid dissolved in water, calculated as PO 4 .
• the proportion of free acid in points in the acidic aqueous composition of the zinc phosphating 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 more than 3.0, particularly preferably not more than 2.0.
• the proportion of free acid in points is determined by diluting 10 ml sample volume of the acidic, aqueous composition to 60 ml and titrating with 0.1 N sodium hydroxide solution to a pH of 3.6. The consumption of ml of sodium hydroxide solution indicates the number of points of free acid.
• the preferred pH of the acidic, aqueous composition is usually below 3.6, particularly preferably below 3.4, very particularly preferably below 3.2, but preferably above 2.5, particularly preferably above 2.7.
• the "pH" as used in the context of the present invention corresponds to the negative decimal logarithm of the hydronium ion activity at 20 °C and can be determined using pH-sensitive glass electrodes.
• a quantity of free fluoride or a source of free fluoride ions is essential for the process of layer-forming zinc phosphating.
• components are to be zinc phosphated to form a layer, in addition to zinc surfaces, also iron or aluminum surfaces,
• the amount of free fluoride in the acidic aqueous composition in step (ii) is at least 10 mg/kg, particularly preferably at least 40 mg/kg.
• the concentration of free fluoride should not exceed values above which the phosphate coatings have loose adhesions which are easily wiped off.
• step (ii) of the process according to the invention the concentration of free fluoride in the acidic aqueous composition of the zinc phosphating is below 300 mg/kg, particularly preferably below 250 mg/kg and especially preferably below 200 mg/kg.
• the amount of free fluoride is to be determined potentiometrically at 20 °C in the respective acidic, aqueous composition after calibration with fluoride-containing buffer solutions without pH buffering using a fluoride-sensitive measuring electrode.
• Suitable sources of free fluoride ions are hydrofluoric acid and its water-soluble salts, such as ammonium bifluoride and sodium fluoride, as well as complex fluorides of the elements Zr, Ti and/or Si, in particular complex fluorides of the element Si.
• the source of free fluoride in a phosphating according to the present invention is therefore selected from hydrofluoric acid and its water-soluble salts and/or complex fluorides of the elements Zr, Ti and/or Si.
• Salts of hydrofluoric acid are water-soluble in the sense of the present invention if their solubility in deionized water ( ⁇ ⁇ 1 ⁇ Scm -1 ) at 60 °C is at least 1 g/L calculated as F.
• the source of free fluoride in step (ii) is at least partially selected from complex fluorides of the element Si, in particular from hexafluorosilicic acid and its salts.
• speck formation is the phenomenon of the local deposition of amorphous, white zinc phosphate in an otherwise crystalline phosphate layer on the treated zinc surfaces or on the treated galvanized or alloy-galvanized steel surfaces.
• the accelerators known in the prior art can be added to the acidic, aqueous composition to increase the layer formation rate.
• These are preferably selected from 2-hydroxymethyl-2-nitro-1,3-propanediol, nitroguanidine, N-methylmorpholine-N-oxide, nitrite, hydroxylamine and/or hydrogen peroxide.
• aqueous dispersion containing the water-dispersed, particulate component (P) is necessary to provide the acidic, aqueous composition or a smaller stationary amount of the water-dispersed, particulate component (P) must be maintained in the acidic, aqueous composition for zinc phosphating in step (ii) if nitroguanidine or hydroxylamine is used as an accelerator, so that nitroguanidine or hydroxylamine, in particular nitroguanidine are particularly preferred as accelerators in the acidic aqueous composition in step (ii) of the process according to the invention in view of a particularly low material usage for maintaining the phosphating quality.
• an embodiment in which a total of less than 10 ppm of nickel and/or cobalt ions are contained in the acidic aqueous composition for zinc phosphating in step (ii) of the process according to the invention is particularly preferred.
• process according to the invention can also make use of the additivation which is well known in the art in zinc phosphating processes.
• Preferred embodiments of the aqueous dispersion containing the water-dispersed, particulate constituent (P) used in step (ii) according to the invention can be found in the description of particularly suitable activating aids.
• dispersed particulate component (P) of the aqueous dispersion and the at least one particulate inorganic compound (P1) or polymeric organic compound (P2) regardless of whether the dispersed particulate component (P) is a component of the aqueous dispersion for pre-activation in process step (i) or a component of the aqueous dispersion for providing the self-activating, acidic aqueous composition for zinc phosphating in process step (ii).
• activation aid instead of the respective "aqueous dispersions containing a dispersed component (P)".
• the preferred activating aids are characterized in that they have a high stability against agglomeration, thus being particularly suitable for the formation of crystalline phosphate coatings and, in particular when used according to the invention, releasing a high proportion of phosphate particles with an activating effect or providing them for the activation of the surfaces of zinc and/or iron, so that compact, closed, crystalline coatings with a relatively low layer weight can be achieved particularly reliably in the process according to the invention.
• Activation aids which are used according to the invention, i.e. both for pre-activation in step (i) and for maintaining the phosphating quality or for providing the acidic, aqueous composition for zinc phosphating in step (ii), are thus aqueous dispersions containing a particulate component (P) dispersed in water, which contains at least one particulate inorganic compound (P1) which consists of phosphates of polyvalent metal cations at least partially selected from hopeite, phosphophyllite, scholzite and/or Hureaulite and at least one polymeric organic compound (P2).
• the proportion of phosphates contained in the particulate inorganic compounds (P1) based on the dispersed, inorganic component of the activating aid is preferably at least 25% by weight, particularly preferably at least 35% by weight, especially preferably at least 40% by weight, very particularly preferably at least 45% by weight.
• the dispersed particulate component (P) of the activating agent - or the water-dispersed particulate component (D) of the acidic aqueous composition in step (ii) - is the solids content that remains after drying the retentate of an ultrafiltration of a defined partial volume of the activating agent - or of the acidic aqueous composition - with a nominal exclusion limit of 10 kD (NMWC, Nominal Molecular Weight Cut Off).
• the ultrafiltration is carried out with the addition of deionized water ( ⁇ ⁇ 1 ⁇ Scm -1 ) until a conductivity of less than 10 ⁇ Scm -1 is measured in the filtrate.
• the inorganic particulate component of the activating agent - or the inorganic, water-dispersed, particulate component of the acidic aqueous composition in step (ii) - is in turn the one that remains when the particulate component (P) or (D) obtained from the drying of the retentate of the ultrafiltration is pyrolyzed in a reaction furnace with the addition of a CO 2 -free oxygen stream at 900 °C without the addition of catalysts or other additives until an infrared sensor in the outlet of the reaction furnace delivers a signal identical to the CO 2 -free carrier gas (blank value).
• the phosphates contained in the respective inorganic particulate component, calculated as PO 4, are determined after acid digestion of the same with an aqueous 10 wt.% HNO s solution at 25 °C for 15 min by means of atomic emission spectrometry (ICP-OES) directly from the acid digestion as the phosphorus content multiplied by the factor 3.07.
• ICP-OES atomic emission spectrometry
• the active components of the activation aid are primarily composed of phosphates, which in turn are at least partially selected from hopeite, phosphophyllite, scholzite and/or hureaulite, 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 surfaces of zinc and/or iron in the process according to the invention is based essentially on the phosphates in particulate form contained in the activation aid.
• Hopeites stoichiometrically comprise Zn 3 (PO 4 ) 2 and the nickel and manganese-containing variants Zn 2 Mn(PO 4 ) 3 , Zn 2 Ni(PO 4 ) 3 without taking crystal water into account, whereas phosphophyllite consists of Zn 2 Fe(PO 4 ) 3 , scholzite from Zn 2 Ca(PO 4 ) 3 and hureaulite from Mn 3 (PO 4 ) 2 .
• XRD X-ray diffraction methods
• the activating aid contains at least 20% by weight, particularly preferably at least 30% by weight, especially preferably at least 40% by weight of zinc in the inorganic particulate component based on the phosphate content of the inorganic particulate component, calculated as PO 4 .
• the activating aid should preferably not contain any additional titanium phosphates, since these can also have an activating effect as such, but in the context of the present invention do not have a further positive effect on the phosphating quality.
• the proportion of titanium in the inorganic particulate component of the activating aid is therefore less than 0.01% by weight, particularly preferably less than 0.001% by weight, based on the activating aid.
• the activating aid contains a total of less than 10 mg/kg, particularly preferably less than 1 mg/kg of titanium.
• the polymeric organic compound (P2) that stabilizes the particulate component (P) of the respective dispersion has a major influence on the effectiveness of the activating agent. It turns out that the selection of the polymeric organic compound is crucial for the extent of the pre-activation of the surfaces of zinc and/or iron in process step (i) and the phosphating quality ultimately achieved via the integrated activation in step (ii).
• an organic compound is polymeric 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 respective reference size, which is determined experimentally using size exclusion chromatography with a concentration-dependent refractive index detector at 30 °C and calibrated against polyethylene glycol standards.
• the evaluation of the molar mass averages is carried out computer-aided using the strip method with a 3rd order calibration curve.
• Hydroxylated polymethacrylate is suitable as the column material and an aqueous solution of 0.2 mol/L sodium chloride, 0.02 mol/L sodium hydroxide, 6.5 mmol/L ammonium hydroxide is suitable as the eluent.
• a particularly efficient activating aid which is preferably used in processes according to the invention is present when the polymeric organic compound (P2) used to disperse the particulate inorganic compound (P1) is at least partly composed of styrene and/or an ⁇ -olefin having not more than 5 carbon atoms, wherein the polymeric organic compound (P2) additionally has units of maleic acid, its anhydride and/or its imide and preferably additionally polyoxyalkylene units, particularly preferably polyoxyalkylene units in its side chains.
• the ⁇ -olefin is preferably selected from ethene, 1-propene, 1-butene, isobutylene, 1-pentene, 2-methyl-but-1-ene and/or 3-methyl-but-1-ene and particularly preferably selected from isobutylene. It is clear to the person skilled in the art that the polymeric organic compounds (P2) contain these monomers as structural units in unsaturated form, covalently linked to one another or to other structural units.
• Preferred activating aids include those polymeric organic compounds (P2) which are at least partly composed of styrene.
• the polymeric organic compounds (P2) used for the colloidal stabilization of the particulate constituent (P) of the activating aid preferably have polyoxyalkylene units, which in turn are preferably composed of 1,2-ethanediol and/or 1,2-propanediol, particularly preferably both 1,2-ethanediol and 1,2-propanediol, the proportion of 1,2-propanediols in the total of the polyoxyalkylene units preferably being at least 15% by weight, but particularly preferably not exceeding 40% by weight based on the total of the polyoxyalkylene units.
• the polyoxyalkylene units are preferably contained in the side chains of the polymeric organic compounds (P2).
• a proportion of polyoxyalkylene units in the totality of the polymeric organic compounds (P2) of preferably at least 40% by weight, particularly preferably at least 50% by weight, but preferably not more than 70% by weight is advantageous for their dispersibility.
• the organic polymeric compounds (P2) For anchoring the polymeric organic compound (P2) with the inorganic particulate component (P1) of the activating aid, which is at least partially formed by polyvalent metal cations in the form of phosphates selected from hopeite, phosphophyllite, scholzite and/or hurealite, and an increased stability and ability of the particulate component (P) to activate the surfaces of zinc and/or iron, the organic polymeric compounds (P2) additionally also have imidazole units, particularly preferably in the side chains of the polymeric compounds (P2).
• the amine number of the organic polymeric compounds (P2) is at least 25 mg KOH/g, particularly preferably at least 40 mg KOH/g, however, preferably less than 125 mg KOH/g, particularly preferably less than 80 mg KOH/g, so that in a preferred embodiment the totality of the polymeric organic compounds in the particulate constituent (P) of the activating aid also has these preferred amine numbers.
• the amine number is determined in each case based on a weight of approximately 1 g of the respective reference quantity - organic polymeric compounds (P2) or totality of the polymeric organic compounds in the particulate constituent (P) in 100 ml of ethanol, titrating with 0.1 N HCl standard solution against the indicator bromophenol blue until the color changes to yellow at an ethanolic solution temperature of 20 °C.
• the amount of standard HCl solution used in milliliters multiplied by the factor 5.61 divided by the exact mass of the weight in grams corresponds to the amine number in milligrams KOH per gram of the respective reference quantity.
• the polymeric organic compounds (P2) preferably also the entirety of the polymeric organic compounds in the particulate component (P) have an acid number according to DGF C-V 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, in order to ensure a sufficient number of polyoxyalkylene units.
• the polymeric organic compounds (P2) preferably also the entirety of the 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, especially preferably less than 10 mg KOH/g, in each case determined according to method Ader 01/2008:20503 from European Pharmacopoeia 9.0.
• Suitable commercially available representatives of polymeric organic compounds 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 (Münzing Chemie GmbH), a maleic acid-styrene copolymer modified with EO/PO and imidazole units.
• the proportion of the polymeric organic compounds (P2) preferably the totality of the polymeric organic compounds in the particulate constituent (P), based on the particulate constituent (P), is at least 3 wt. %, particularly preferably at least 6 wt. %, but preferably does not exceed 15 wt. %.
• the activating agent preferably contains no more than 40% by weight of particulate component (P) based on the agent, since otherwise the stability of the dispersion and the process-technical manageability in process steps (i) for pre-activation by wetting by means of spray devices and in process step (ii) for metering the agent into the acidic, aqueous composition of the zinc phosphating by means of metering pumps can no longer be guaranteed or at least is complex.
• activating aids which preferably contain at least 5% by weight, but particularly preferably not more than 30% by weight of particulate constituent (P) based on the agent.
• the activating aid of process step (i), which is used as an aqueous dispersion for wetting the surfaces of zinc and/or iron, on the other hand, is preferably to be concentrated less for wetting by misting and preferably contains not more than 5% by weight of particulate constituent (P) based on the agent, but for good activation preferably at least 0.005% by weight of the particulate constituent (P) based on the agent.
• the agent can additionally be characterized by its D50 value of more than 10 ⁇ m, which is accordingly preferred.
• the aqueous dispersion of the particulate constituents (P) has a D90 value of less than 150 ⁇ m, preferably less than 100 ⁇ m, in particular less than 80 ⁇ m.
• the D50 value or the D90 value refers to the particle diameter that does not exceed 50% by volume or 90% by volume of the particulate constituents contained in the aqueous dispersion.
• the particle size distribution is measured within 120 seconds after the activation aid is added to the dilution volume.
• the presence of a thickener can be advantageous for preventing the irreversible agglomeration of primary particles of the particulate component (P), in particular when the activating agent, as described above, contains at least 5% by weight of particulate component (P) based on the agent.
• the activating agent preferably contains a thickener, again preferably in an amount which gives the activating agent in the shear rate range of 0.001 to 0.25 reciprocal seconds a maximum dynamic viscosity at a temperature of 25 °C of at least 1000 Pa s, but preferably below 5000 Pa s, and preferably results in shear-thinning behavior at shear rates above that which occurs at the maximum dynamic viscosity at 25 °C, i.e.
• the viscosity over the specified shear rate range can be determined using a plate/cone viscometer with a cone diameter of 35 mm and a gap width of 0.047 mm.
• the mixture with water is to be prepared in such a way that the corresponding amount of the polymeric chemical compound is added to the water phase while stirring at 25 °C and the homogenized mixture is then freed of air bubbles in an ultrasonic bath and left to stand for 24 hours.
• the measured viscosity value is then read immediately within 5 seconds after a shear rate of 60 rpm has been applied using spindle number 2.
• the activating agent preferably contains a total of at least 0.5% by weight, but preferably not more than 4% by weight, particularly preferably not more than 3% by weight of one or more thickeners, with the total proportion of polymeric organic compounds in the non-particulate component of the activating agent preferably not exceeding 4% by weight (based on the agent).
• the non-particulate component is the solids content of the respective aqueous dispersion or of the activating agent in the permeate of the ultrafiltration described above after it has been dried to constant mass at 105°C - i.e. the solids content after the particulate component has been separated off by ultrafiltration.
• the thickener is preferably selected from polymeric organic compounds, which in turn are preferably selected from polysaccharides, cellulose derivatives, aminoplasts, polyvinyl alcohols, polyvinylpyrrolidones, polyurethanes and/or urea urethane resins, and particularly preferably from urea urethane resins, in particular those urea urethane resins which are a mixture of polymeric compounds resulting from the reaction of a polyvalent isocyanate with a polyol and a mono- and/or diamine.
• the urea urethane resin is derived from a polyfunctional isocyanate, 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 selected from 2,4-toluene diisocyanate and/or m-xylylene diisocyanate.
• a polyfunctional isocyanate preferably selected from 1,4-tetram
• the urea urethane resin is derived from a polyol selected from polyoxyalkylenediols, particularly preferably from polyoxyethylene glycols, which in turn are preferably composed of at least 6, particularly preferably at least 8, particularly preferably at least 10, but preferably less than 26, particularly preferably less than 23 oxyalkylene units.
• Urea urethane resins which are particularly suitable according to the invention and are therefore preferred are obtainable by a first reaction of a diisocyanate, for example toluene-2,4-diisocyanate, with a polyol, for example a polyethylene glycol, to form NCO-terminated urethane prepolymers, after which further reaction takes place with a primary monoamine and/or with a primary diamine, for example m-xylylenediamine.
• a diisocyanate for example toluene-2,4-diisocyanate
• a polyol for example a polyethylene glycol
• NCO-terminated urethane prepolymers after which further reaction takes place with a primary monoamine and/or with a primary diamine, for example m-xylylenediamine.
• Urea urethane resins which have neither free nor blocked isocyanate groups are particularly preferred.
• urea urethane resins promote the formation of loose agglomerates of primary particles which are protected against further agglomeration and dissociate into primary particles when diluted, for example during contact in step (i), or when added to the acidic, aqueous composition in step (ii).
• urea urethane resins which have neither free or blocked isocyanate groups nor terminal amine groups are preferably used as thickeners.
• the thickener which is a urea urethane resin, therefore has an amine number of less than 8 mg KOH/g, particularly preferably less than 5 mg KOH/g, especially preferably less than 2 mg KOH/g, in each case determined according to the method as previously described for the organic polymeric compound (P2).
• an activating agent is accordingly preferred in which the totality of the polymeric organic compounds in the non-particulate component preferably has an amine number of less than 16 mg KOH/g, particularly preferably less than 10 mg KOH/g, especially preferably less than 4 mg KOH/g.
• the urea urethane resin has a hydroxyl number in the range from 10 to 100 mg KOH/g, particularly preferably in the range from 20 to 60 mg KOH/g, determined according to method Ader 01/2008:20503 from European Pharmacopoeia 9.0.
• a weight-average molar mass of the urea urethane resin in the range from 1000 to 10000 g/mol, preferably in the range from 2000 to 6000 g/mol is advantageous according to the invention and is therefore preferred, in each case determined experimentally as previously described in connection with the definition of a polymeric organic compound according to the invention.
• the activating aid is an aqueous dispersion which preferably has a pH in the range of 6.0 - 9.0 and particularly preferably contains no pH-regulating, water-soluble compounds with a pKa value of less than 6 or a pK B value of less than 5.
• the activating agent can also contain other auxiliary substances, for example selected from preservatives, wetting agents and defoamers, which are contained in the amount necessary for the respective function.
• auxiliary substances for example selected from preservatives, wetting agents and defoamers, which are contained in the amount necessary for the respective function.
• the proportion of auxiliary substances, particularly preferably of other compounds in the non-particulate component which are not thickeners, is less than 1% by weight.
• the activating aids in process steps (i) and (ii) are each based on identical water-dispersed, particulate components (P).
• the water-dispersed, particulate components (P) are already considered to be identical if the components (P1) and (P2) do not differ from one another in their chemical constitution, i.e. the water-dispersed, particulate components (P) of the respective aqueous dispersions contain the stoichiometrically identical phosphate of the same polyvalent cation and the same constitutional repeat units with regard to the polymeric organic compounds.
• wetting of metallic substrates with an activating agent prior to an activating zinc phosphating process can reduce the layer weights and at the same time save the amount of activating agent required to prepare an activating zinc phosphating bath.
• test panels (105x190 mm, Gardobond ® , Chemetall) made of cold-rolled steel (CRS), hot-dip galvanized steel (HDG) and aluminum (alloy AA6014) were each first wetted with an activating agent and immediately afterwards zinc phosphated.
• Table 1 lists the layer weights achieved in accordance with the process sequences listed there. It can be seen that pre-activation of the zinc surfaces leads to a significant reduction in the layer weight in the activating zinc phosphating (V1 vs. E1), which already occurs when the low-concentration aqueous dispersion is sprayed for activation wetting. When the concentration is increased by a factor of 10, a further reduction in the layer weight to around 2 g/m 2 occurs on the zinc surfaces, while a closed, homogeneous phosphate layer is still achieved (E1 vs. E2).
• the layer weight which is already well below 3 g/m 2 without pre-activation (CRS: V1), is then significantly reduced again with pre-activation by spraying and even brought to values below 2 g/m 2 (CRS: E1 vs. E2), without any loss of phosphating quality in the layer formation.
• the layer formation process on the The coating weight on the surfaces of aluminum is only slightly dependent on the respective process sequence and is in the range of 2 g/m 2 with or without pre-activation. Overall, the process according to the invention makes it possible to level out the layer weight deposits, which are still different on the different substrates during activated zinc phosphating.
• the two-stage process is also very effective with regard to the use of activating agents and, as the process sequence according to type E3 shows, can also be optimized in such a way that less activating agent needs to be used overall than with only activated zinc phosphating.
• the amount of activating agent in the zinc phosphate bath can be reduced to a fifth of the amount according to process sequence V1, and yet significantly lower layer weights are still achieved on HDG.
• Only the pre-activation of the zinc surfaces is required, and thus only a fraction of the activating agent needs to be used, which would otherwise have to be added to the zinc phosphate bath in a process sequence according to type V1 to maintain the phosphating quality.
• part of the activating agent that remains on the pre-activated zinc surfaces goes directly into the zinc phosphate bath with the components and helps to maintain the phosphating quality there, so that overall, the process according to the invention makes a very resource-saving process control for zinc phosphating accessible.

Landscapes

• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

Priority Applications (8)

Applications Claiming Priority (1)

Publications (1)

Family

ID=85172749

Family Applications (2)

Family Applications After (1)

Country Status (7)

Citations (5)

• 2023
  • 2023-02-02 EP EP23154613.6A patent/EP4411022A1/fr not_active Withdrawn
  • 2023-12-20 KR KR1020257028744A patent/KR20250142885A/ko active Pending
  • 2023-12-20 JP JP2025544892A patent/JP2026504448A/ja active Pending
  • 2023-12-20 EP EP23836773.4A patent/EP4658832A1/fr active Pending
  • 2023-12-20 CN CN202380096852.2A patent/CN121079451A/zh active Pending
  • 2023-12-20 WO PCT/EP2023/086847 patent/WO2024160449A1/fr not_active Ceased
• 2025
  • 2025-07-29 US US19/283,709 patent/US20250354269A1/en active Pending
  • 2025-08-01 MX MX2025009068A patent/MX2025009068A/es unknown

Patent Citations (5)

Also Published As

Similar Documents

Legal Events