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
  • C23C22/364—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
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  • 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
• • 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
• • 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
  • C23C22/40—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 molybdates, tungstates or vanadates
• • 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
  • C23C22/78—Pretreatment of the material to be coated
  • C23C22/80—Pretreatment of the material to be coated with solutions containing titanium or zirconium compounds
• • 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
  • C23C22/82—After-treatment
  • C23C22/83—Chemical after-treatment
• • 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
  • C23C22/40—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 molybdates, tungstates or vanadates
  • C23C22/44—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 molybdates, tungstates or vanadates containing also fluorides or complex fluorides
• • 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
  • C23C2222/00—Aspects relating to chemical surface treatment of metallic material by reaction of the surface with a reactive medium
  • C23C2222/20—Use of solutions containing silanes

Definitions

• the present invention relates to the corrosion-protective treatment of composite metal structures containing metallic surfaces of aluminum, zinc and possibly iron in a multi-stage process.
• the process according to the invention enables the selective zinc phosphating of the zinc and iron surfaces of the composite metal construction without depositing significant amounts of zinc phosphate on the aluminum surfaces.
• the aluminum surface is in a subsequent process step for passivation with e.g. conventional acidic and optionally silane-containing passivation compositions are available which generate a homogeneous, corrosion-protecting thin passive layer.
• the present invention also relates to a zinc phosphating composition containing water-soluble inorganic compounds of boron in an amount sufficient to suppress speckling but which does not exceed values for which the zinc phosphating loses its selectivity for the zinc and iron surfaces of the composite metal construction.
• German published patent application DE 19735314 proposes a two-stage process in which initially a selective phosphating of the steel and galvanized steel surfaces of a likewise aluminum surfaces having body and then treatment of the body with a Passivitationswished for corrosion-protective treatment of Alumi- niummaschine the body.
• the selective phosphating is achieved by decreasing the pickling effect of the phosphating solution.
• DE 19735314 teaches phosphating solutions with a free fluoride content of less than 100 ppm, wherein the source of the free fluoride is formed exclusively by water-soluble complex fluorides, in particular hexafluorosilicates in a concentration of 1 to 6 g / l.
• the prior art discloses other two-stage pretreatment processes which also conceptually follow the deposition of a crystalline phosphate layer on the steel and optionally galvanized and alloy-galvanized steel surfaces in the first step and the passivation of the aluminum surfaces in a further subsequent step.
• These methods are disclosed in the documents WO 1999/012661 and WO 2002/066702.
• the processes disclosed therein are carried out in such a way that, in a first step, selective phosphating of the steel or galvanized steel surfaces takes place, which is also retained in the post-passivation in a second process step, while no phosphate crystals are formed on the aluminum surfaces.
• the selective phosphating of the steel and galvanized steel surfaces is achieved by a temperature-dependent limitation of the proportion of free fluoride ions in the phosphating solutions, whose free acid contents are set in a range of 0 to 2.5 points.
• the international application WO 2008/055726 discloses an at least one-step process for the selective phosphating of steel and galvanized steel surfaces of a composite construction comprising aluminum parts.
• This publication teaches phosphating solutions containing water-soluble inorganic compounds of the elements zirconium and titanium, the presence of which successfully prevents the phosphating of the aluminum surfaces.
• European application EP 2588646 discloses a process for the selective phosphating of steel and galvanized steel in metallic components which also have aluminum surfaces. This process also avoids the formation of phosphate crystal nests on the aluminum surfaces and specks on the galvanized steel surfaces.
• silicon is added to the zinc phosphating composition in the form of water-soluble inorganic compounds.
• phosphate crystal nests is understood by the person skilled in the art to mean the isolated and locally limited deposition of phosphate crystals on metal surfaces (here: aluminum surfaces). Such "crystal nests" are trapped by a subsequent coating primer and represent in-homogeneities in the coating, which both disturb the uniform visual impression of the painted surfaces and can also cause punctiform paint damage.
• speckling one skilled in the phosphating art understands 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 speckling is caused by a locally increased pickling rate of the substrate. Such point defects in the phosphating can Starting point for the corrosive delamination of subsequently applied organic paint systems, so that the occurrence of specks in practice is largely to be avoided.
• cryolite precipitation deposition of solid Na ß AIFe and / or K3AIF6 on the surface of the composite metal structures, in particular on the aluminum parts, causes a lubricating paper-like nature of this surface, which is undesirable because they are down to the surface of the finished painted Constructions continues.
• the result is painting defects that can only be eliminated with great effort by, for example, grinding the affected areas. This, of course, involves corresponding work effort and higher costs.
• the cryolite precipitation takes place according to the following formula:
• the sodium ions in the phosphating composition originate from additives such as, in particular, additives and / or accelerators.
• additives are mainly sodium fluoride, sodium nitrate, sodium phosphate and sodium hydroxide to name as accelerators, especially sodium nitrite.
• accelerators especially sodium nitrite.
• These additives are added to the bath depending on the situation and available bathing parameters.
• the aluminum ions were leached out of the aluminum parts of the composite metal constructions in the acidic environment of the phosphating bath composition.
• a certain minimum amount of free fluoride (fluoride ions) in the phosphating bath is necessary to ensure adequate deposition kinetics for the zinc phosphate layer on the surfaces of iron and zinc of the composite metal structure, in particular because of the simultaneous treatment of the aluminum surfaces of the composite metal structure aluminum Io - enter the zinc phosphating composition (see above), which in turn, in an uncomplexed form, interferes with or even prevents the formation of a uniform, homogeneous zinc phosphate layer on the iron and zinc parts of the composite construction.
• the free fluoride can also originate from fluoro complexes, from which it is released in equilibrium reactions.
• a poisoning of the phosphating bath by titanium, zirconium and / or hafnium may be due in particular to encrusted conveyor systems for the composite metal constructions or in pre-adjusted aluminum parts of the constructions.
• the crusts (eg phosphate crusts or non-baked coating layers) on the conveyor systems contain titanium, zirconium and / or hafnium.
• the latter are derived from the phosphatization (see step (I)) of the composite metal constructions subsequent passivation (see step (II)) with titanium, zirconium and / or hafnium-containing water-soluble compounds and are absorbed by the crusts due to their porosity. Since the conveyors run in a circle, the crusts in the passivation bath, which are exposed to titanium, zirconium and / or hafnium, are again exposed to the acid phosphating composition in the phosphating bath. Titanium, zirconium and / or hafnium partially dissolve there.
• the aluminum parts of composite metal constructions are often pre-passivated, ie they are already provided with a passivation layer containing titanium, zirconium and / or hafnium, which has already been applied to them by the supplier of the aluminum parts.
• step (II) in a second step comprises applying to the composite metal structure an aqueous acidic passivating composition having a pH in the range of 2.0 to 5.5, the acidic passivating composition on the parts of zinc and Iron does not dissolve more than 50% of the crystalline zinc phosphate, but forms a passive layer on the aluminum parts which does not constitute a surface-covering crystalline phosphate layer, the zinc phosphating composition in step (I) containing sodium and / or potassium ions and aluminum Contains ions,
• step (I) has a temperature in the range of 20 to 65 ° C and contains a content of free fluoride which is at least 5 mg / l but not greater than 200 mg / l,
• the score of the free acid with KCI addition in the zinc phosphating composition is at least 0.6 points.
• a “composite metal construction” in the sense of the present invention is a mixed component metallic component, in particular a body.
• the composite metal construction may also have surfaces of other metals and / or surfaces of non-metals, in particular of plastics.
• the material "aluminum” also means its alloys.
• the material zinc also comprises zinc alloys, for example zinc-magnesium alloys, and galvanized steel and alloy-galvanized steel, while the inclusion of iron also includes iron alloys, in particular steel. Alloys of the aforementioned materials have a Fremdatomanteil of less than 50 wt .-%.
• aqueous composition herein is meant a solution or dispersion which, for the most part, i. to more than 50 wt .-%, preferably more than 70% by weight, particularly preferably more than 90 wt .-% (based on the totality of the solvents contained, dispersion media) contains water as a solvent or dispersion medium.
• the aqueous composition can therefore contain not only dissolved but also dispersed constituents.
• it is a solution, i. to such a composition containing only small amounts of dispersed ingredients, preferably no dispersed ingredients at all, but only or almost only dissolved components.
• a “passive layer” in the sense of the present invention is a passivating, i. Corrosion-protective, inorganic or mixed inorganic-organic thin-film coating, which is not a closed crystalline phosphate layer.
• passive layers may consist, for example, of oxide compounds of titanium, zirconium and / or hafnium.
• water-soluble compounds is meant both a water-soluble compound and two or more water-soluble compounds.
• step (I) of the present process zinc phosphate layers with an area-related coating weight of preferably at least 1 on these surfaces, 0 g / m 2, more preferably of at least 2.0 g / m 2, but preferably not more than 4.0 g / m 2 deposited.
• the coating of zinc phosphate is determined for all surfaces of the composite metal construction by means of gravimetric differential weighing on test plates of the individual metallic materials of the respective composite metal construction.
• steel sheets immediately after a step (I) for 5 minutes with an aqueous solution of 9 wt .-% EDTA, 8.7 wt .-% NaOH and 0.4 wt .-% triethanolamine at a temperature of 70 ° C in Contact and freed in this way from the zinc phosphate layer.
• a corresponding test sheet is immediately after one step (I) for 4 minutes with an aqueous solution of 20 g / l (NH 4) 2Cr 2 0 7 and 27.5 wt .-%.
• NH3 brought at a temperature of 25 ° C in contact and freed in this way from the zinc phosphate layer.
• aluminum sheets are brought into contact with an aqueous 65% strength by weight HNO 3 solution at a temperature of 25 ° C. for 15 minutes immediately after step (I) and are freed from zinc phosphate portions accordingly.
• the difference in weight of the dry metal sheets after this respective treatment for weight of the same dry untreated metal sheet immediately before the step (I) corresponds to the coating of zinc phosphate according to this invention.
• step (II) not more than 50% of the crystalline zinc phosphate layer is dissolved on the steel and galvanized and / or alloy-galvanized steel surfaces can also be reconstructed on the basis of test sheets of the individual metallic materials of the respective composite metal construction.
• the test panels of steel, galvanized or alloy-galvanized steel phosphated according to step (II) of the process according to the invention are blown dry with compressed air after a rinsing step with deionized water and then weighed.
• step (II) of the process according to the invention is then brought into contact with the acidic passivation composition in accordance with step (II) of the process according to the invention, then rinsed with deionized water, blown dry with compressed air and then weighed again.
• the zinc phosphating of the same test sheet is then treated with an aqueous solution of 9% by weight EDTA, 8.7% by weight NaOH and 0.4% by weight triethanolamine or with an aqueous solution of 20 g / l (NH 4 ) 2 Cr 2 0 7 and 27.5 wt .-% NH 3 completely removed as described above and weighed the dried test sheet once more. From the weighing differences of the test sheet, the percentage loss of phosphate layer in step (II) of the method according to the invention is now determined.
• the free acid with KCI additive (FS, KCl) of the zinc phosphating composition in points in step (I) of the method according to the invention is determined as follows (see: W. Rausch "The phosphating of metals", Eugen G. Leuze Verlag, 3rd edition , 2005, Chapter 8.1, pp. 333-334):
• 10 ml of the phosphating composition are pipetted into a suitable vessel, for example a 300 ml Erlenmeyer flask. If the phosphating composition contains complex fluorides, 6-8 g of potassium chloride are added to the sample. Then, using a pH meter and an electrode, it is titrated with 0.1 M NaOH to a pH of 4.0. The consumed amount of 0.1 M NaOH in ml per 10 ml of the phosphating composition gives the value of the free acid with KCI additive (FS, KCl) in points.
• KCI additive FS, KCl
• the zinc phosphating composition in the step (I) preferably has a temperature in the range of 30 to 60 ° C, more preferably 35 to 55 ° C.
• the concentration of free fluoride in the zinc phosphating composition is determined in the method according to the invention by means of a potentiometric method.
• a sample volume of the zinc phosphating composition is taken and the activity of the free fluoride ions is determined with any commercial fluoride-selective potentiometric single-rod measuring chain after calibration of the combination electrode by means of fluoride-containing standard solutions without pH buffering. Both the calibration of the combination electrode and the measurement of the free fluoride are carried out at a temperature of 20 ° C.
• the zinc phosphating composition therefore has a free fluoride content of at least 5 mg / l but not greater than 200 mg / l, preferably at least 10 mg / l but not greater than 200 mg / l, more preferably at least 20 mg / l but not greater than 175 mg / l, more preferably at least 20 mg / l but not greater than 150 mg / l, more preferably at least 20 mg / l but not greater than 135 mg more preferably is at least 20 mg / L, but is not greater than 120 mg / L, more preferably at least 50 mg / L but not greater than 120 mg / L, and most preferably at least 70 mg / L is but not greater than 120 mg / l.
• the total fluoride content (F tot ) of the zinc phosphating composition is preferably in the range of 0.01 to 0.3 mol / l, more preferably 0.02 to 0.2 mol / l.
• the complex-bound fluoride is the fluoride bound to Si or B but also to Al and further complexes.
• the single fluoride is the non-complexed fluoride and is composed of the identifiable by Einstabmesskette free fluoride, ie the unbound fluoride, and the HF bound fluorine together.
• step (I) of the process according to the invention the higher the content of sodium and / or potassium ions, aluminum ions and free fluoride in the zinc phosphating composition in step (I) of the process according to the invention, the stronger the cryolite precipitation on the surface of the composite metal structures, in particular on the aluminum parts.
• the content of sodium and / or potassium ions (calculated as sodium) in the range of 1 to 4 g / l, in particular from 2 to 3 g / l and the content of free fluoride in the range of 50 to 150 mg / l In particular, from 70 to 120 mg / l can be in the presence of aluminum ions, the Kry- olithpositionlung by the presence of boron in the form of water-soluble inorganic compounds, in particular in the form of fluoroborates such as HBF 4 , reduce particularly effective.
• the zinc phosphating composition preferably has a concentration of boron in the form of water-soluble inorganic compounds calculated as BF 4 in the range of 0.08 to 2.5 g / l, more preferably 0.08 to 2 g / l, more preferably 0.25 to 2 g / l, more preferably from 0.5 to 1, 5 g / l and most preferably from 0.8 to 1, 2 g / l on.
• water-soluble inorganic compounds containing boron additionally acts to prevent the formation of specks on the zinc surfaces.
• the upper limit of 3.2 g / l calculated as BF 4 is on the one hand due to the economy of the process and on the other hand, that the process control is made difficult by such high concentrations of water-soluble inorganic compounds containing boron, since the formation of Phosphate crystal nests on the aluminum surfaces can only be pushed back to a lesser extent by increasing the free acid content.
• the crystal nests require punctiform elevations which have to be ground for an optically uniform lacquering of the composite metal construction, for example an automobile bodywork, desired by the customer.
• the concentration of boron in the form of water-soluble inorganic compounds calculated as BF 4 as a critical parameter is decisive for the success of the process according to the invention. If a concentration of 2.0 g / l is exceeded, the formation of at least individual zinc phosphate crystal nests on the aluminum surfaces already takes place.
• step (I) of the process according to the invention zinc phosphating compositions are used in which the concentration of boron in the form of water-soluble inorganic compounds has a value of 3.2 g / l, particularly preferably a value of 2.0 g / l. each calculated as BF 4 - does not exceed.
• the proportion of boron according to the invention in the form of water-soluble inorganic compounds is sufficient to prevent the formation of specks on the parts of zinc treated according to the invention.
• Water-soluble inorganic compounds containing boron which are preferred in the process according to the invention are fluoroborates, more preferably HBF 4 , (NH 4 ) BF 4 , LiBF 4 and / or NaBF 4 .
• the water-soluble fluoroborates are also suitable as a source of free fluoride and therefore serve the complexation of trivalent aluminum cations introduced into the bath solution, so that the phosphating remains ensured on the surfaces of steel and galvanized and / or alloy-galvanized steel.
• step (I) of the process according to the invention When using fluoroborates in phosphating solutions in step (I) of the process according to the invention, it must of course always be ensured that the concentration of boron in the form of water-soluble inorganic compounds calculated as BF 4 is 3.2 g / l according to claim 1 does not exceed the present invention.
• the zinc phosphating composition in step (I) also has a certain content of water-soluble inorganic compounds containing silicon.
• the latter can, for example, have been incorporated into the phosphating composition from previous process steps or-with a high silicon content of the aluminum parts-can also originate from the composite metal constructions.
• a content of inorganic compounds containing silicon is, for the purposes of the present invention, first of all undesirable, since this enhances the cryolite precipitation on the surface of the composite metal structures, in particular on their aluminum parts, which can be explained as follows:
• fluorosilicates such as hexafluorosilicate
• fluoride ions free fluoride
• fluoroborates such as tetrafluoroborate
• a content of inorganic compounds containing silicon is secondarily undesirable since it has now surprisingly been found that a zinc phosphating bath composition containing free silicon fluoride in the form of water-soluble inorganic compounds has much more titanium, zirconium and / or hafnium encrusted conveyor systems for the composite metal structures and / or the pre-passivated aluminum parts of the constructions can lead and thus lead to a much greater poisoning of the phosphating by titanium, zirconium and / or hafnium, as those having boron in the form of water-soluble inorganic compounds.
• a content of inorganic compounds containing silicon is undesirable, since sparingly soluble precipitates form in the presence of potassium ions, in particular in the case of fluorosilcates such as H2S1F6.
• the formation of such precipitates is as undesirable as the precipitation of cryolite.
• Potassium ions as cations in salts for adjustment of the bath parameters, such as in phosphates, hydroxides and fluorides, compared to sodium ions is advantageous since K3AIF6 is more soluble than Na ß Aife and thus less cryolite is precipitated.
• ammonium ions which may be present in the zinc phosphating composition also have this advantage (good solubility of (NH 4 ) 3AIF 6), they are more environmentally hazardous in wastewater than potassium ions.
• the formation of sparingly soluble, potassium-containing precipitates can not be determined for corresponding boron-containing compounds, in particular in the case of fluoroborates such as HBF 4 .
• the content of inorganic compounds containing silicon is therefore preferably below 25 mg / l, more preferably below 15 mg / l, more preferably below 5 mg / l and most preferably below 1 mg / l.
• the zinc phosphating composition in step (I) preferably has a KCI addition free acid score in the range of from 0.6 to 3.0 points, preferably from 0.8 to 3.0 points, more preferably from 1.0 to 3.0 points, and most preferably from 1, 0 to 2.5 points. Maintaining the preferred ranges for the free acid ensures on the one hand a sufficient deposition kinetics of the phosphate layer on the selected metal surfaces and on the other hand prevents unnecessary pickling of metal ions, which in turn requires intensive monitoring or processing of the phosphating bath to avoid the Precipitation of sludges or disposal thereof in the continuous operation of the inventive method requires.
• the total acid (GS) in the phosphating composition in step (I) of the process according to the invention should be in the range from 10 to 50, more preferably from 15 to 40 and particularly preferably from 20 to 35 points.
• Fischer's total acidity should be in the range of 10 to 30, more preferably 12 to 25, and most preferably 15 to 20 points, while the S value is in the range of 0.04 to 0.20, more preferably from 0.05 to 0.15, and more preferably from 0.06 to 0.12.
• FS free acid
• GSF Fischer's total acidity
• GSF Fischer's total acidity
• GS total acidity
• S-value S-value
• a suitable vessel for example into a 300 ml Erlenmeyer flask.
• 150 ml of deionized water are added.
• titrate with 0.1 M NaOH to a pH of 4.7.
• the consumed amount of 0.1 M NaOH in ml per 10 ml of the diluted phosphating composition gives the value of the free acid (diluted) (FS (dil.)) In points.
• the dilute phosphating composition is titrated to pH 8.9 after addition of potassium oxalate solution using a pH meter and electrode with 0.1 M NaOH.
• the consumption of 0.1 M NaOH in ml per 10 ml of the diluted phosphating composition gives the total Fischer acid (GSF) in points.
• the total acid (GS) is the sum of the divalent cations present as well as free and bound phosphoric acids (the latter being phosphates). It is determined by the consumption of 0.1 M NaOH using a pH meter and an electrode. For this purpose, 10 ml of the phosphating composition are pipetted into a suitable vessel, for example a 300 ml Erlenmeyer flask, and diluted with 25 ml of demineralized water. It is then titrated with 0.1 M NaOH to a pH of 9. The consumption in ml per 10 ml of the diluted phosphating composition corresponds to the total acid score (GS).
• S value stands for the ratio of the free acid with KCI additive to the total acid according to Fischer, ie (FS, KCl): GSF, and is obtained by dividing the value of the free acid with KCI additive (FS, KCl) by the value of total acid according to Fischer (GSF).
• the phosphating composition in step (I) preferably has a pH in the range of 2.5 to 3.5.
• zinc phosphating compositions are preferred in step (I) of the process according to the invention, which total not more than 20 ppm, preferably no more than 15 ppm, more preferably not more than 10 ppm, more preferably not more than 5 ppm and most preferably not more than 1 ppm total of water-soluble compounds of zirconium, titanium and / or hafnium, based on the elements zirconium, Titanium and / or hafnium and in particular preferably no water-soluble compounds of zirconium, titanium and / or hafnium.
• step (i) of the process according to the invention is completely dispensed with.
• poisoning of the phosphating bath by titanium, zirconium and / or hafnium can be caused, above all, by encrusted conveying systems for the composite metal structures or in pre-passivated aluminum parts of the structures.
• the content of boron in the form of water-soluble inorganic compounds can reduce the poisoning of the phosphating bath by titanium, zirconium and / or hafnium.
• titanium and / or zirconium is stabilized by the high content of free fluoride. It comes to the formation of the fluorocomplexes of titanium and / or zirconium. By lowering the content of free fluoride, titanium and / or zirconium is destabilized in its solubility, precipitates and thus no longer poisoning of the phosphatizing bath.
• the zinc phosphating composition therefore has a free fluoride content of at least 5 mg / l but not greater than 200 mg / l, preferably at least 10 mg / l but not greater than 200 mg / l, more preferably at least 20 mg / l but not greater than 175 mg / l, more preferably at least 20 mg / l but not greater than 150 mg / l, more preferably at least 20 mg / l but not greater than 135 mg more preferably is at least 20 mg / L, but is not greater than 120 mg / L, more preferably at least 50 mg / L but not greater than 120 mg / L, and most preferably at least 70 mg / L is but not greater than 120 mg / l.
• the conveyor systems for the composite metal constructions have crusts containing titanium, zirconium and / or hafnium and preferably from the subsequent phosphatization in step (I) passivation of the composite metal structures with titanium, zirconium and / or Haf - water-soluble compounds containing sodium in step (II) come.
• the conveyor systems preferably run in a circle, so that the crusts applied to titanium, zirconium and / or hafnium in step (II) are again exposed to the acid phosphating composition in step (I).
• the aluminum parts of the composite metal constructions are pre-passivated, i. they are already provided with a passivating layer containing titanium, zirconium and / or hafnium.
• the conveyor systems for the composite metal constructions have crusts which contain titanium and / or zirconium and which preferably from the phosphatization in step (I) subsequent passivation of the composite metal constructions with titanium, zirconium and / or hafnium-containing water-soluble compounds in step (II) originate.
• the conveyor systems preferably run in a circle, so that the crusts produced in step (II) are again exposed to the acid phosphating composition in step (I).
• the aluminum parts of the composite metal constructions are pre-passivated, ie they are already provided with a passivation layer containing titanium, zirconium and / or hafnium.
• the zinc phosphating composition in step (I) of the process according to the invention preferably contains at least 0.3 g / l, more preferably at least 0.8 g / l, but preferably not more than 3 g / l, more preferably not more than 2 g / l of zinc ions.
• the content of phosphate ions in the phosphating solution is preferably in the range of 5 to 50 g / l, more preferably 8 to 25 g / l, and particularly preferably 10 to 20 g / l, each calculated as P2O5.
• the zinc phosphating composition of the process according to the invention may contain, in addition to the abovementioned zinc ions and phosphate ions, additionally at least one of the following accelerators:
• Such accelerators are familiar in the prior art as components of phosphating baths and fulfill the function of "hydrogen scavengers" by directly oxidizing the hydrogen produced by the acid attack on the metallic surface and thereby reducing it itself.
• the formation of a homogeneous crystalline zinc phosphate layer is greatly facilitated by the accelerator, which prevents the formation of gaseous hydrogen on the metal surface.
• the zinc phosphating composition of the process according to the invention may contain, in addition to the abovementioned zinc ions and phosphate ions, additionally at least one of the following anions:
• the amount of up to 5 g / l, preferably up to 3 g / l of nitrate customary in nickel-containing phosphating facilitates the formation of a crystalline homogeneous and closed phosphate layer on steel as well as on galvanized and alloy-galvanized steel surfaces.
• the alkali resistance in turn plays a decisive role in a subsequent cathodic electrodeposition deposition.
• Corrosion protection and paint adhesion of the crystalline zinc phosphate layers produced with an aqueous phosphating composition according to the invention are according to experience improved if additionally one or more of the following cations is contained:
• iron (III) cations provide improved corrosion protection on steel as well as on zinc and zinc alloys.
• iron (III) cations lead to improved stability of the corresponding phosphating bath.
• the addition of iron (III) cations also makes it possible to generate a sludge flake that is easier to filter so that it is easier to remove cryolite from the bath.
• Aqueous conversion-conversion compositions which contain both manganese ions and manganese ions are known to the person skilled in the art of phosphating as trication-phosphating solutions and are also well suited for the purposes of the present invention.
• the phosphating solutions in step (I) of the process according to the invention also contain, in addition to sodium and / or potassium ions. Ions which enter the phosphating solution to adjust the free acid content.
• step (I) The flushing of water between step (I) and step (II) is obligatory since otherwise the phosphate ions contained in the phosphating composition as well as metal cations would be carried off into the passivation bath. This would lead to a difficult-to-control change in the bath parameters and to the precipitation of titanium, zirconium and / or hafnium as poorly soluble phosphates.
• the water purging process can be a water purging but also a total of at least two pours of water.
• Each water rinse can be carried out with demineralised water or city water.
• at least one surfactant may also be present.
• step (I) After working up the rinsing water enriched with the components of the phosphating bath according to step (I), a selective recycling of the components into the phosphating bath can be carried out.
• step (II) of the method by contacting the composite metal structure with the acid passivation composition according to the invention, the formation of a passive layer on the aluminum surfaces, wherein the zinc phosphate layer on the steel surfaces, galvanized and / or alloy-galvanized steel surfaces during in-contact -Ring with the passivation composition to not more than 50%, preferably not more than 20%, particularly preferably not more than 10% is dissolved.
• passivating layers of aluminum are passivating inorganic or mixed inorganic-organic thin-film coatings which do not comprise closed crystalline phosphate layers. While the pH of the acidic passivation composition ranges from 2.0 to 5.5, preferably from 2.5 to 5.5, more preferably from 3.0 to 5.5, and most preferably from 3.5 to 5, 3, essentially ensuring that no more than 50% of the zinc phosphate layer is dissolved on the steel surfaces, galvanized and / or alloy galvanized steel surfaces, the corresponding passive layers on the aluminum surfaces of the composite metal construction are typically produced by chromium-free acid passivation compositions.
• the passivating composition contains at least one water-soluble compound selected from the water-soluble compounds of the metal ions of Mo, Cu, Ag, Au, Ti, Zr, Hf, Pd, Sn, Sb, Li, V and Ce.
• the water-soluble compounds are in each case present in a concentration in the following preferred, particularly preferred and very particularly preferred ranges (in each case calculated as the corresponding metal):
• the metal ions contained in the water-soluble compounds are deposited either in the form of a salt which preferably contains the corresponding metal cation (eg molybdenum or tin) in at least two oxidation states - in particular in the form of an oxide hydroxide, a hydroxide, a spinel or a defect spinel - or elemental on the surface to be treated (eg copper, silver, gold or palladium).
• the passivating composition contains molybdenum ions and optionally further metal ions - each in the form of water-soluble compounds.
• molybdate preferably added as molybdate, more preferably as ammonium heptamolybdate and particularly preferably as ammonium heptamolybdate x 7H 2 O of the passivation composition.
• the molybdenum ions can also be added as sodium molybdate.
• molybdenum ions can also be added to the passivation composition in the form of at least one molybdenum cation-containing salt such as molybdenum chloride, for example, and then oxidized to molybdate by a suitable oxidizing agent, for example by the accelerators described above.
• a suitable oxidizing agent for example by the accelerators described above.
• the passivation composition itself contains a corresponding oxidizing agent.
• the passivating composition contains molybdenum ions in combination with copper ions, tin ions or zirconium ions.
• a polymer or copolymer in particular selected from the group consisting of the polymer classes of polyamines, polyethyleneamines, polyanilines, polyimines, polyethyleneamines, polythiophenes and polypryrenes, and their mixtures and copolymers and polyols - lyacrylic acid.
• the content of molybdenum ions is preferably in the range from 20 to 225 mg / l, particularly preferably from 50 to 225 mg / l and very particularly preferably from 100 to 225 mg / l (calculated as Mo) and the content of zirconium ions in the range from 50 to 300 mg / l, more preferably from 50 to 150 mg / l (calculated as Zr).
• the passivation composition contains copper ions, in particular copper (II) ions and optionally other metal ions - in each case in the form of water-soluble compounds.
• the passivation composition then preferably contains a content of copper ions in the range from 100 to 500 mg / l, more preferably from 150 to 225 mg / l.
• the passivation composition contains Ti, Zr and / or Hf in complexed form, preferably in a concentration in the range from 20 to 500 mg / l, more preferably from 50 to 300 mg / l and particularly preferably from 50 to 150 mg / l (calculated as Ti, Zr and / or Hf), and optionally further metal ions in the form of water-soluble compounds. These are preferably fluoro complexes, more preferably hexafluorocomplexes.
• the passivating composition then preferably comprises 10 to 500 mg / l, more preferably 15 to 100 mg / l, and most preferably 15 to 50 mg / l of free fluoride.
• the passivating composition additionally contains at least one water-soluble compound selected from the water-soluble compounds of the metal ions of molybdenum, copper, in particular copper (II), silver, gold, palladium, tin and antimony as well as lithium, preferably of molybdenum and copper, in particular copper (II).
• the water-soluble compounds are each present in a concentration in the following preferred ranges (in each case calculated as the corresponding metal):
• the passivation composition contains, in addition to Ti, Zr and / or Hf in complexed form, in particular as fluorocomplexes, additionally at least one organosilane and / or at least one hydrolysis product thereof, ie an organosilanol, and / or at least one condensation product thereof, ie an organosiloxane / polyorganosiloxane, preferably in a concentration in the range from 5 to 200 mg / l, more preferably from 10 to 100 mg / l and particularly preferably from 20 to 80 mg / l (calculated as Si ).
• the at least one organosilane preferably has at least one amino group. It is particularly preferred that one which can be hydrolyzed to an aminopropylsilanol and / or to 2-aminoethyl-3-amino-propyl-silanol and / or a bis (trimethoxysilylpropyl) amine.
• the passivating composition additionally contains at least one water-soluble compound selected from the water-soluble compounds of the metal ions of molybdenum, copper, in particular copper (II), silver, gold, palladium, tin and antimony, and lithium, preferably of molybdenum and copper, in particular copper (II), and also at least one organosilane and / or at least one hydrolysis product thereof, ie an organosilanol, and / or at least one condensation product thereof, ie an organosiloxane / polyorganosiloxane, preferably in a concentration in the range from 5 to 200 mg / l, more preferably from 10 to 100 mg / l and particularly preferably from 20 to 80 mg / l (calculated as Si).
• the water-soluble compounds are each present in a concentration in the following preferred ranges (II), silver, gold, palladium, tin and antimony, and lithium, preferably of molybdenum and copper, in particular copper (I
• the method according to the invention for the anticorrosive treatment of composite metal structures assembled from metallic materials which at least partly also have aluminum surfaces is carried out after cleaning and activation of the metallic surfaces by first contacting the surfaces with the zinc phosphating composition of step (I), eg by spraying or dipping, at temperatures in the range of 20-65 ° C and for a time interval matched to the type of application.
• step (I) zinc phosphating composition of step (I)
• speck formation on the galvanized and / or alloy-galvanized steel surfaces is particularly pronounced in conventional immersion phosphating processes, so that the phosphating in step (I) of the process according to the invention is particularly suitable for phosphating plants which operate on the principle of the immersion process. since the speck formation in the method according to the invention is suppressed.
• step (I) It is advantageous to first clean, in particular degrease, the composite metal construction prior to treatment with the zinc-phosphating composition in step (I) in an aqueous cleaning composition.
• an acidic, neutral, alkaline or strongly alkaline cleaning composition it is possible in particular to use an acidic, neutral, alkaline or strongly alkaline cleaning composition, but optionally also an acidic or neutral pickling composition.
• An alkaline or strongly alkaline cleaning composition has proven to be particularly advantageous.
• the aqueous cleaning composition may contain, in addition to at least one surfactant, if desired, a scaffold and / or other additives such as e.g. Complexing agent included.
• a scaffold and / or other additives such as e.g. Complexing agent included.
• an activating cleaner is also possible.
• the water may optionally also contain an additive dissolved in water, such as water.
• an additive dissolved in water, such as water.
• a nitrite or surfactant may be added.
• the activation composition serves to deposit a plurality of ultrafine phosphate particles as seed crystals on the surface of the zinc and iron parts. These help in the subsequent process step, in contact with the Phosphatierzu- composition - preferably without interim flushing - form a particular crystalline phosphate layer with the highest possible number of densely arranged fine phosphate crystals or a largely closed phosphate layer on the parts of zinc and iron.
• acidic or alkaline compositions based on titanium phosphate or zinc phosphate may be considered as activating compositions.
• activating agents in particular titanium phosphate or zinc phosphate, in the cleaning composition, ie to carry out purification and activation in one step.
• the composite metal construction can be provided with a basecoat, preferably with an organic dip paint, in particular an electrodeposition paint - preferably without prior oven drying of the According to the invention treated component.
• a top coat can be applied, which may be a powder paint or a wet paint.
• the present invention also relates to a zinc phosphating composition for selectively phosphating steel, galvanized and / or alloy galvanized steel surfaces in a metallic composite construction comprising a portion of aluminum, the zinc phosphating composition having a KCI addition free acid rating of at least 0.6 points and a pH preferably in the range of 2.5 to 3.5, and
• the content of free fluoride is in the range of 10 to 200 mg / l, more preferably from 20 to 175 mg / l, more preferably from 20 to 150 mg / l, further preferably from 20 to 135 mg / l, further preferably from 20 to 120 mg / l, more preferably from 50 to 120 mg / l and most preferably from 70 to 120 mg / l.
• (S value x T) / (F tot. X [B] x 1000) is in the range from 0.13 to 22.5, preferably from 0.2 to 15 and particularly preferably from 0.4 to 10, where " T “for the temperature / ° C,” F tot. Stands for the total fluoride content / (mol / l) and ,, [B] "for the concentration of the element boron / (mol / l).
• the zinc phosphating composition according to the invention contains not more than 20 ppm, preferably not more than 15 ppm, more preferably not more than 10 ppm, more preferably not more than 5 ppm and most preferably not more than 1 ppm total of water-soluble Compounds of zirconium, titanium and / or hafnium based on the elements zirconium, titanium and / or hafnium and in particular no water-soluble compounds of zirconium, titanium and / or hafnium.
• the present invention also relates to a concentrate from which the zinc phosphating composition according to the invention can be obtained by dilution with a suitable solvent and / or dispersing medium, preferably with water, and, if appropriate, adjusting the pH.
• a suitable solvent and / or dispersing medium preferably with water, and, if appropriate, adjusting the pH.
• the dilution factor here is preferably between 2 and 100, preferably between 5 and 50.
• the present invention relates to a corrosion-protected composite metal construction which contains at least one part of aluminum and at least one part of zinc and optionally another part of iron and is obtainable by the process according to the invention.
• the composite metal structures protected against corrosion according to the method according to the invention are preferably used in the automotive supplier industry, in automotive production in body construction, in agricultural machinery, in shipbuilding, in the construction industry, and in the production of white goods.
• the present invention will become apparent from the following non-limiting exemplary embodiments and comparative examples.
• Aqueous zinc phosphating solutions were prepared, each containing a score of the free acid with KCl addition of 1.1 points, a total Fischer acid of 19.5 points, an S value of 0.056, and a pH in the range of 2.5 to 3.5.
• Said phosphatizing solutions were nickel-free and each contained 15 g / l of phosphate ions calculated as P2O5, 0.8 g / l of zinc ions, 1.0 g / l of manganese ions, varying amounts of free fluoride (see Table 1) ), 1, 0 g / l of boron in the form and calculated as BF 4 and 34 mg / l of the accelerator hydrogen peroxide.
• the phosphating solutions were brought to a temperature of 45 ° C.
• test panels made of aluminum were sprayed uniformly with in each case one phosphating solution, rinsed and immersed at room temperature for 30 s in an acidic, aqueous passivation composition which contained 150 mg / l of H 2 ZrF 6 calculated as Zr. Without previous oven drying, the sheets were still provided with an electrodeposition paint and finally with a wet paint (Standardautomobillackied).
• test panels were subjected to a 144-hour CASS test according to DIN EN ISO 9227, 2017-07 and a 1008-hour Filiform test according to DIN EN 3665, 1997-08.
• Aqueous zinc phosphating solutions (ZPL Nos. 1-8) were prepared, each having a free acid score with KCI addition of 1.5 points.
• Said phosphating solutions were nickel-free and contained in each case 15 g / l of phosphate ions calculated as P2O5, 0.8 g / l of zinc ions, 1.0 g / l of manganese ions, 100 mg / l of free fluoride and different amounts of sodium and potassium ions as well as either tetrafluoroborate or hexafluorosilicate.
• the phosphating solutions were brought to a temperature of 45 ° C and stirred in a beaker by means of stirring at medium speed.
• the dissolved concentrations of aluminum, silicon and boron were determined at the beginning (0 h) and after 24 h. As the concentration of dissolved aluminum dropped, this was due to precipitation in the form of cryolite. By contrast, the concentration of dissolved silicon decreased as a result of precipitation in the form of K2S1F6.

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