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
• • 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
  • C23C2222/10—Use of solutions containing trivalent chromium but free of hexavalent chromium

Definitions

• the invention relates to a cobalt-free aqueous passivation solution for producing conversion layers on zinc and zinc alloy layers, to a process for producing a Cr (III) -containing, cobalt-free conversion layer on a zinc or zinc alloy layer, and to the use of the passivation solution for coating Zinc or zinc alloy layers.
• the galvanic coating of components made of iron or steel with zinc or zinc alloys is carried out on a large scale and has a high economic importance.
• the deposited layers protect the base material against corrosion and thus lead to a high increase in the value of the components.
• the corrosion protection of iron or steel by zinc or zinc alloys is based on the anodic protection mechanism. Zinc or zinc alloys are less electrochemical than the base material. The corrosion attack therefore begins on the coating and the base material remains protected against corrosion as long as a closed zinc or zinc alloy surface is present.
• the applied less noble zinc or zinc alloy layers are therefore also referred to as "sacrificial layers".
• US 4,126,490 describes an aqueous, Cr (VI) -free passivation solution for forming passivation layers on zinc and zinc alloy layers.
• the passivation solution contains a chromium (III) compound, alum and vanadate.
• the corrosion resistance of the passivation layers obtained with this passivation solution is at least 24 hours in the salt spray test according to ASTM B 117-54T (identical conditions as in DIN EN ISO 9227).
• ASTM B 117-54T identical conditions as in DIN EN ISO 9227.
• WO 2010/025442 A1 discloses a composition that is substantially free of hexavalent chromium and does not contain cobalt.
• the composition comprises a dry water-soluble chromium (III) compound and a dry, vanadium-based compound which is also water-soluble.
• As the water-soluble vanadium-based compound metavanadate, pyrovanadate and orthovanadate are named.
• the user then uses the ready-to-use passivation solution with this dry mixture.
• the advantage should be that so the transport of the aqueous solutions can be avoided.
• the passivation solution is according to WO 2010/025442 preferably free of nitrates and other oxidizing agents. Refinements according to the teaching of WO 2010/025442 however, did not yield useful passivation layers as the layers were stained and wipeable after drying.
• EP 0 907 762 A1 discloses chromium (III) -containing conversion layers on zinc or zinc alloy layers which have a corrosion protection of 100-1000 hours and a layer thickness of 100-1000 nm. It is said that the corrosion protection of such a layer can be increased by the fact that the layers contain additional components from the group of silicate, cerium, aluminum and borate and additional metal compounds, in particular 1- to 6-valent metal compounds, for example compounds of Na, Al, Ag, Co, Ni, Fe, Ga, In, lanthanides, Zr, Sc, Ti, V, Mn, Cu, Zn, Y, Nb, Mo, Hf, Ta, W, as well as numerous possible anions or polymers.
• additional components from the group of silicate, cerium, aluminum and borate and additional metal compounds, in particular 1- to 6-valent metal compounds, for example compounds of Na, Al, Ag, Co, Ni, Fe, Ga, In, lanthanides, Zr, Sc, Ti, V, Mn, Cu, Zn, Y, Nb, Mo
• the object underlying the present invention is to provide a cobalt-free passivation solution with which a passivation layer can be produced on a zinc or zinc alloy layer which exhibits a resistance of more than 300 hours in the salt spray test according to DIN EN ISO 9227.
• a cobalt-free passivating solution comprising Cr (III) ions, vanadyl cations, nitrate ions, sulfate ions and one or more complexing agents for Cr (III) ions selected from the group of monocarboxylic acids, dicarboxylic acids, tricarboxylic acids , Hydroxycarboxylic acids and fluoride.
• Cr (III) ions all water-soluble Cr (III) compounds can be used.
• Cr (III) chloride CrCl 3 ⁇ H 2 O
• basic chromium sulfate CrOHSO 4, for example Chromosal BD ® from. Lanxess
• Cr (III) nitrate Cr (NO 3) 3 ⁇ 9H 2 O
• potassium chromium sulfate KCr (SO 4 ) 2 .6H 2 O.
• the Cr (III) ions are in the Passivitationsrade preferably in an amount of 0.1 - 50 g / 1, more preferably 0.5 - 5 g / l, present.
• vanadium is present in cationic form in the passivation solution, ie as a vanadyl cation.
• examples of compounds which have vanadium in cationic form and can be used in the passivation solution of the present invention are the vanadyl trihalides VCl 3 and VBr 3 , vanadyl sulfate (VOSO 4 ) and vanadyl acetylacetonate (V (acac) 2 ).
• the vanadyl cation can also be used as Diacetatokomplex.
• the diacetate complex can be prepared, for example, by first reacting vanadyl sulfate with 5 moles of sodium acetate.
• the passivating solution of the present invention contains vanadyl sulfate and / or the vanadyl diacetate complex.
• the best corrosion protection values are achieved when the weight ratio Cr / V in the passivation solution is 5/1 to 100/1. Particularly preferred is a weight ratio of Cr / V of 10/1 to 50/1. In this way, passivation layers can be produced which have a weight ratio of Cr / V of about 1/1 to 4/1 in the deposited layer.
• the passivation solution according to the present invention also contains nitrate ions.
• the amount of nitrate ions contained in the passivating solution is 0.75-75 g / l passivating solution, more preferably 2.25-40 g / l.
• the nitrate ions may be added to the passivating solution in any form.
• the nitrate ions may be added together with the Cr (III) ions as the chromium nitrate, Cr (NO 3 ) 3 .9H 2 O. It is particularly preferred to add the nitrate ions as sodium nitrate. It is also possible to combine different nitrate sources, for example, by the addition of chromium (III) nitrate, which is then simultaneously source of the Cr (III) ions, and sodium nitrate.
• the passivating solution according to this invention contains sulfate ions.
• the preferred sulfation concentration is in the range of 0.07 to 50 g / L, more preferably 0.35 to 10 g / L. It has been found to be particularly advantageous to select the sulfate concentration such that it is present in the passivating solution in half the molar amount based on Cr (III).
• source of sulfate ions all water-soluble sulfate salts can be used, provided that the counterion does not adversely affect the formation of the passivation layer.
• sodium sulfate is used.
• the sulfate ions may also be added together with the vanadyl cation as vanadyl sulfate and / or together with the chromium (III) ions as the chromium sulfate.
• the passivation solution of the present invention further contains one or more complexing agents capable of complexing Cr (III) ions.
• the complex image is selected from the group consisting of monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, hydroxycarboxylic acids and fluoride.
• a typical representative of a monocarboxylic acid is acetic acid.
• dicarboxylic acids which can be used in the passivation solution of the present application are oxalic acid, malonic acid and succinic acid.
• the tricarboxylic acid there may be mentioned, for example, citric acid and, as the hydroxy acid, the malic acid, glycolic acid and tartaric acid.
• hydroxycarboxylic acids are aromatic hydroxy or polyhydroxycarboxylic acids such as salicylic acid or gallic acid.
• the carboxylic acid can be added as a salt, for example sodium or potassium salt, or as the free acid.
• fluoride As fluoride ions, all soluble fluoride compounds can be used.
• Preferably used are sodium fluoride, NaF, potassium fluoride, KF, ammonium fluoride, NH 4 F, sodium bifluoride, NaF ⁇ HF, potassium bifluoride, KF ⁇ HF, ammonium bifluoride, NH 4 F ⁇ HF.
• sodium fluoride, NaF is particularly preferable.
• the molar ratio to Cr (III) ions be 2/1, so that at least two coordination sites of the chromium atom can be occupied.
• more-functional complexing agents as in the case of the di- and tricarboxylic acids, it is likewise preferable for these to be present in a doubly molar ratio to chromium, based on the functional groups of the complexing agent.
• the preferred maximum amount of complexing agent is achieved when the Cr (III) complex is fully coordinated with complexing ligands.
• the preferred maximum amount is the 6-fold molar amount based on Cr (III) and in the case of eg bidentate ligands (eg malonic acid) the 3-fold molar amount based on Cr (III) ,
• sodium fluoride when sodium fluoride is used as a complexing agent, it is preferable to use an amount of 0.1 to 50 g / l, more preferably 0.5 to 10 g / l.
• the sulfate ion concentration is selected to be in one-half molar amount based on Cr (III).
• the present invention further provides a process for producing a Cr (III) -containing conversion layer on Zn or Zn alloy layers.
• the conversion layer is formed by dipping the Zn or Zn alloy layer in the passivation solution of the present invention.
• the immersion time is in the range of 30 to 120 seconds.
• the passivation solution preferably has a temperature of 15 ° C to 60 ° C. In this way, conversion layers can be produced which have a thickness of about 20 to 500 nm. The longer the immersion time and the higher the temperature of the passivation solution, the thicker the layers obtained become.
• the conversion layers obtained are Cr (VI) -free. After immersing the Zn or Zn alloy layers in the passivation solution, the samples are taken, then usually rinsed with water and then dried, preferably at elevated temperature (eg 80 ° C, 20 minutes).
• the layers obtained have a thickness of less than 100 nm, in particular of about 50-70 nm, and even at these low layer thicknesses, a resistance in the salt spray test according to DIN EN ISO 9227 of more than 300 hours can be achieved.
• a layer can be obtained, for example, under the process conditions described in Example 1.
• the passivation concentrate is ready for use.
• 25 ml of the passivation concentrate described above are made up to 1000 ml with water and the pH is adjusted to 1.9 with nitric acid.
• a weakly acidic commercial zinc bath (zinc bath Slotanit OT 1, Dr.-Ing Max Schlötter) steel sheets are coated with about 10 ⁇ m zinc.
• These Test panels are passivated at 25 ° C for 60 seconds in the passivation solution.
• the treated panels were then rinsed with deionized water and dried in a convection oven at 80 ° C for 20 minutes. This results in slightly violet-blue iridescent passive layers.
• Passivation solution made up to 1000 ml and the pH adjusted to 1.9 with nitric acid.
• a weak Acid commercially available zinc bath (zinc bath Slotanit OT 1, Dr.-Ing Max Schlötter) steel sheets are coated with about 10 microns of zinc.
• These test panels are passivated at 25 ° C for a period of 120 seconds in the passivation solution.
• the treated panels were then rinsed with deionized water and dried in a convection oven at 80 ° C for 20 minutes. This results in yellow-violet, greenish iridescent passive layers.
• the passivation concentrate is ready for use.
• 35 ml of the passivation concentrate described above are made up to 1000 ml with water and the pH is adjusted to 1.9 with nitric acid.
• a weakly acidic commercial zinc bath (zinc bath Slotanit OT 1, Dr.-Ing Max Schlötter) steel sheets are coated with about 10 ⁇ m zinc. These test sheets are baked at 25 ° C for 60 seconds the passivation solution passivated.
• the treated panels were then rinsed with deionized water and dried in a convection oven at 80 ° C for 20 minutes. This results in slightly violet-blue iridescent passive layers.
• the passivation concentrate is ready for use.
• 35 ml of the passivation concentrate described above are made up to 1000 ml with water and the pH is adjusted to 1.9 with nitric acid.
• a weakly acidic commercial zinc bath (zinc bath Slotanit OT 1, Dr.-Ing Max Schlötter) steel sheets are coated with about 10 ⁇ m zinc.
• These test panels are passivated at 25 ° C for 60 seconds in the passivation solution. The treated panels were then rinsed with deionized water and dried in a convection oven at 80 ° C for 20 minutes.
• Comparative Example 2 and Comparative Example 1 show that addition of cobalt sulfate to the passivation concentrate can improve the corrosion resistance of the passivation layer.
• the replacement of cobalt sulfate by the vanadium compound according to the invention again causes a substantial increase in the corrosion protection.
• Example 1 Test No. 21 was made US 4,126,490 reworked.
• the pH of the passivation solution was 1.8.
• test panels were passivated at 25 ° C for a period of 10 seconds in the passivation solution. The treated panels were then rinsed with deionized water and dried in a convection oven at 80 ° C for 20 minutes. Passivation layers with blue-violet irrigation were obtained.
• Comparative Example 4 was a passivation solution according to the information in WO 2010/025442 A1 reworked.
• passivating concentrates according to the invention having the same chromium salt concentration but different vanadium salt concentrations were used.
• Passivation solutions each containing 35 ml / l of the passivation concentrate were prepared from these concentrates and passivated freshly galvanized copper sheets (surface 1 dm 2 ) at 25.degree. C. for 60 seconds each.
• the passivation layer of one test sheet was then removed by immersion in 16% strength by weight hydrochloric acid. This solution was dissolved in a 100 ml volumetric flask and therein the elements chromium and vanadium were determined by ICP analysis and thus the relative Proportions of chromium and vanadium in the passivation layer determined.
• This concentrate contains 1.0 g / kg vanadium and 21.2 g / kg chromium.
• This concentrate contains 1.56 g / kg vanadium and 21.2 g / kg chromium.
• This concentrate contains 3.2 g / kg vanadium and 21.2 g / kg chromium.
• This concentrate contains 4.08 g / kg vanadium and 21.2 g / kg chromium.
• This concentrate contains 4.8 g / kg vanadium and 21.2 g / kg chromium.
• a passivation test was carried out with the concentrate from experiment 3c with a batch concentration of 200 ml / l.
• the passivation solution contained 5.6 g / l of chromium and 412 mg / l of vanadium and thus, based on the chromium content, corresponds to a passivation solution of the type used in the cobalt-containing passivations.
• Galvanized sheets were passivated at pH 1.9 and 25 ° C for 120 seconds. A yellowish-green passivation layer was obtained.

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• 2011
  • 2011-02-24 EP EP11155782A patent/EP2492371A1/fr not_active Withdrawn

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