Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/04—Electroplating: Baths therefor from solutions of chromium
  • C25D3/10—Electroplating: Baths therefor from solutions of chromium characterised by the organic bath constituents used
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K13/00—Etching, surface-brightening or pickling compositions
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/04—Electroplating: Baths therefor from solutions of chromium
  • C25D3/08—Deposition of black chromium, e.g. hexavalent chromium, CrVI

Definitions

• the present invention relates to the field of additives for chromium electrolytes, especially to the field of the additive surfactants for chromium electrolytes, and to the field of the additives for chromic acid solutions applied for polymer metallizations.
• foam-forming wetting agents foam-forming wetting agents
• surfactants foam-forming wetting agents
• PFOAs perfluoroalkylsulphonic acids
• These products are also stable to the highly oxidative properties of chromic acid.
• fluorine surfactants are not biodegradable, since they do not undergo any photolytic, hydrolytic, oxidative or reductive transformation whatsoever. They are biodegraded neither aerobically nor anaerobically. Owing to their physicochemical properties, perfluoroalkylsulphonic acids remain as end metabolites and are not degraded any further.
• DE-B 1 034 945 has proposed already up to 10 g/l alkylmethylsulphonates (i.e. salts of bis or monoalkylmethan sulfonic acid) as additives, which are said to have the properties of a surfactant and simultaneously bring about process-improving influences with regard to the smoothing of the chromium layer.
• these additives are unsuitable in practice, since they decompose in the course of chromium-plating within a very short time.
• DE-C 39 33 896 describes the addition of saturated aliphatic sulfonic acids or their salts or their halogen derivatives having maximum 2 C atoms and maximum 6 sulfonic acid groups during the electrolytic chromium-plating.
• the addition of fluoro compounds are also mentioned.
• the working current density ranges from 10 to 1200 A/dm 2 .
• ammonium fluorooctan sulfonate is applied as wetting agent based on 300 g/l CrO 3 and 1.3% (related to CrO 3 ) H 2 SO 4 , the current density is 50 A/dm 2 and the temperature 55° C.; the additive is a saturated aliphatic sulfonic acid having 1 C and 1 sulfonic acid group (3.2 g/l).
• the galvanic chromium electrolytes of DE-A 43 05 732 contains 0,4 to 10 g 1,3-propandisulfonic acid-2-sulfinic acid and/or 1,2,3-propantrisulfonic acid or the salts thereof besides 150 to 400 g/l CrO 3 and 1 to 4% by weight (related to CrO 3 ) H 2 SO 4 .
• 3 to 5 g additive are applied at 55° C. and a current density of 50 A/dm 2 .
• the galvanic chromium electrolyte of DE-C 44 30 923 contains 2 to 10 g/l methansulfonic acid and 2 to 20 g/l MgSiF 6 as additive to CrO 3 . In a specific example there are also 0,1 ml/l tetraethylammonium perfluorooctyl sulfonate and 1 g/l sugar present.
• the chromium deposition is conducted at 40° C. and a current density of 1.82 A/dm 2 and during 1 h.
• a chromium electrolyte is known containing besides 100 to 600 g/l CrO 3 and sulphate ions in a relation of Cr 6 +to S 0 4 2 ⁇ from 90 to 120 to 1 additionally 0.01 to 3.0 g/l Na-2-hydroxyethan sulfonate or its free acid.
• the chromium deposition is conducted in 3 steps from 44 to 57° C. during more than 1 h.
• the chromium layers of De-A 102 55 853 are produced in an electrolyte containing 50 to 600 g/l CrO 3 , 0,5 to 10 g/l H 2 SO 4 , 1 to 20 g/l of an aliphatic sulfonic acid having 1 to 6 C atoms and 10 to 200 g/l of a molybdate, vanadate or zirkonate.
• the electrolyte contains 250 g/l CrO 3 , 2.5 g/l H 2 SO 4 , 4 g/l methan sulfonic acid and 100 g/l (NH 4 ) 8 Mo 7 O 24 ⁇ 4 H 2 O; the electrolyse is conducted at 55° C. and at a current density of 40 A/dm 2 during 30 min. or at 50 A/dm 2 during 120 min.
• the electrolyte of DE-B 10 2004 019 370 does not contain—compared with the beforementioned solution—molybdates, vanadates or zirkonates.
• methan sulfonic acid as a solution of 70%
• methan sulfonic acid in an amount of 9 ml/l at 60 to 70° C. during 30 min. at 30 to 80 A/dm 2 is applied.
• the current efficiency is at ⁇ 12% (as in the beforementioned solution).
• chromium electrolytes known from the prior art are either only suitable for very specific applications, or show the disadvantages—already discussed before—caused by a fluoro part in the additive molecule.
• an additive for aqueous chromic acid solutions being free of fluorine surfactants and being biodegradable and having in a chromic acid solution which contains the said additive a surface tension of ⁇ 35 mN/m, and having in the application in the electrolytical chromium-plating, determined at 45° C. and 6000 Ah of charge passage, in the chromic acid solution which contains the said additive a stability of ⁇ 4 h.
• additive within the present invention can relate either to an individual substance or to a substance mixture; for reasons of readability and clarity, however, “additive” is only referred to in the singular within the present invention. If the additive used is a substance mixture, what is meant in general is that the substance mixture has the properties described, but the individual components of the mixture may also only have the properties described.
• “stability” means especially the lasting efficacy of the additive with regard to the surface tension under the chemically demanding conditions of a chromium electrolyte in the application in the electrolytical chromium-plating.
• “stability” over a certain period means that the surface tension increases by not more than 5 mN/m over this time.
• chromium electrolyte(s) and/or “chromic acid solution(s)” are understood to mean chromium electrolytes or chromic acid solutions which—besides chromic acid and water—comprises catalysts and/or further acids among other components.
• a chromic acid solution which contains e.g. 0.1 g/l of additive and 250 g/l of chromic acid, preferably has a surface tension of ⁇ 28 mN/m, even more preferably ⁇ 25 mN.
• a chromic acid solution which contains e.g. 0.1 g/l of additive and 400 g/l of chromic acid, preferably has a surface tension of ⁇ 35 mN/m, even more preferably ⁇ 30 mN/m.
• An additive according to the present invention has at 45° C. in a chromium electrolyte which contains 0.1 g/l and 270 g/l of chromic acid preferably has a stability of ⁇ 8 h, even more preferably of ⁇ 12 h.
• the additive is free of fluorine surfactants. This is understood to mean especially that the additive does not contain any organofluorine compound, or that the proportion of organofluorine compounds in the additive is below the detection limit. Furthermore, the additive is biodegradable. This is understood to mean especially that, according to OECD criteria, ⁇ 99.5%, preferably ⁇ 99.8%, of the additive has degraded in the screening test after 8 days. In many applications, such an additive contributes to minimizing expenditure with regard to preventing the contamination of the environment, or even to making it entirely superfluous.
• a chromium electrolyte which contains e.g. 0.1 g/l of additive and 250 g/l of chromic acid, preferably has a current density of 30 A/dm 2 to 60 A/dm 2 , even more preferably 40 A/dm 2 to 50 A/dm 2 .
• a chromium electrolyte which contains e.g. 0.2 g/l of additive and 350 to 400 g/l of chromic acid, preferably has a current density of 5 A/dm 2 to 25 A/dm 2 , even more preferably 8 A/dm 2 to 20 A/dm 2 .
• the additive comprises at least a surfactant selected from the group consisting of long-chain alkylmonosulphonic acids, long-chain alkyldisulphonic acids, long-chain alkylpolysulphonic acids, salts of the long-chain alkylmonosulphonic acids, salts of the long-chain alkyldisulphonic acids and salts of the long-chain alkylpolysulphonic acids.
• long-chain is understood to mean at least 4 C atoms.
• the long-chain alkyl radicals are preferably unbranched, but it is also possible to use branched alkylmono-,-di- and -polysulphonic acids and salts thereof.
• the salts used are alkali metal salts, alkaline earth metal salts, NH 4 + salts, NR 4 + salts (where R ⁇ C 1 to C 4 alkyl).
• Polysulphonic acids have 3 to 6 sulfonic acid group per molecule.
• the additive comprises, as surfactant at least one compound CH 3 (CH 2 )nSO 3 H or salts thereof, where n is 10 to 18. In practice, these compounds often have a particularly elevated stability and are preferred in this respect. More preferably, the additive comprises such surfactants, where n is 12 to 17; even more preferably n is 14 to 16.
• the present invention also relates to use of the inventive additive as a smoothing agent in chromium electrolytes.
• concentration of additive is between 0.05 g/l and 20 g/l, preferably from 0.1 g/l to 10 g/l, and more preferably from 1 g/l to 3 g/l.
• the present invention also relates to use of the inventive additive as an additive in polymer mordants. It has been found that, surprisingly, the inventive additive can be used not only in chromium electrolytes but also in this pretreatment of polymer metallizations. In these mordants, the additive has a wetting effect and lowers the surface tension of the chromic acid-containing mordants. The positive influence on chromic acid mist formation and entrainment is comparable to the effects described above for chromium electrolytes.
• the amounts of surfactant in a chromic acid-containing mordant are basically identical with its amounts in chromium electrolytes.
• a black chromium coating was performed in
• the chromic acid solution continued to be stable after an application time of 4 h during the electrolytical chromium-plating, i.e. the surface tension is only increased by much less than 5 mN/m.
• the chromium layer deposited had a very uniform appearance.
• the dispersibility of the electrolyte was improved.
• the testing of several sheets gave a dispersion of the chromium layer which was improved by an average of 1.0 to 1.5 cm according to corresponding tests in a Hull cell.
• the surface tension was measured with a K8 tensiometer from Krüss GmbH in Hamburg.
• the unit works by the Du Noüy ring method.
• the force of a liquid lamella drawn up by the ring is measured.
• the liquid is raised until there is contact of the ring with the surface.
• With the aid of a torsion balance the force required to raise the platinum ring is measured.
• At the point of the highest force applied when the liquid lamella breaks off, there is a force equilibrium from which the surface tension of the liquid can be calculated.
• the ring geometry is taken into account by means of an instrument-specific calibration by the manufacturer.
• the current density is determined by means of a measurement of the currents with an amperemeter and reference to the known surface geometry of the components to be chromium-plated.
• the dispersibility of an electrolyte is determined by the evaluation of sheets after tests with the electrolyte in a Hull cell.
• the dispersion of the chromium layer is determined by measuring the expansion of the coated surface on the sheet after it has passed through the test run. The measurement is effected with a ruler. In general, several sheets are coated and measured under the same conditions in order to obtain reliable averages.

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• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Electrochemistry (AREA)
• Metallurgy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Emulsifying, Dispersing, Foam-Producing Or Wetting Agents (AREA)
• Electroplating Methods And Accessories (AREA)
• Primary Cells (AREA)
• Chemical Treatment Of Metals (AREA)
• Chemically Coating (AREA)

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Citations (10)

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• 2006
  • 2006-09-05 DE DE102006042076A patent/DE102006042076A1/de not_active Ceased
• 2007
  • 2007-09-04 US US11/849,491 patent/US20080142372A1/en not_active Abandoned
  • 2007-09-05 EA EA200970249A patent/EA016032B1/ru not_active IP Right Cessation
  • 2007-09-05 RS RSP-2009/0102A patent/RS20090102A/sr unknown
  • 2007-09-05 AU AU2007293648A patent/AU2007293648A1/en not_active Abandoned
  • 2007-09-05 JP JP2009527138A patent/JP5588677B2/ja active Active
  • 2007-09-05 BR BRPI0716255-3A patent/BRPI0716255A2/pt not_active IP Right Cessation
  • 2007-09-05 MX MX2009002410A patent/MX2009002410A/es unknown
  • 2007-09-05 KR KR1020097006769A patent/KR20090075677A/ko not_active Application Discontinuation
  • 2007-09-05 CA CA002662238A patent/CA2662238A1/en not_active Abandoned
  • 2007-09-05 EP EP07803268A patent/EP2061916A1/de not_active Withdrawn
  • 2007-09-05 WO PCT/EP2007/059308 patent/WO2008028932A1/de active Application Filing
  • 2007-09-05 SG SG2011063302A patent/SG174763A1/en unknown
• 2009
  • 2009-03-04 ZA ZA2009/01539A patent/ZA200901539B/en unknown
  • 2009-03-05 IL IL197411A patent/IL197411A0/en unknown
  • 2009-04-02 NO NO20091361A patent/NO20091361L/no not_active Application Discontinuation
• 2011
  • 2011-06-14 US US13/160,292 patent/US20110290658A1/en not_active Abandoned

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