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
  • C23C22/48—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 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
  • C23C22/53—Treatment of zinc or alloys based thereon

Definitions

• chromium (VI) is reduced to chromium ( I I I ) which is precipitated as, inter alia, chromium ( I I I ) hydroxide or a sparingly soluble ⁇ - ⁇ - or ⁇ -hydroxo-bridged chromium ( I I I ) complex in the, inter alia, surface film which is more alkaline as a result of the evolution of hydrogen. Sparingly soluble zinc chromate(VI) is formed in parallel. Overall, a closed, impermeable conversion layer which protects very effectively against corrosive attack by electrolytes is formed on the zinc surface. Chromium (VI) compounds have not only an acute toxicity but a high carcinogenic potential, so that a replacement for the processes associated with these compounds is necessary.
• Dyes as are also used in Cr ( 111 ) -based passivations can in principle also be used in the case of chromium-free conversion layers.
• a transition metal such as cobalt or iron is generally added as Co (II) or Fe(II) or Fe(III) to the passivation in order to produce finely divided, black pigments in situ in the conversion layer.
• Treatment solutions for producing such black passivations are described, for example, in EP 1 970 470 Al .
• Such treatment solutions comprise nitrate ions and at least two different carboxylic acids in addition to Cr 3+ and Co 2+ ions.
• Iron has the disadvantage that the corrosion protection of the system is significantly weakened by incorporation of iron-containing pigments. Although cobalt allows systems having a better corrosion protection, it has the disadvantage of being not unproblematical from a health point of view under particular conditions.
• the patent text JP 2005-206872 describes a Cr 6+ ion-free treatment solution for producing black passivations, which solution contains Cr 3+ ions together with at least one further ion selected from the group consisting of sulphate, chloride, ions of the oxo acids of chlorine and nitrate and also a sulphur compound.
• the black conversion layers produced in this way contain chromium ions .
• the document JP 2005-187925 describes treatment solutions for producing coloured passivation layers containing Cr 3+ ions, further metal ions and an organic sulphur compound.
• the black conversion layers produced in this way contain chromium ions.
• the document JP 2005-187838 likewise describes aqueous treatment solutions for producing black passivation layers, which solutions contain ions selected from at least Ni and Co and also a sulphur compound.
• the black conversion layers produced in this way contain nickel and/or cobalt ions.
• a process which combines the ecological and occupational hygiene advantage of a chromium- and cobalt-free passivation with a decoratively high- quality black colour impression is therefore desirable.
• the invention is based on the use of sulphur-containing compounds in an aqueous, acidic matrix which is free of chromium ions and cobalt ions.
• Such treatment solutions enable black conversion layers to be produced on zinc and alloys thereof.
• the treatment solutions of the invention contain a) at least one complex, water-soluble metal cation selected from the group consisting of oxo cations of the formula M' 0, d+
• M"X a ⁇ where X is selected from the group consisting of F, CI, Br and I, a is an integer from 3 to 6, b is an integer from 1 to 4 and M' and M" are selected from the group consisting of Mn, V, Ti, W, Mo, Zr, B, Si and Al; b) at least one oxidant selected from the group consisting of hydrogen peroxide, organic peroxides, alkali metal peroxides, perborates, persulphates , nitrates, organic nitro compounds, organic N-oxides and mixtures thereof; at least one organic sulphur compound selected from the group consisting of compounds of the formulae (1) and (2)
• R 5 OOC-R 3 -S-S-R 4 -COOR 6 (2), where R 1 is selected from among Cl-C8-alkyl, linear and branched, aryl, with preference being given to Cl-C2-alkyl ;
• R 2 is selected from among H, a suitable cation (NH 4 + , Li + , Na + , K + ) and Cl-C4-alkyl, linear and branched;
• R 3 and R 4 are selected independently from among
• R 5 and R 6 ' are selected independently from among H, a suitable cation (NH 4 + , Li + , Na + , K + ) and Cl-C4-alkyl, linear and branched, with the radicals R 5 and R 6 preferably being identical.
• Suitable sulphur compounds of the formulae (1) and (2) enables a black coloration of the conversion layer to be achieved even in the absence of chromium, iron, cobalt and nickel.
• the list of compounds of this type is not exhaustive and includes, in particular, compounds which can liberate suitable compounds corresponding to the above formulae by hydrolysis or the like under the conditions of the solutions to be used for making up the reaction solution or under the conditions of the reaction solution or the reaction with the metal surface, for example the salts and esters of these compounds.
• the most preferred sulphur compounds are thioglycolic acid, 3-thiopropionic acid, dithiodiglycolic acid and thiolactic acid.
• the sulphur compounds of the formulae (1) and (2) are added in an amount of from 0.2 g/1 to 500 g/1, preferably from 1 g/1 to 100 g/1 and most preferably from 3 g/1 to 20 g/1, to the treatment solution of the invention .
• the oxo cations of the formula M' O c d+ are preferably added in the from of their nitrates, sulphates and halides, from which the oxo cations are formed by hydrolysis in the treatment solution, to the treatment solution of the invention.
• zirconyl sulphate ZrO(S0 4 )
• ZrO(S0 4 ) zirconyl sulphate
• suitable metals M' are Mn, V, W, Mo, Ti and Zr.
• suitable oxo cations are MnO + , V0 3+ , V0 2+ , W0 2 2+ , Mo0 2 2+ , Ti0 2+ , Zr0 2+ and mixtures thereof.
• Particularly preferred oxo cations are those of titanium and of zirconium.
• the oxo cations are added in an amount of from 0.02 g/1 to 50 g/1, preferably from 0.05 g/1 to 10 g/1 and most preferably from 0.1 g/1 to 5 g/1, to the treatment solution.
• the complex halogen ions of the formula M"X a b ⁇ are added in the form of their metal salts, preferably their alkali metal salts, particularly preferably their sodium and potassium salts.
• Particular preference is given to the complex halogen ions SiF 6 2 ⁇ , TiF6 2 ⁇ and ZrF6 2 ⁇ .
• the complex halogen anions of the formula M"X a b ⁇ are added in an amount of from 0.02 g/1 to 100 g/1, preferably from 0.05 g/1 to 50 g/1 and most preferably from 0.1 g/1 to 10 g/1, to the treatment solution of the invention.
• the treatment solution of the invention can contain either at least one oxo cation of the formula M' O c d+ where M' is Mn, V, Ti, W, Mo, Zr or at least one complex halogen ion of the formula M"X a b ⁇ .
• the treatment solution contains a mixture of both at least one oxo cation and at least one complex halogen ion. This embodiment is preferred since it results in increased corrosion resistance of the metal layer (cf . Examples 3 to 7) .
• the at least one oxidant in the treatment solution of the invention is selected from the group consisting of hydrogen peroxide, organic peroxides, alkali metal peroxides, persulphates , perborates, nitrates and mixtures thereof.
• the most preferred oxidant is hydrogen peroxide.
• the at least one oxidant is added in an amount of from 0.2 g/1 to 100 g/1, preferably from 1 g/1 to 50 g/1 and most preferably from 5 g/1 to 30 g/1, to the treatment solution.
• the pH is adjusted by means of an acid or base to a value in the range from 0.5 to 5.0, preferably in the range from 1.0 to 3.0, particularly preferably in the range from 1.3 to 2.0.
• HNO 3 or H 2 SO 4 is preferably used as acid, and sodium hydroxide is preferably used as base.
• the treatment solution of the invention is used for producing corrosion protection layers by direct treatment of the metal surfaces with the treatment solution, by dipping the substrate to be coated into the treatment solution or flushing the substrate with the treatment solution.
• the use by dipping or flushing is preferably carried out at a temperature of the treatment solution in the range from 20 to 100°C, preferably from 30 to 70°C, more preferably from 40 to 60°C and particularly preferably at about 50°C.
• the most suitable treatment time for producing corrosion protection layers by dipping or flushing of the substrate to be coated into or with the treatment solution varies as a function of various parameters, e.g. the composition of the treatment solution, the treatment temperature, the type of metal surface and the degree of desired corrosion protection, and can be determined by means of routine experiments. In general, the treatment time is in the range from 5 to 180 s, preferably in the range from 30 to 120 s.
• the black conversion layers deposited in this way produce good corrosion protection based on the formation of zinc corrosion products on zinc-containing surfaces .
• the conversion layers described can be subjected to conventional after-treatment processes. These include, for example, sealing by means of silicates, organofunctional silanes and nanosize S1O 2 and also polymer dispersions.
• the sealing layers produced by the subsequent treatment improve the barrier action of the underlying conversion layer and thus additionally improve the corrosion protection afforded by the overall coating system.
• the pH is adjusted to pH 1.6 at 50°C by means of NaOH.
• a sheet of low-alloy steel is, after suitable pretreatment , coated with 10 ym of zinc in an alkaline zinc-plating electrolyte (Protolux® 3000, a product of Atotech GmbH, containing 12 g/1 of zinc and 120 g/1 of NaOH) .
• the metal sheet After zinc-plating, the metal sheet is rinsed and dipped directly into the treatment solution prepared above. After a treatment time of 60 s with gentle agitation, the metal sheet is taken out, rinsed and dried. It has a multicoloured iridescent surface.
• a treatment solution as described in Comparative Example 1 for producing conversion layers is admixed with 10 g/1 of thioglycolic acid and the pH is adjusted to pH 1.6 (50°C) by means of NaOH.
• a sheet of low-alloy steel is, after suitable pretreatment, coated with 8-15 ym of zinc in an alkaline zinc-plating electrolyte (Protolux® 3000, a product of Atotech Deutschland GmbH, containing 12 g/1 of zinc and 120 g/1 of NaOH) .
• an alkaline zinc-plating electrolyte Protolux® 3000, a product of Atotech GmbH, containing 12 g/1 of zinc and 120 g/1 of NaOH
• a treatment solution as described in Comparative Example 1 for producing conversion layers is admixed with 11 g/1 of 3-thiopropionic acid and the pH is adjusted to pH 1.6 (50°C) by means of NaOH.
• a sheet of low-alloy steel is, after suitable pretreatment , coated with 10 ym of zinc in an alkaline zinc-plating electrolyte (Protolux® 3000).
• the metal sheet After zinc-plating, the metal sheet is rinsed and dipped directly into the treatment solution prepared above. After a treatment time of 60 s with gentle agitation, the metal sheet is taken out, rinsed and dried. It has a deep-black surface.
• a treatment solution as described in Comparative Example 1 for producing conversion layers is admixed with 11 g/1 of dithiodiglycolic acid and the pH is adjusted to pH 1.6 (50°C) by means of NaOH.
• a sheet of low-alloy steel is, after suitable pretreatment, coated with 10 ym of zinc in an alkaline zinc-plating electrolyte (Protolux® 3000). After zinc-plating, the metal sheet is rinsed and dipped directly into the treatment solution prepared above. After a treatment time of 60 s with gentle agitation, the metal sheet is taken out, rinsed and dried. It has a deep-black surface.
• the metal sheet with the surface produced in this way is dried at 80°C in a convection oven for 15 min and the corrosion protection is tested in the neutral salt spray mist test in accordance with ISO 9227 NSS.
• a metal sheet having a surface produced according to Example 3 is rinsed, dipped into a sealing solution comprising a silicate-containing polyurethane dispersion (Corrosil® Plus 501, a product of Atotech GmbH) and dried at 80 °C in a convection oven for 15 min.
• the corrosion protection was tested in the neutral salt spray mist test in accordance with ISO 9227 NSS.
• a sealing solution customarily used for increasing corrosion protection can thus also be used on the chromium- and cobalt-free black conversion layers according to the invention.
• Example 1 for producing conversion layers is admixed with 13 g/1 of thiolactic acid and the pH is adjusted to pH 1.6 (50°C) by means of NaOH.
• a sheet of low-alloy steel is, after suitable pretreatment , coated with 10 ym of zinc in an alkaline zinc-plating electrolyte (Protolux® 3000).
• the metal sheet After zinc-plating, the metal sheet is rinsed and dipped directly into the treatment solution prepared above. After a treatment time of 60 s with gentle agitation, the metal sheet is taken out, rinsed and dried. It has a deep-black surface.
• the metal sheet with the surface produced in this way is dried at 80°C in a convection oven for 15 min and the corrosion protection is tested in the neutral salt spray mist test in accordance with ISO 9227 NSS.
• the pH is adjusted to pH 1.6 at 50°C by means of HNO 3 .
• a sheet of low-alloy steel is, after suitable pretreatment , coated with 10 ym of zinc in an alkaline zinc-plating electrolyte (Protolux® 3000).
• the metal sheet After zinc-plating, the metal sheet is rinsed and dipped directly into the treatment solution prepared above. After a treatment time of 60 s with gentle agitation, the metal sheet is taken out, rinsed and dried. It has a deep-black surface.
• the metal sheet with the surface produced in this way is dried at 80°C in a convection oven for 15 min and the corrosion protection is tested in the neutral salt spray mist test in accordance with ISO 9227 NSS.
• the pH is adjusted to pH 1.6 at 50°C by means of NaOH.
• a sheet of low-alloy steel is, after suitable pretreatment , coated with 10 ym of zinc in an alkaline zinc-plating electrolyte (Protolux® 3000). After zinc-plating, the metal sheet is rinsed and dipped directly into the treatment solution prepared above. After a treatment time of 60 s with gentle agitation, the metal sheet is taken out, rinsed and dried. It has a deep-black surface.
• the metal sheet with the surface produced in this way is dried at 80°C in a convection oven for 15 min and the corrosion protection is tested in the neutral salt spray mist test in accordance with ISO 9227 NSS.

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• 2009
  • 2009-09-23 ES ES09171140T patent/ES2372146T3/es active Active
  • 2009-09-23 AT AT09171140T patent/ATE525495T1/de active
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• 2010
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