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
• • 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
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
• • 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
  • C25D3/42—Electroplating: Baths therefor from solutions of light metals

Definitions

• the invention is directed to an electrolyte for the galvanic deposition of aluminum-magnesium alloys, said electrolyte containing at least one organoaluminum complex compound and an alkylmagnesium compound.
• the invention is also directed to a method for producing said electrolyte, to a coating method, to the use of the electrolyte, and to an electrolysis kit.
• magnesium-aluminum-organic complex compounds have been used for the electrolytic deposition of aluminum-magnesium alloys, and this has been described in WO 00/32847 A1.
• electrolytic coating of metallic workpieces with aluminum-magnesium alloys because of the excellent corrosion protection as a result of the aluminum-magnesium layers and because of the ecological safety thereof. Therefore, electroplating using magnesium-aluminum-organic electrolytes operating at temperatures ranging from 60 to 150° C. in closed systems has gained major technical importance.
• WO 00/32847 A1 suggests complex compounds of the general type MAlR 4 and mixtures thereof in combination with aluminum alkyls AlR 3 as particularly suitable electrolytes. They are used in the form of solutions in liquid, aromatic hydrocarbons.
• M can be an alkali metal such as sodium, potassium, rubidium and cesium, R represents alkyl residues with preferably one, two or four carbon atoms.
• the above-mentioned starting electrolyte free of magnesium is initially placed in electrolytic cells suitable for coating. Thereafter, the required organic magnesium complex is electrochemically generated in situ by applying a current, using separate aluminum and magnesium anodes or an aluminum-magnesium mixed electrode, until the concentration of magnesium complex required for coating is achieved in the electrolyte.
• deposition of aluminum-magnesium layers already takes place in the system before that point in time, i.e., before reaching the necessary concentration of magnesium complex, which is undesirable because these layers do not have the proper composition of Al and Mg.
• a magnesium-aluminum alkyl complex Mg[Al(Et) 4 ] 2
• Mg[Al(Et) 4 ] 2 is employed in the electrolyte. While this method can be performed on a laboratory scale, it involves the drawback that it cannot be performed on an industrial scale because the above complex is not industrially available, and the production thereof is highly complex and costly.
• the technical object of the invention is therefore to provide an electrolyte which can be produced in a preferably simple, efficient fashion and at low cost, which allows commercial introduction of the aluminum-magnesium coating process and avoids the need of the above-mentioned conditioning phase to form organic Mg complexes.
• an electrolyte for the galvanic deposition of aluminum-magnesium alloys containing at least one organoaluminum complex compound of formula MAlR 4 or mixtures thereof and an alkylmagnesium compound, in which formula M represents sodium, potassium, rubidium or cesium, and R represents a C 1 -C 10 alkyl group, preferably a C 1 -C 4 alkyl group.
• the electrolyte additionally includes a trialkylaluminum compound.
• the electrolyte of the invention can be used in the coating of materials with aluminum-magnesium alloys, without requiring in situ production of organomagnesium complexes in a time- and cost-intensive conditioning phase prior to the actual coating process.
• the alkylmagnesium compound is included in the electrolyte in an amount of from 0.01 to 10 mole-%, preferably from 0.1 to 1 mole-%, relative to the aluminum complex.
• Particularly preferred alkylmagnesium compounds used in the electrolyte are selected from the group of Mgbutyl 1.5 octyl 0.5 , Mgbutyl 1.0 ethyl 1.0 , Mgsec-butyl 1.0 n-butyl 1.0 or mixtures thereof.
• the organoaluminum complex compound and the alkylmagnesium compound can preferably be present in an organic solvent.
• the organic solvent is an aromatic solvent, in which case solvents such as benzene, toluene or xylene or mixtures thereof can be used.
• the alkylmagnesium compounds specified above have the advantage of being industrially available and allowing easy and low-cost production.
• the production of the electrolyte proceeds according to the following steps. Initially, the organoaluminum complex compound of formula MAlR 4 or a mixture thereof, optionally in combination with trialkylaluminum, is supplied. This is followed by addition of an alkylmagnesium compound as described above.
• M and R have the same meanings as described above.
• Metering of the alkylmagnesium compound during production of the electrolyte has the advantage that the required concentration of magnesium and aluminum can be adjusted directly, making it possible to do completely without the conditioning process specified above. Furthermore, it is possible to add the alkylmagnesium compound even during the coating process in order to maintain the appropriate magnesium concentration which is desired and required for coating.
• the alkylmagnesium compounds are added dissolved in a hydrocarbon, and the alkylaluminum complexes are supplied dissolved in an aromatic hydrocarbon.
• the hydrocarbon for the aluminum compound is selected from the group of i-pentane, n-pentane, hexane, n-hexane, heptane, n-heptane, toluene and xylene.
• electrolyte according to the invention aluminum-magnesium layers of varying concentration sequences of aluminum and magnesium can be produced in a single operation by simple and free selection of the added quantity of organomagnesium compounds.
• the appropriate concentration of aluminum-magnesium is adjusted via the added amount of organomagnesium compound.
• the electrolyte according to the invention also has the advantage of good conductivity and throwing power
• the electrolyte according to the invention allows operation with indifferent anodes used in coating parts of geometrically complicated shape.
• In-different electrodes are those not undergoing dissolution during the coating process, i.e., not consisting of Al or Mg or alloys thereof.
• organomagnesium and organoaluminum compounds must therefore be metered into the electrolyte solution.
• the appropriate concentration of aluminum-magnesium is adjusted via the added amount of organomagnesium compounds and organoaluminum compounds.
• working with indifferent anodes in in situ production of organomagnesium complexes has been excluded, in principle, which also applies to the production of layers of varying aluminum-magnesium composition in a single operation. This is not possible either in the above-described in situ process using a conditioning step to furnish the magnesium concentration in the electrolyte.
• the invention is also directed to an electrolysis kit for the galvanic deposition of aluminum-magnesium alloys on electrically conducting materials or electrically conducting layers, including:
• the compounds a) and b) are dissolved in an organic solvent.
• the invention is also directed to a method of coating electrically conducting materials or layers with aluminum-magnesium alloys using the electrolyte in accordance with claims 1 to 9 , in which method the alkylmagnesium compound in accordance with claims 1 , 3 , 5 and 6 is metered in the desired amount during the coating phase in order to obtain or maintain a desired concentration of magnesium and aluminum.
• the invention is also directed to the use of the electrolyte according to the invention for the production of layers of aluminum alloys on electrically conducting materials or electrically conducting layers.
• the entire implementation of the reaction was under argon protective gas.
• Step 1 Following removal of heptane by condensation, the BOMAG®/heptane solution was adjusted to a content of 0.32 mmol/g using toluene.
• Step 2 55.4 g of an electrolyte having the following composition: 0.8 K[Al(Et) 4 ]+0.2 Na[Al(Et) 4 ]+1.17 Al(Et) 3 +3.85 toluene was added with 2.85 g of BOMAG/toluene solution (about 1.0 mole-%, relative to the electrolyte formulation).
• Deposition was started at a current density of 0.05 A/dm 2 . After a few minutes, a bright overlay could be seen on the parts to be coated. The current density was gradually raised to 3.0 A/dm 2 . Deposition was terminated after a current quantity of 1.499 mF, corresponding to a layer thickness of 5 ⁇ m. The layer is bright and silvery.
• RF analysis of the layer 26.79 wt.-% Mg, 73.21 wt.-% Al
• the reaction was effected under argon protective gas.
• Step 1 Following removal of heptane by condensation, the BEM/heptane solution was adjusted to a content of 0.41 mmol/g using toluene.
• Step 2 60.6 g of an electrolyte having the following composition: 0.8 K[Al(Et) 4 ]+0.2 Na[Al(Et) 4 ]+1.17 Al(Et) 3 +3.85 toluene was added with 2.0 ml of BEM/toluene solution (about 0.9 mole-%, relative to the electrolyte formulation). About 62 g of an electrolyte was obtained.
• Example 1 The deposition conditions were as in Example 1. Deposition was started directly with a current density of 2.0 A/dm 2 which remained unchanged during the entire electrolysis. There was an instantaneous bright deposition of Al/Mg. Deposition was terminated after a current quantity of 3.38 mF, corresponding to a layer thickness of 11 ⁇ m. An excellent, highly uniform, silvery layer with no recognizable flaws was obtained.
• the reaction was effected under argon as protective gas.
• Step 1 The BEM/isopentane solution with a content of 1.85 mmol/g Mg component is used without further pretreatment.
• Step 2 70.04 g of an electrolyte having the following composition: 0.85 K[Al(Et) 4 ]+0.15 Na[Al(Et) 4 ]+1.08 Al(Et) 3 +3.15 toluene was added with 0.5 g of BEM/isopentane solution (about 0.8 mole-%, relative to the electrolyte formulation).
• the deposition conditions were as described in Example 1. Deposition was effected at a current density of 1.0 to 3.0 A/d m 2 . Deposition was terminated after a current quantity of 6.8 mF, corresponding to a layer thickness of 20 ⁇ m. A highly uniform, silvery layer was obtained.
• Conditioning step 2 After replacing the cathode, conditioning was continued at 1.0 to 1.2A/dm 2 . After a current quantity of 7.24 mF, with scarcely improved throwing power, a markedly brighter layer faintly lustrous in parts was obtained.
• Conditioning step 4 Reaching the final condition, a lustrous coating was obtained using a current density of 3.0 A/dm 2 , with throwing power unchanged compared to step 3.
• the current quantity was 3.73 mF.
• the electrolyte is conditioned and operational only after this procedure.

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• Chemical Kinetics & Catalysis (AREA)
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• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Electroplating Methods And Accessories (AREA)

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• 2003
  • 2003-09-27 EP EP03021877A patent/EP1518945A1/de not_active Withdrawn
• 2004
  • 2004-09-09 US US10/573,519 patent/US20070108061A1/en not_active Abandoned
  • 2004-09-09 CN CNA2004800280473A patent/CN1860257A/zh active Pending
  • 2004-09-09 JP JP2006527396A patent/JP2007506862A/ja active Pending
  • 2004-09-09 WO PCT/EP2004/052113 patent/WO2005033374A1/de active Application Filing
  • 2004-09-09 KR KR1020067005934A patent/KR20060090816A/ko not_active Application Discontinuation
  • 2004-09-09 EP EP04787118A patent/EP1664389A1/de not_active Withdrawn
  • 2004-09-09 RU RU2006116263/02A patent/RU2347857C2/ru not_active IP Right Cessation

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