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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
  • C23F11/18—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using inorganic inhibitors
  • C23F11/187—Mixtures of inorganic inhibitors
  • C23F11/188—Mixtures of inorganic inhibitors containing phosphates
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D13/00—Electrophoretic coating characterised by the process
  • C25D13/22—Servicing or operating apparatus or multistep processes
• • 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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/04—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in markedly acid liquids
• • 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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
  • C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
  • C23F11/173—Macromolecular compounds
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D13/00—Electrophoretic coating characterised by the process
  • C25D13/20—Pretreatment

Definitions

• the present invention relates to a method for the anti-corrosion pretreatment of a large number of components in series, in which each component in the series at least partially has surfaces of the metals zinc, iron and/or aluminum and undergoes a process step for zinc phosphating and is thereby brought into contact with an acidic aqueous composition to which such an amount of an activating aid has been added that is sufficient to ensure a coating weight of less than 5.5 g/m 2 on a merely cleaned and otherwise untreated hot-dip galvanized steel surface (Z).
• the activating aid is based on a water-dispersed, particulate component which is at least partially selected from hopeite, phosphophyllite, scholzite and/or hureaulite, and at least one polymeric organic compound.
• an acidic, aqueous composition for zinc phosphating is included, which is obtainable by adding a certain amount of a colloidal, aqueous solution containing the dispersed, particulate component to an acidic, aqueous composition containing zinc ions, phosphate ions and free fluoride.
• the layer-forming phosphating is a process that has been practiced and intensively studied for decades for the application of crystalline anti-corrosion coatings on metallic surfaces, in particular on materials made of the metals iron, zinc and aluminium.
• Zinc phosphating which is particularly well-established for corrosion protection, takes place in a layer thickness of a few micrometers and is based on corrosive pickling of the metallic material in an acidic, aqueous composition containing zinc ions and phosphates.
• an alkaline diffusion layer forms on the metal surface, which extends into the interior of the solution and within which poorly soluble crystallites form, which precipitate directly at the interface with the metallic material and continue to grow there.
• Water-soluble compounds which represent a source of fluoride ions, are often added to support the pickling reaction on materials made of the metal aluminum and to mask the bath poison aluminum, which in dissolved form interferes with the formation of layers on materials made of the metal.
• the zinc phosphating is adjusted in such a way that homogeneous, closed and compact crystalline coatings are achieved on the surfaces of the metals iron, zinc and aluminium. Otherwise, good corrosion protection and paint primer cannot be achieved. Homogeneous, closed coatings in zinc phosphating are usually reliably achieved from a layer weight of 2 g/m 2 .
• the pickling described above and the concentration of the active components in the zinc phosphating stage must be adjusted accordingly in order to ensure correspondingly high layer weights on the surfaces of the metals iron or steel, zinc and aluminum.
• the zinc phosphating in the prior art is always initiated with an activation of the metallic surfaces of the component to be phosphated.
• Activation is usually a wet-chemical process step that is conventionally brought into contact with colloidal, aqueous solutions of phosphates ("activation stage"), which are immobilized on the metal surface in the subsequent phosphating as a growth nucleus for the formation of the crystalline coating inside serve the alkaline diffusion layer, so that a high Causes a number density of growing crystallites and thus in turn a compact crystalline zinc phosphate layer is generated, which has excellent corrosion protection and, due to its high electrical penetration resistance, also excellent electrocoating properties.
• Suitable dispersions are colloidal, mostly neutral to alkaline, aqueous compositions based on phosphate crystallites which, in their crystal structure, exhibit only slight crystallographic deviations from the type of zinc phosphate layer to be deposited. That's how she teaches WO 98/39498 A1 in this connection, in particular, bivalent and trivalent phosphates of the metals Zn, Fe, Mn, Ni, Co, Ca and Al, phosphates of the metal zinc preferably being used for activation for subsequent zinc phosphating.
• An activation stage based on dispersions of bi- and trivalent phosphates requires a high level of process control in order to keep the activation performance constantly at an optimal level, especially when treating a series of metallic components.
• aqueous solution must lead to a deterioration in the activation performance.
• a deterioration is initially noticeable in increasing layer weights in the subsequent phosphating and finally leads to the formation of defective or inhomogeneous or less compact phosphate layers.
• the layer-forming zinc phosphating with upstream activation is therefore a multi-stage process that is complex to control in terms of process technology, which has also been resource-intensive to date, both in terms of the process chemicals and the energy to be expended.
• the WO 2019/238573 A1 addresses a resource-saving process for zinc phosphating and indirectly also a reduction in the complexity of the multi-stage process by presenting a particularly effective activation based on specifically dispersed bi- and trivalent phosphates, which produces a colloidal, aqueous solution based on bi- and trivalent phosphates and also already homogeneous, closed and very compact with a relatively low particulate content in the activation stage Allows zinc phosphate coatings, so that the material requirement is reduced due to the layer formation in the zinc phosphating.
• this complex profile of requirements can be met by maintaining the activation capacity of a pretreatment line for zinc phosphating by metering in an activating aid to the wet-chemical treatment stage of zinc phosphating.
• This makes it possible, at least partially or entirely, to dispense with an activation stage upstream of the wet-chemical treatment stage of zinc phosphating and in this way to conduct the overall process of zinc phosphating in a way that is less material and energy-intensive and at the same time to reduce procedural complexity in the form of the separate ones that have been absolutely necessary in the prior art decrease activation level.
• a pretreatment in series is when the components of the series each go through a process step for zinc phosphating according to the method according to the invention and are brought into contact with at least one bath liquid for zinc phosphating provided in a system tank, the individual components being brought into contact one after the other and is therefore separated in time.
• the system tank is the container in which the acidic aqueous composition is located for the purpose of zinc phosphating by means of a wet-chemical pre-treatment.
• the components can be brought into contact with the bath liquid of the system tank inside the system tank, for example by immersion, or outside of the system tank, for example by spraying or spraying on the bath solution stored in the system tank.
• the components treated according to the present invention can be any three-dimensional structure of any shape and design that originates from a manufacturing process, in particular semi-finished products such as strips, sheet metal, rods, pipes, etc. and composite structures assembled from the aforementioned semi-finished products, the semi-finished products preferably being assembled by gluing, Welding and / or flanging are connected to the composite structure.
• semi-finished products such as strips, sheet metal, rods, pipes, etc.
• composite structures assembled from the aforementioned semi-finished products the semi-finished products preferably being assembled by gluing, Welding and / or flanging are connected to the composite structure.
• a component then has at least one surface of the metals zinc, iron and/or aluminum if the metallic structure on this surface is composed of more than 50 at.% of one of the aforementioned metals up to a material penetration depth of at least one micrometer.
• the inventive property of the acidic aqueous composition for zinc phosphating on hot-dip galvanized steel surfaces is the growth of a zinc phosphate layer with a layer weight below 5.5 g/m 2 , preferably below 5.0 g/m 2 , particularly preferably below 4.5 g/m 2 (referred to below as "phosphating quality") is to be checked on merely cleaned and degreased (Z) substrates which are not subjected to any further wet-chemical pretreatment step before being brought into contact with the acidic aqueous composition of the method according to the invention.
• hot-dip galvanized steel (Z) is first prepared with an alkaline cleaner as 2% by weight Bonderite ® C-AK 1565 A and 0.2% by weight Bonderite ® C-AD 1270 in deionized water ( ⁇ 1 ⁇ Scm -1 ) at pH 11.0 and 55 °C for 5 minutes in immersion.
• the thus cleaned and degreased (Z) substrates are rinsed at room temperature with deionized water ( ⁇ 1 ⁇ Scm -1 ) and then fed to the process step of zinc phosphating in accordance with the selected process according to the invention.
• the selected method according to the invention means using exactly those process parameters such as temperature, duration and bath circulation for which the phosphating quality of the acidic aqueous composition should apply, ie the resulting target layer weights on hot-dip galvanized steel (Z) below 5.5 g/m 2 , preferably below 5.0 g/m 2 , particularly preferably below 4.5 g/m 2 .
• the layer weight on hot-dip galvanized steel (Z) increases by no 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 is guaranteed, in the invention Process to produce compact, crystalline zinc phosphate layers.
• an amount of an activation aid (D) is added that is sufficient under the selected conditions of the zinc phosphating process step in the process according to the invention, the property of the acidic aqueous composition, on a hot-dip galvanized steel surface (Z) a zinc phosphate layer with a layer weight of less than 5.5 g/m 2 , preferably less than 5.0 g/m 2 , particularly preferably less than 4.5 g/m 2 , maintaining this under the selected conditions of the method step the layer weight achieved during zinc phosphating in the process according to the invention increases by no more than 0.2 g/m 2 when the contact time with the acidic, aqueous composition is extended by 60 seconds.
• an activation aid (D) is added that is sufficient under the selected conditions of the zinc phosphating process step in the process according to the invention, the property of the acidic aqueous composition, on a hot-dip galvanized steel surface (Z) a zinc phosphate layer with a layer weight of less than 5.5 g/m 2 ,
• the phosphating quality is determined and monitored in the method according to the invention, in that hot-dip galvanized steel (Z), which has been cleaned and degreased as described above, also undergoes the zinc phosphating process step at regular intervals during the series treatment and is then subjected to a coating weight determination.
• hot-dip galvanized steel (Z) which has been cleaned and degreased as described above, also undergoes the zinc phosphating process step at regular intervals during the series treatment and is then subjected to a coating weight determination.
• the phosphating quality of the acidic, aqueous composition is ensured by metering in the activating agent (D), homogeneous, closed and compact crystalline zinc phosphate coatings are deposited on the components that have the surfaces of the metals zinc, iron and aluminum in the usual treatment times of 20 seconds to 5 minutes.
• the layer weight of zinc phosphate is determined within the scope of the present invention by detaching the zinc phosphate layer with aqueous 5 wt 5 min is brought into contact with a defined area of the phosphated material or component and subsequent determination of the phosphorus content in the same pickling solution with ICP-OES.
• the layer weight of zinc phosphate results from multiplying the surface-related amount of phosphorus by a factor of 6.23.
• the activating aid (D) is added to the acidic aqueous composition for zinc phosphating for the purpose of maintaining the phosphating quality in the zinc phosphating process step.
• the addition can be used to maintain the phosphating quality in the process Series treatment can be carried out by continuous or discontinuous dosing into the system tank. Continuous dosing is preferred when the pretreatment of the components in series follows immediately after one another and the decrease in the phosphating quality can be determined over time, so that a quantity of the activating agent can be continuously added over time.
• This process has the advantage that the phosphating quality does not have to be checked further after the start of the pre-treatment line and the determination of the material flows for the dosing of the activating aid and other active components, as long as the series treatment in terms of timing and condition of the components to be treated and the treatment parameters in the process step of Zinc phosphating remains unchanged.
• discontinuous dosing of the activation aid is advantageous and may even be indicated.
• the phosphating quality of the acidic aqueous composition is preferably monitored continuously or at defined time intervals and then a specified amount of the activation aid is metered in if the layer weight on hot-dip galvanized steel (Z) is a certain value below 5.5 g/m 2 , preferably below of 5.0 g/m 2 , particularly preferably below 4.5 g/m 2 .
• the continuous or quasi-continuous determination of the phosphating quality, which takes place 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 provides suitable proxy data for the layer weight of zinc phosphate, which is reliably measured on the components in a pre-treatment line and with the actual layer weight on the hot-dip galvanized parts Steel (Z) can be correlated.
• the crystallite size and thus the determination of the roughness by means of 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, however, are relatively larger, so that the roughness with the layer weight increases.
• the phosphating quality is already adequate in most cases if the activation aid (D) is metered in continuously or discontinuously in such an amount that is suitable, a stationary amount of preferably at least 0.001 g/kg, particularly preferably at least 0.005g/kg, more preferably maintaining at least 0.01 g/kg of particulate component (a) in the acidic aqueous composition during the pretreatment of the components in series.
• the present invention thus shows in a surprising way that the addition of an activating agent, as is known in the art and for example in WO 98/39498 A1 is described, the metal surfaces can be activated immediately with the acidic, aqueous zinc phosphating treatment solution, so that homogeneous, closed and compact crystalline zinc phosphate coatings with a high electrical penetration resistance grow on the metal surfaces.
• the present invention makes use of this effect by focusing on maintaining the phosphating quality in the series treatment of components by metering in the activating aid to the acidic, aqueous composition for zinc phosphating.
• the components of the series are particularly preferably not brought into contact with any colloidal, aqueous solution to activate the surfaces of the components for zinc phosphating before they are brought into contact with the acidic aqueous composition in the zinc phosphating process step, and the components of the series are very particularly preferably passed through before contacting no activation stage to activate the surfaces of the components for zinc phosphating.
• a cleaning and degreasing step cannot usually be dispensed with.
• at least the metallic surfaces of the components are cleaned and optionally degreased in a cleaning step before the zinc phosphating step.
• the cleaning is preferably carried out by bringing it into contact with an aqueous, preferably neutral or alkaline cleaning agent, the process step of zinc phosphating preferably immediately following the cleaning step with or without an intermediate rinsing step.
• the alkaline cleaning is characterized by the fact that the metal surfaces, in particular the surfaces that contain metallic aluminum, whether as a material or as an alloy component of hot-dip galvanized steel, are pickled, which leads to an additional standardization of the metal surfaces and is therefore advantageous for the Growth of homogeneous zinc phosphate coatings.
• the cleaning stage is preferably not carried out by bringing it into contact with an aqueous, preferably neutral or alkaline cleaner containing a particulate component comprising hopeite, phosphophyllite, scholzite and/or hureaulite or poorly soluble salts of the element Ti, since, as explained above, any activation of the metal surfaces before the zinc phosphating can be dispensed with according to the invention.
• a rinsing step after cleaning is optional and, in the context of the present invention, is used exclusively for the complete or partial removal of soluble residues, particles and active components that are carried over from a previous wet-chemical treatment step - here the cleaning and degreasing step - adhering to the component , from the component to be treated, without the rinsing liquid itself containing active components based on metallic or semi-metallic elements, which are consumed simply by bringing the metallic surfaces of the component into contact with the rinsing liquid.
• the rinsing liquid can only be city water or deionized water or, if necessary, it can also be a rinsing liquid which contains surface-active compounds to improve the wettability with the rinsing liquid.
• the phosphating quality in the method according to the invention on hot-dip galvanized steel is technically optimized, methods are naturally also preferred according to the invention in which the components of the series at least partially have surfaces of the metal zinc have, which are selected in particular from surfaces of hot-dip galvanized steel.
• the phosphating quality of the acidic, aqueous composition, which is maintained in the process according to the invention by adding the activating aid (D), is such that components that are manufactured in multimetal construction, such as automobile bodies, can also be zinc-phosphated with very good properties and also on very homogeneous, closed and compact zinc phosphate coatings are accessible on the surfaces of iron and aluminum.
• the components in the series also have surfaces made of the metal iron or, specifically for lightweight construction in bodywork production, additional aluminum.
• the components have surfaces of the metals zinc, iron and aluminum next to one another.
• the components are brought into contact with the acidic, aqueous composition for at least a period of time sufficient to deposit a layer weight of at least 1.0 g/m 2 on the zinc surfaces , since it is then ensured that a sufficiently homogeneous, closed zinc phosphate coating is formed on all metal surfaces of the components selected from zinc, iron and aluminum. Accordingly, preference is given to a method according to the invention in which a zinc phosphate layer with a layer weight of at least 1.0 g/m 2 , preferably at least 1.5 g/m 2 , is deposited on the surfaces of zinc.
• the layer weight of the zinc phosphate layer on the zinc surfaces of the component is preferably below 5.5 g/m 2 , preferably below 5.0 g/m 2 and particularly preferably below 4.5 g / m 2 lies.
• Activation aids (D) which can be used according to the invention, i.e. which maintain the phosphating quality when added to the acidic, aqueous composition of the zinc phosphating, are aqueous dispersions and thus contain a particulate component (a) in water-dispersed form which contains at least one particulate inorganic compound ( a1) consisting of phosphates of polyvalent metal cations at least partially is composed selected from hopeite, phosphophyllite, scholzite and/or hureaulite, and at least one polymeric organic compound (a2).
• the use of polyvalent metal cations in the form of phosphates is responsible for the good activation performance or suitability of the activating aid (D) to maintain the phosphating quality of the acidic aqueous composition for zinc phosphating, and they are therefore present in the activating aid (D) with a sufficiently high proportion should be included in the dispersed particulate component (a).
• the proportion of phosphates contained in the at least one particulate inorganic compound (a1) based on the dispersed particulate component (a) in the activation aid is preferably at least 25% by weight, particularly preferably at least 35% by weight, particularly preferably at least 40% by weight %, most preferably at least 45% by weight.
• the dispersed particulate component (a) of the activation aid (D) is the solids content that remains after drying the retentate of an ultrafiltration of a defined partial volume of the activation aid (D) with a nominal exclusion limit of 10 kD (NMWC, Nominal Molecular Weight Cut Off).
• the ultrafiltration is carried out with the supply of deionized water ( ⁇ 1 ⁇ Scm -1 ) until a conductivity below 10 ⁇ Scm -1 is measured in the filtrate.
• the inorganic particulate component in the activation aid (D) is in turn that which remains when the particulate component (a) obtained from the drying of the retentate of the ultrafiltration is heated in a reaction furnace at 900° C.
• the phosphates contained in the inorganic particulate component are determined directly from the acid digestion as the phosphorus content by means of atomic emission spectrometry (ICP-OES) after acid digestion of the same with aqueous 10% by weight HNO 3 solution at 25° C. for 15 minutes.
• ICP-OES atomic emission spectrometry
• the active components of the activation aid (D), which - as soon as they are added in sufficient quantities to the acidic aqueous composition for zinc phosphating - promote the formation of a homogeneous, closed and compact crystalline phosphate coating on the metal surfaces and in this sense activate the metal surfaces, are as already mentioned composed primarily 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 wholly particularly preferably at least partially selected from hopeite.
• the maintenance of the phosphating quality in the acidic, aqueous composition is therefore essentially based on the metered-in phosphates in particulate form contained in the activation auxiliary (D).
• hopeites stoichiometrically comprise Zn 3 (PO 4 ) 2 and the variants Zn 2 Mn(PO 4 ) 3 , Zn 2 Ni(PO 4 ) 3 , Zn 2 Ni(PO 4 ) 3 containing nickel and manganese, whereas phosphophyllite consists of Zn 2 Fe(PO 4 ) 3 , scholzite consists of Zn 2 Ca(PO 4 ) 3 and hureaulite consists of Mn 3 (PO 4 ) 2 .
• the existence of the crystalline phases hopeite, phosphophyllite, scholzite and/or hureaulite in the activation aid (D) can, after separating the particulate component (a) by means of ultrafiltration with a nominal exclusion limit of 10 kD (NMWC, Nominal Molecular Weight Cut Off) as described above and Drying of the retentate to constant mass at 105°C can be demonstrated using X-ray diffractometric methods (XRD).
• NMWC Nominal Molecular Weight Cut Off
• the activation aid (D) 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, based on the phosphate content of the inorganic particulate component, calculated as PO 4 , is contained.
• the activation aid (D) should preferably not additionally contain any titanium phosphates, since these do not have a positive effect on the phosphating quality when metered in.
• the proportion of titanium in the inorganic particulate component of the activation aid (D) is less than 0.01% by weight, particularly preferably less than 0.001% by weight, based on the activation aid (D).
• the activation aid (D) contains a total of less than 10 mg/kg, particularly preferably less than 1 mg/kg, of titanium.
• the polymeric organic compound (a2) which stabilizes the particulate component exerts a major influence on the effectiveness of the particulate component (a) metered in via the activation auxiliary (D). It is found that the selection of the polymeric organic compound is decisive for the degree of activation of the metal surfaces in the acidic aqueous zinc phosphating composition, which is known to be caused by the dispersed polyvalent phosphates is brought about and which, as the present invention shows, can surprisingly also take place at the same time as the layer formation.
• 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 variable, determined experimentally at 30° C. using size exclusion chromatography with a concentration-dependent refractive index detector and calibrated against polyethylene glycol standards. The average molar mass values are evaluated computer-aided using the strip method with a third-order calibration curve.
• Hydroxylated polymethacrylate is suitable as 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 eluent.
• the polymeric organic compound (a2) used to disperse the particulate inorganic compound (a1) is at least partly composed of styrene and/or an ⁇ -olefin having not more than 5 carbon atoms, the polymeric organic compound (a2) 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.
• Such polymeric organic compounds (a2) are therefore preferred according to the invention in the particulate component (a) of the activation aid.
• the ⁇ -olefin is preferably selected from ethene, 1-propene, 1-butene, isobutylene, 1-pentene, 2-methylbut-1-ene and/or 3-methylbut-1-ene and particularly preferably selected from isobutylene. It is clear to the person skilled in the art that the polymeric organic compounds (a2) contain these monomers as structural units in unsaturated form covalently linked to one another or to other structural units.
• Suitable commercially available representatives of polymeric organic compounds (a2) are Dispex® CX 4320 (BASF SE), a maleic acid/isobutylene copolymer modified with polypropylene glycol, Tego® Dispers 752 W (Evonik Industries AG). 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 polymeric organic compounds (a2) used for the colloidal stabilization of the particulate component (a) of the activation aid (D) preferably have polyoxyalkylene units, which in turn are preferably made up of 1,2-ethanediol and/or 1,2-propanediol, especially preferably of 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 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 (a2).
• the organic polymeric compounds (a2) also have imidazole units, preferably such that the polyoxyalkylene units of the polymeric organic compounds (a2) at least partially end-capped with an imidazole group, so that in the preferred embodiment terminal imidazole groups are present in the polyoxyalkylene side chain, the polyoxyalkylene units being covalently linked to the imidazole group preferably via a nitrogen atom of the heterocycle.
• the amine number of the organic polymeric compounds (a2) is at least 25 mg KOH/g, particularly preferably at least 40 mg KOH/g, but preferably less than 125 mg KOH/g, particularly preferably less than 80 mg KOH / g, so that in a preferred embodiment all of the polymeric organic compounds in the particulate component (a) of the activating aid have these preferred amine numbers.
• the amine number is determined in each case by weighing approximately 1 g of the respective reference quantity - organic polymeric compounds (a2) or all of the polymeric organic compounds in the particulate component (a) - in 100 ml of ethanol, with 0.1 N HCl standard solution titrated against the indicator bromphenol blue until the color changes to yellow at a temperature of the ethanolic solution of 20 °C.
• the amount of standard HCl solution consumed in milliliters multiplied by the factor 5.61 divided by the exact mass of the sample in grams corresponds to the amine number in milligrams of KOH per gram of the respective reference value.
• the polymeric organic compounds (a2) preferably also all of the polymeric organic compounds in the particulate component (a), 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, more preferably less than 70 mg KOH/g to ensure a sufficient number of polyoxyalkylene units.
• the polymeric organic compounds (a2) preferably also all of the polymeric organic compounds in the particulate component (a), have a hydroxyl number of less than 15 mg KOH/g, particularly preferably less than 12 mg KOH/g, particularly preferably less than 10 mg KOH/g, determined in each case according to method A of 01/2008:20503 from European Pharmacopoeia 9.0.
• the proportion of the polymeric organic compounds (a2), preferably all of the polymeric organic compounds in the particulate component (a), based on the particulate component (a) is at least 3% by weight, more preferably at least 6% by weight, but preferably does not exceed 15% by weight.
• the dispersed particulate component (a) of the activation aid (D) is the solids content that remains after drying the retentate of an ultrafiltration of a defined partial volume of the activation aid (D) with a nominal exclusion limit of 10 kD (NMWC, Nominal Molecular Weight Cut Off).
• the ultrafiltration is under Feeding of deionized water ( ⁇ ⁇ 1 ⁇ Scm -1 ) carried out until a conductivity below 10 ⁇ Scm -1 is measured in the filtrate.
• the activation aid (D) preferably contains no more than 40% by weight of particulate component (a) based on the agent, otherwise the stability of the dispersion and the procedural manageability for continuous or discontinuous dosing of the agent to the acidic aqueous composition of the zinc phosphating agent Dosing pumps are no longer guaranteed or at least expensive. This applies in particular with regard to the overall low amounts of particulate constituents (a) required to maintain the phosphating quality of a reference amount of the acidic aqueous composition for zinc phosphating. On the other hand, it is advantageous if the activation aid is provided as a dispersion which is as stable as possible and at the same time as highly concentrated as possible.
• activation aids (D) which contain at least 5% by weight, but preferably not more than 30% by weight % of particulate component (a) based on the composition.
• the activation aid (D) can in the process according to the invention also have a D50 value of be characterized more than 10 microns, which is correspondingly preferred.
• the agglomerates of the dispersed particles contained in the dispersion cause the thixotropic flow properties, which are favorable for the activating aid (D) to be able to be handled.
• the tendency of the agglomerates to be highly viscous at low shear favors their long shelf life, while the loss of viscosity at shear conditions their pumpability.
• the D50 value or the D90 value denotes the particle diameter which 50% by volume or 90% by volume, respectively, of the particulate components present in the aqueous dispersion do not exceed.
• the particle size distribution is measured within 120 seconds of adding the dispersion to the dilution volume.
• the presence of a thickener can be advantageous for preventing the irreversible agglomeration of primary particles of the particulate component (a), particularly when the activation aid (D) is present as the concentrated dispersion described above.
• the activating aid (D) contains a thickener, preferably in an amount which gives the activating aid (D) a maximum dynamic viscosity at a temperature of 25° C. in the shear rate range from 0.001 to 0.25 reciprocal seconds at least 1000 Pa ⁇ s, but preferably below 5000 Pa ⁇ s, and preferably results in shear-thinning behavior at 25° C.
• 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.
• ⁇ ⁇ 1 ⁇ Scm -1 deionized water
• the viscosity reading is then read immediately within 5 seconds after application of 60 rpm shear by spindle number 2.
• the activation aid (D) 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 still preferably being polymers organic compounds in the non-particulate component of the aqueous dispersion does not exceed 4% by weight (based on the dispersion).
• the non-particulate component is the solids content of the aqueous dispersion in the permeate of the ultrafiltration already described after it has been dried to constant mass at 105° C.—ie the solids content after the particulate component has been separated off by means of 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 represent a mixture of polymeric compounds resulting from the reaction of a polyfunctional isocyanate with a polyol and a mono- and/or diamine.
• the urea urethane resin is derived from a polyhydric 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 polyhydric isocyanate preferably selected from 1,4-te
• the urea-urethane resin is derived from a polyol selected from polyoxyalkylene diols, 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 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, followed by further reaction 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
• such urea-urethane resins promote the formation of loose agglomerates of primary particles, which are protected against further agglomeration and, when metered into the acidic, aqueous composition for zinc phosphating, dissociate into primary particles.
• 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, particularly preferably less than 2 mg KOH/g, determined in each case according to the method as described above for the organic polymeric compound (a2).
• an activation aid is accordingly preferred in which the 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, particularly 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 A of 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 therefore preferred, in each case determined experimentally as before in connection with the inventive definition of a polymeric organic connection described.
• the activating aid (D) is an aqueous dispersion which preferably has a pH in the range of 6.5-8.0 and particularly preferably no pH-regulating, water-soluble compounds with a pK a value of less than 6 or pK B - contains a value less than 5.
• the activating aid (D) can also contain other auxiliaries, for example selected from preservatives, wetting agents and defoamers, which are present in the amount required for the particular function.
• the proportion of auxiliaries, particularly preferably of other compounds which are not thickeners, in the non-particulate component is preferably less than 1% by weight.
• the amount of phosphate ions includes orthophosphoric acid and the anions of the salts of orthophosphoric acid dissolved in water, calculated as PO 4 .
• the proportion of the free acid in points in the acidic aqueous composition of the zinc phosphating of the process according to the invention is preferably at least 0.4, but preferably not more than 3.0, particularly preferably not more than 2.0.
• the percentage of free acid in points is determined by diluting a 10 ml sample volume of the acidic aqueous composition to 60 ml and titrating with 0.1 N sodium hydroxide solution to pH 3.6. The consumption of ml of sodium hydroxide indicates the number of free acid points.
• the preferred pH of the acidic aqueous composition is usually above 2.5, particularly preferably above 2.7, but preferably below 3.5, particularly preferably below 3.3.
• the "pH value" as used in the context of the present invention corresponds to the negative decadic 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 zinc phosphating layer forming process.
• components including surfaces of zinc and surfaces of iron or aluminum are to be zinc-phosphated in a layer-forming manner, as is necessary, for example, in the zinc phosphating of automobile bodies that are at least partially made of aluminum, it is advantageous if the amount of free fluoride in of the acidic aqueous composition is at least 0.5 mmol/kg, particularly preferably at least 2 mmol/kg.
• the concentration of free fluoride should not exceed values above which the phosphate coatings have loose adhesions that can be easily wiped off, since this defect can also be caused by an increased dosage of activation aid (D) or by an increased stationary amount of particulate components (a) in of the acidic aqueous composition for zinc phosphating often cannot be compensated. It is therefore advantageous and therefore preferred if, in the method according to the invention, the concentration of free fluoride in the acidic aqueous composition of the zinc phosphating below 15 mmol/kg, particularly preferably below 10 mmol/kg and particularly preferably below 8 mmol/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 for 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.
• the source of free fluoride in a phosphating according to the present invention is therefore preferably selected from hydrofluoric acid and its water-soluble salts and/or complex fluorides of the elements Zr, Ti and/or Si.
• Hydrofluoric acid salts are water-soluble in the context of the present invention if their solubility in deionized water ( ⁇ Scm -1 ) at 60° C. is at least 1 g/L calculated as F.
• the source of free fluoride in such methods according to the invention is at least partially selected from complex fluorides of the element Si, in particular from hexafluorosilicic acid and its salts.
• complex fluorides of the element Si in particular from hexafluorosilicic acid and its salts.
• Those skilled in the art of phosphating understand the formation of specks as the phenomenon of 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 in the process according to the invention for more rapid layer formation. These are preferably selected from 2-hydroxymethyl-2-nitro-1,3-propanediol, nitroguanidine, N-methylmorpholine-N-oxide, nitrite, hydroxylamine and/or hydrogen peroxide.
• nitroguanidine or hydroxylamine is used as an accelerator, so that nitroguanidine or Hydroxylamine, in particular nitroguanidine, in terms of a particularly low use of substances in the activation aid Maintaining the phosphating quality, are particularly preferred as accelerators in the acidic aqueous composition in the process of the invention.
• an embodiment is particularly preferred in which less than 10 ppm of nickel and/or cobalt ions are contained in the acidic aqueous composition for zinc phosphating in the process according to the invention.
• the zinc phosphating follows with or without an intermediate rinsing and/or drying step, but preferably with a rinsing step but without a drying step, followed by a dip coating or powder coating, particularly preferably an electro-dip coating, particularly preferably a cathodic electro-dip coating, which preferably in addition the dispersed resin, which preferably comprises an amine-modified polyepoxide, contains water-soluble or water-dispersible salts of yttrium and/or bismuth.

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• 2020
  • 2020-09-04 EP EP20194512.8A patent/EP3964606A1/de not_active Withdrawn
• 2021
  • 2021-08-25 EP EP21762057.4A patent/EP4208585A1/de active Pending
  • 2021-08-25 WO PCT/EP2021/073476 patent/WO2022048963A1/de active Application Filing
  • 2021-08-25 CN CN202180054117.6A patent/CN116096945A/zh active Pending
  • 2021-08-25 MX MX2023002586A patent/MX2023002586A/es unknown
  • 2021-08-25 KR KR1020237007293A patent/KR20230061381A/ko active Search and Examination
  • 2021-08-25 JP JP2023514888A patent/JP2023540976A/ja active Pending
• 2023
  • 2023-02-24 US US18/174,102 patent/US20230220559A1/en active Pending

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