Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/24—Chemical after-treatment
  • C25D11/246—Chemical after-treatment for sealing layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/24—Chemical after-treatment
  • C25D11/243—Chemical after-treatment using organic dyestuffs

Definitions

• the invention relates to agents and a method for producing colorless, compacted layers on anodized aluminum surfaces in the course of the so-called "cold compression".
• the technology In contrast to the so-called “hot compression", in which the pores of anodized aluminum surfaces are closed by treatment with water, water vapor or metal salt solutions above 90 ° C and aluminum surfaces are thereby made corrosion-resistant and resistant to other external influences, the technology generally means the so-called “Cold compaction” or “cold impregnation” or “low-temperature compaction” processes with which the porosity of anodized aluminum surfaces is reduced and the surface properties are significantly improved at temperatures in the range between 15 and 70 ° C. The main goal is improved corrosion protection compared to an undensified surface.
• DE-OS 33 01 507 also describes a method for cold compressing workpieces made of aluminum and its alloys, in which fluorine or surface treatment at temperatures around 25 ° C.
• Solutions containing fluoride including solutions containing nickel fluoride and / or cobalt fluoride can also be used.
• DE-OS 34 11 678 discloses a process for the post-compression of aluminum and aluminum alloys following the anodization, in which aqueous solutions of at least one nickel salt are added nonionic surfactants which are capable of lowering the surface tension of the compression bath.
• Organosilicon compounds are preferably used for this purpose.
• All of the described processes have in common that aqueous solutions of certain nickel salts are used.
• the nickel ions are incorporated into the surface layer when they come into contact with the freshly anodized aluminum surfaces, whereby - depending on the anions that are also incorporated - there is a more or less strong greenish discolouration of the aluminum surfaces, particularly when viewed from an angle or at an acute angle becomes visible.
• the greenish surface discoloration is very annoying because it changes the actual natural tone of the aluminum metal.
• Monoazo dyes are mainly used in the aluminum industry to consciously color anodized aluminum surfaces.
• the dyes penetrate into the porous surfaces of anodized aluminum parts under adsorption, after which the colored layers are usually compacted by treatment in hot aqueous solutions.
• substances are added to the compression solutions that prevent the formation of sealing coatings (see: Aluminum 47, 245 (1971)).
• nickel salts for example nickel acetate
• the invention is therefore based on the object of providing a method for cold compression of anodized aluminum surfaces in which colorless layers can be produced despite the use of aqueous solutions containing nickel salt, and the greenish ones Discoloration due to nickel ions in the surface layers can be avoided.
• Aqueous solutions of nickel fluoride absorb light in the wavelength ranges 350 to 450 nm and 650 to 850 nm.
• the invention relates to agents for producing colorless sealing layers of anodized aluminum surfaces at temperatures in the range from 15 to 70 ° C. and pH values in the range from 5 to 7.5, which contain 1 to 5 g of nickel per liter of sealing solution in the form of a water-soluble nickel salt several organic dyes, which have an absorption maximum in the range from 450 to 600 nm, have an extinction coefficient of at least 1. 10 3 l.mol -1 .cm -1 , can be dissolved in a molecular dispersion and with nickel ions and / or the other constituents of the solution no precipitation reactions occur at application concentrations and, if appropriate, contain further organic and / or inorganic auxiliaries customary in cold compression anodized aluminum surfaces.
• the invention also relates to a process for producing colorless compaction layers by treating anodized aluminum surfaces with nickel ions and optionally further aqueous solutions containing organic and / or inorganic auxiliaries customary in cold compaction of anodized aluminum surfaces at temperatures in the range from 15 to 70 ° C. and pH values in Range from 5 to 7.5, which is characterized in that, optionally continuously, one or more organic dyes are added to the compression solutions, which have an absorption maximum in the range from 450 to 600 nm, an extinction coefficient of at least 1.10 l .mol -1 .cm -1 , can be dissolved in a molecular dispersion and no precipitation reactions occur with nickel ions and / or the other components of the solution at application concentrations.
• azo or azo metal dyes proved to be suitable for fulfilling all of the criteria (a) to (d) mentioned. From the large group of azo or azo metal dyes, however, those are not suitable that either cannot diffuse into the pores of the aluminum oxide hydrate surface due to their molecular size or result in the precipitation with the nickel ions of the compression solutions.
• the use of the azo and azo metal dyes suitable according to the invention means that, for a given nickel concentration of, for example, 1 to 5 g of nickel / 1 on the one hand and concentrations of dye molecules of, for example, 1 to 10 mg of dye / 1 on the other hand, within a treatment time of 0.1 to 1 , 5 min per micron layer thickness, the nickel ions and dye molecules are incorporated into the aluminum oxide hydrate layer in such a ratio that an absorption of the light energy of the entire visible spectrum is the result.
• Azo dyes which are sold by the company SANDOZ under the names Aluminum Red GLW or Aluminum Violet CLW were preferably used in the context of the present invention.
• Aluminum red GLW is an azo metal complex with copper and bie aluminum violet CLW is a purely organic azo dye.
• the dyes mentioned At high color intensity (extinction coefficient about 1. 10 4 l. Mo l 1 .cm -1 ), the dyes mentioned have an absorption maximum at 500 or 555 nm and, due to their molecular size (molecular weight approx. 800 to 1000), diffuse easily into the pores of the anodized aluminum surfaces.
• Using these dyes have proven to be expedient in the compression process at nickel concentrations in the range of about 2 g nickel / l dye concentrations of a total of about 2.5 mg dye / 1, the treatment solution containing all components appearing colorless.
• Aqueous solutions of nickel salts which are prepared by dissolving in particular NiF 2 4 H 2 O or other nickel salts such as nickel sulfate or nickel acetate, and adding appropriate amounts of alkali metal fluorides, are used for the compression.
• the compression solutions according to the invention can optionally contain further organic and / or inorganic auxiliaries customary in cold compression anodized aluminum surfaces.
• Surfactants and / or organic compounds such as alcohols, amines, ketones and / or ethers and / or organosilicon compounds and / or fluorides of different metals and / or salts with complex anions are suitable as such.
• these solutions are not essential and the anodized aluminum surfaces are colorlessly compacted even in the absence of such customary auxiliaries.
• anodized surfaces made of aluminum or its alloys primarily with an aqueous solution of the dyes which can be used according to the invention and then to compact them with an aqueous nickel salt solution using the cold method.
• the reddish coloration of the aluminum oxide surface obtained in the first process step compensates for the subsequent greenish coloration resulting from the sealing process, so that aluminum oxide surfaces are formed with the natural color of the aluminum.
• a dye rinse bath must always be included operate over a water overflow, which makes it difficult to maintain a certain dye concentration and results in large dye losses.
• anodizing lines that are commonly used for the fully automatic treatment of surfaces made of aluminum and its alloys have no space for the installation of a separate pre-dye bath.
• aqueous solutions which contain 1 to 5 g of nickel per liter of compression solution in the form of a water-soluble nickel salt, 0.5 to 80 mg per liter of compression solution of one or more organic dyes, which must meet the above-mentioned criteria (a) to (d) and, if appropriate, contain further organic and / or inorganic auxiliaries customary in the cold compression of anodized aluminum surfaces.
• the solutions preferably have a dye content of 1 to 10 mg, particularly preferably 1 to 2.9 mg of dye per liter of compression solution, this amount of dye being dependent on the one hand on the nickel concentration and on the other hand on the color intensity of the dye used.
• treatment solutions are used in which the coloring of the nickel ions is compensated for by the red coloring caused by the dye molecules and which thus appear colorless.
• Dyes with an extinction coefficient in the range from 5,103 to 5 . 10 5 l.ml -1 .cm -1 with a A b-absorption maximum in the range of 490 to 560 nm discolor in a concentration of 1 to 10 mg / 1 compression solutions containing 1 to 5 g / 1 of nickel.
• anodized surfaces made of aluminum or its alloys are treated with such dye solutions. This takes place in that the corresponding aluminum parts for a time of 0.1 to 1.5 min / ⁇ m layer thickness, preferably for a time of 0.4 to 1.2 min / ⁇ m layer thickness, into which the components according to the invention ent solutions are immersed. It is then conveniently rinsed with demineralized water.
• the compression solutions are re-sharpened in accordance with the consumption of their components, so that a continuous process control is possible.
• both the nickel content and the dye content are set to a constant value and the exact observance of these and the other bath parameters is continuously monitored.
• sheets of the alloy AlMg 3 (DIN material No. 3.3535) were degreased, rinsed, pickled, rinsed and anodized in the GS process in compliance with the following process parameters:
• aqueous solutions were used which had the composition mentioned in the individual examples.
• the pH was between 5.5 and 6.5 and was corrected with acetic acid if necessary.
• the treatment temperature was 28 to 32 ° C, the treatment time was 0.5 min / ⁇ m layer thickness.
• the nickel content of the solutions was monitored by complexometric titration.
• the solution was photometrized in cuvettes with a layer thickness of 1 cm in a spectrophotometer.
• the extinctions (cm -1 ) at the characteristic absorption wavelength (Ni: 395 and 720 nm; dyes: 500 and 555 nm) are directly dependent on the respective concentration and can therefore be correlated.
• the starting solution contained 7.0 g of NiF 2 . 4H 2 0 per liter of compression solution and 3.0 mg aluminum violet CLW per liter of compression solution.
• the pH was 5.8.
• Nickel ions and dye were thus simultaneously embedded in the pores of the aluminum oxide hydrate layer.
• the starting solution contained 7.0 g of NiF 2 . 4 H 2 0 per liter of compression solution and 5.0 mg aluminum copper per liter of compression solution.
• the pH was 5.8.
• the starting solution contained 7.0 g of NiF 2 . 4 H 2 0 and 5.0 mg aluminum red GLW per liter of compression solution.
• the pH was 5.8.
• the starting solution contained 5.5 g of NiF 2 . 4 H 2 0 per liter compression solution, 1.0 mg aluminum red GLW per liter compression solution and 2 mg aluminum violet CLW per liter compression solution.
• the starting solution contained 5.5 g of NiF 2 . 4 H 2 0 per liter compression solution, 1.25 mg aluminum red GLW and 1.25 mg aluminum violet CLW per liter compression solution.
• nickel ions By adding the supplementary solution, the content of nickel ions was kept almost constant, while the dye concentration was still subject to wide fluctuations. However, nickel and dyes were incorporated into the pores of the aluminum oxide hydrate surfaces and consequently colorless surfaces with a natural metallic luster were obtained.
• the starting solution contained 5.7 g of NiF 2 . 4 H 2 0, 1.25 mg aluminum red GLW and 1.25 mg aluminum violet CLW per liter of compression solution.
• a supplementary solution was metered in, which contained 40.2 g of nickel per liter of compression solution and 26.8 mg of the dyes mentioned in Example 4 per liter of compression solution.
• the nickel ion and dye content could be adjusted to almost constant values.
• the present supplementary solution proved to be the most suitable for the given experimental setup.
• the starting solution contained 5.7 g of NiF 2 . 4 H 2 0, 1.25 mg aluminum red GLW and 1.25 mg aluminum violet CLW per liter of compression solution.
• the supplementary solution contained 30 g of nickel 18.75 mg of the two dyes mentioned per liter of compression solution.
• the content of nickel ions and dye molecules could be kept almost constant by resharpening the compaction solution with the supplementary solutions mentioned. To the extent necessary, both coloring components were built into the pores of the aluminum oxide hydrate surface. This resulted in undyed layers with a natural metallic sheen.
• a cold impregnation solution containing 2 g / 1 nickel and 1.4 g / 1 fluoride was prepared in an 18 m 3 bath container. 1.25 mg / 1 aluminum red GLW and 1.25 mg / l aluminum violet CLW were added so that the solution appeared colorless on visual assessment. Over a first test period of 8 weeks, a total of 11,500 m 2 of anodized aluminum parts with layer thicknesses of the oxide layer between 2 and 25 ⁇ m and different anodization conditions were treated in this bath.
• the nickel content was determined by complexometric titration. The dye content was checked photometrically. If necessary to maintain the nickel concentration at 2 g / 1, a nickel salt solution which also contained the above-mentioned dyes was added. This solution contained nickel and dye (50% aluminum red GLW and 50% aluminum violet) in a weight ratio of 1: 0.0015. The total consumption was 12.3 kg Ni and 18 g dye mixture. All parts treated in this way could be impregnated in this bath colorless, ie without greenish discoloration. The The solution also remained colorless when viewed visually.

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• Chemical Treatment Of Metals (AREA)
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• Application Of Or Painting With Fluid Materials (AREA)
• Sealing Material Composition (AREA)
• Paints Or Removers (AREA)
• Laminated Bodies (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

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• 1985
  • 1985-01-03 DE DE19853500079 patent/DE3500079A1/de not_active Withdrawn
  • 1985-12-23 CA CA000498514A patent/CA1268604A/fr not_active Expired - Fee Related
  • 1985-12-23 DE DE8585116510T patent/DE3568800D1/de not_active Expired
  • 1985-12-23 AT AT85116510T patent/ATE41448T1/de not_active IP Right Cessation
  • 1985-12-23 EP EP85116510A patent/EP0186897B1/fr not_active Expired
  • 1985-12-27 JP JP60299735A patent/JPS61159597A/ja active Granted
• 1986
  • 1986-01-02 AU AU51793/86A patent/AU573065B2/en not_active Ceased
  • 1986-01-02 ZA ZA8618A patent/ZA8618B/xx unknown
• 1987
  • 1987-04-14 US US07/038,480 patent/US4756771A/en not_active Expired - Lifetime

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