EP1141447B1 - Aluminium organic electrolytes and method for electrolytic coating with aluminium or aluminium-magnesium-alloys - Google Patents

Aluminium organic electrolytes and method for electrolytic coating with aluminium or aluminium-magnesium-alloys Download PDF

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EP1141447B1
EP1141447B1 EP99962174A EP99962174A EP1141447B1 EP 1141447 B1 EP1141447 B1 EP 1141447B1 EP 99962174 A EP99962174 A EP 99962174A EP 99962174 A EP99962174 A EP 99962174A EP 1141447 B1 EP1141447 B1 EP 1141447B1
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magnesium
alet
aluminum
electrolyte
electrolyte according
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EP1141447A2 (en
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Herbert Lehmkuhl
Klaus-Dieter Mehler
Bertram Reinhold
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Aluminal Oberflachentechnik GmbH
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Studiengesellschaft Kohle gGmbH
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    • 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
    • C25D3/44—Aluminium

Definitions

  • the invention relates to organoaluminum electrolytes used for electrolytic Deposition of aluminum-magnesium alloys electrically conductive materials are suitable, as well as a process for this Use of soluble aluminum and magnesium anodes or an anode made of aluminum-magnesium alloy.
  • Organometallic complex compounds have been used for a long time for the electrolytic deposition of aluminum (dissertation H. Lehmkuhl, TH Aachen 1954, DE-PS 1047450; K. Ziegler, H. Lehmkuhl, Z. inorganic chemistry 283 (1956) 414; DE- PS 1056377; H. Lehmkuhl, R. Schfer, K. Ziegler Chem. Lng. Tech. 36 (1964) 616; EP-A 0084816; H. Lehmkuhl, K. Mehler and U. Landau in Adv. In electrochemical science and Engineering (Ed. H. Gerischer, CW Tobias) Vol. 3, Weinheim 1994).
  • MX 2 AlR 3 Complex compounds of the general type MX 2 AlR 3 , which are used either as molten salts or in the form of their solutions in liquid aromatic hydrocarbons, have been proposed as suitable electrolytes.
  • MX can be either alkali metal (Na, K, Rb, Cs) or onium halides, preferably their fluorides.
  • R are alkyl radicals with preferably one, two or four carbon atoms.
  • Gneupel obtained from a similar electrolyte from AlCl 3 , Li [AlH 4 ], MgBr 2 in a mixture of THF, diethyl ether and benzene (Mg / Al 0.6) metal deposits with up to 13% Mg (DDR patent 244573 A1).
  • the same authors describe an electrolyte solution consisting of ethyl magnesium bromide and triethyl aluminum in THF / toluene 1: 1, from which metal layers with a max. 10% Al were obtained.
  • R Et, iso-Bu
  • X F, Cl
  • M K, Cs, N
  • An electrolyte of type I according to the invention is dissolved in 2.5-6 mol per mol of complex compound of an aromatic hydrocarbon which is liquid at 20 ° C., preferably in toluene or a liquid xylene.
  • the trialkyl aluminum is preferably triethyl aluminum (AlEt 3 ), alkali tetraalkyl aluminum is preferably a mixture of potassium and sodium tetraethyl aluminum.
  • the quantitative ratio of complex: AlEt 3 is 1: 0.5 to 1: 3, preferably 1: 2.
  • the proportion of Na [AlEt 4 ] is between 0 and 25 mol%, based on the total amount of K [AlEt 4 ] and Na [AlEt 4 ], but preferably between 5 and 20 mol%.
  • the addition of small amounts of Na [AlEt 4 ] is preferred because, in the absence of this component, the aluminum anodes can only be dissolved with moderate to poor current yields, e.g. 3 AlEt 3 were as in K [AlEt 4] / / what if prolonged electrolysis lead 6 toluene only at about 22% to a loss of triethylaluminum.
  • the electrolysis is carried out at temperatures between 80 and 105 ° C., preferably between 90 and 100 ° C.
  • An exemplary electrolyte I is: 0.8 mol K [AlEt 4 ] / 0.2 mol Na [AlEt 4 ] / 2.0 mol AlEt 3 / 3.3 mol toluene. No crystallization takes place from this electrolyte solution even when standing at room temperature for a long time; the specific conductivity at 95 ° C is 13.8 mS ⁇ cm -1 .
  • Type II electrolytes preferably consist of mixtures of Na [Et 3 Al-H-AlEt 3 ], Na [AlEt 4 ] and AlEt 3 .
  • AlEt 3 ensures that Na [AlEt 4 ] no sodium metal (W. Grimme, dissertation TH Aachen (1960); DBP 1114330 (1959); DBP 1146258 (1961)), but aluminum metal is electrolytically deposited.
  • the electrolyte II according to the invention is dissolved in 5-7 mol per mol Na [AlEt 4 ] of an aromatic hydrocarbon liquid at 20 ° C., preferably in toluene or a liquid xylene.
  • the quantitative ratio Na [Et 3 Al-H-AlEt 3 ] to Na [AlEt 4 ] is preferably 2: 1 to ensure homogeneous solubility in 6 mol toluene per mol Na [AlEt 4 ] and the molar ratio Na [AlEt 4 ] to AlEt 3 is preferably 1: 2 in order to ensure perfect metal deposition by electrolysis.
  • An exemplary electrolyte is II: 1 mol of Na [Et 3 Al-H-AlEt 3] / 0.5 mol of Na [AlEt 4] / 1 mol of AlEt 3/3 mol of toluene. Even when standing at room temperature for a prolonged period, there is no crystallization from this electrolyte solution, which would interfere with the technical usability of the electrolyte.
  • the specific conductivity at 95 ° C is 8.12 mS ⁇ cm -1 .
  • the electrolytic deposition leads from the electrolytes according to the invention to aluminum-magnesium alloy layers, which differ in their electrochemical Clearly differentiate properties from previously known layer systems.
  • the electrochemical behavior of the alloy layers corresponds in the cathodic partial reaction the magnesium type, in the anodic partial reaction the aluminum type combined with a pronounced passivity interval.
  • the alloy layers exhibit at room temperature in a 5% aqueous NaCl solution with a pH of 9.0 has a quiescent current potential of about -1380 to -1500 mV vs. S.C.E. at Mg incorporation rates of 5 to 50% by weight. Due to the layer passivity (formation of intermetallic phases) the partial cathodic reaction in contact with more electronegative metals, such as magnesium, additionally inhibited. The potential of the cathodic partial reaction is thereby compared to the rest potential to even more negative potential values postponed. As a result, the remaining potential difference between the cathodic partial reaction of the alloy layer (at pH 9 Oxygen reduction) and the anodic partial reaction of the magnesium is reduced.
  • the AlMg alloy layers therefore enable one extensive adaptation to the quiescent current potential of the magnesium alloy AZ91hp, which at around -1680 mV vs. S.C.E. contact corrosion on the magnesium is greatly reduced.
  • the alloy layers are therefore suitable for the Coating steel fasteners in contact with magnesium.
  • the Application potential here particularly affects applications in the automotive industry in the transmission, engine and body area.
  • the developed alloy layers which consist of non-aqueous electrolytes are also suitable as a high-quality surface coating for highly tempered steel parts with tensile strength> 1000 MPa lies and that not with conventional galvanic processes - due to the danger of hydrogen embrittlement - can be coated. Consequently there is a potential field of application for the coating of Quenched and tempered steels with alkali-resistant as well as aluminum or Magnesium compatible coatings.
  • 1 to 9 relate to electrolyte I
  • 10 to 14 relate to electrolyte II
  • an Rb [Al (Et) 4 ] electrolyte was used.
  • An electrolyte of the composition M [AlEt 4] / 3 AlEt 3/6 Toluene (M 20 mol% Na, 80 mol% K) was located between the anode and Al-Mg-Cu-anode rotating round cathode at 91-95 ° C electrolyzed.
  • the current densities were regulated to 0.4 A ⁇ dm -2 for the Al anode and to 0.2 A ⁇ dm -2 for the Mg anode, the amount of current was 3.5 mF.
  • the amount of toluene can gradually decrease due to evaporation, if it drops below 5 moles of toluene per mole of M [AlEt 4 ], the solution becomes inhomogeneous and some AlEt 3 separates in the form of an oil Droplets. In this case the amount of toluene must be increased to 6 mol toluene per mol M [AlEt 4 ].
  • Example 3 The electrolyte of Example 3 was again electrolyzed after replacing the cathode with a new copper sheet at 90-95 ° C.
  • the cathode current density was 0.9 A ⁇ dm -2 .
  • the cathode layer was even and shiny silver. It contained 54.9% by weight of Al and 45.1% by weight of Mg.
  • the electrolyte of Examples 3 and 4 was electrolyzed four times in a row using only one magnesium anode.
  • the nature of the cathode layer and the Al and Mg content of the electrolyte are shown in Table 1.
  • Experiment No. Cathode layer appearance % By weight Electrolyte content in mAt / g al mg al mg 1 even, light gray 76.20 23.80 2 even, getting rougher on the edges 53.00 47.00 2.93 0040 3 gray, rough on the edges 29.95 70.05 2.80 0058 4 gray, rough dendritic on the edges 4.60 95.40 2.85 0070
  • An electrolyte with the composition 0.8 mol K [AlEt 4 ] /0.2 mol Na [AlEt 4 ] /2.0 AlEt 3 /3.3 mol toluene was between 2 anodes made of an aluminum-magnesium alloy with 25 wt .-% Mg and 75 wt .-% % Al and a rotating cylindrical screw M8 made of tempered steel (8.8) at 97-102 ° C with a cathodic current density of 0.8 A dm -2 and a current of 2.89 mF electrolyzed. Cathodic and anodic current yields were quantitative at 99.5%. The approximately 9 ⁇ m thick alloy layer was uniform, shiny silver and adhered well to the base material.
  • the anodic current efficiency was 98.8%.
  • the approximately 10 ⁇ m thick alloy layer was very even, matt silver and adhered well to the base material.
  • Example 7 was replaced ten times after each time the cathodes were replaced repeated an uncoated screw at 98 - 100 ° C.
  • the respective thicknesses the cathode layer was varied from 9 to 13 ⁇ m.
  • the anodic current efficiency was 99.5% over the ten trials.
  • the electrolyte obtained in the course of Example 10 was electrolyzed at 93-98 ° C. between the Al and Mg anode and a slowly rotating cylindrical cathode made from tempered steel (8.8).
  • the anodic current density was 0.3 A ⁇ dm -2 at each anode.
  • the anodic current yield was quantitative, the cathodically deposited layer was uniform and matt silver.
  • Example 11 The electrolyte of Example 11 was electrolyzed after replacing the cathode with a new one, also made of tempering steel, at 95-104 ° C.
  • the anodic current densities were set to 0.45 ADm -2 for aluminum and 0.15 ADm -2 for magnesium.
  • the anodic current yields were 90%, the cathode layer was uniform and shiny silver; According to the analysis, the layer contained 71.8% Al and 28.2% Mg, the layer thickness was 13 ⁇ m.
  • Example 12 The electrolyte of Example 12 was electrolyzed after replacing the anodes made of Al and Mg with two alloy anodes of the composition 75% by weight Al and 25% by weight Mg and after using a new cylindrical cathode made of tempering steel 8.8 at 93 ° C. During the electrolysis, the cathode slowly rotated between the two anodes, the cathodic current density was 0.8 A ⁇ dm -2 . After passing through 3.5 mF, the cathode layer was 12 ⁇ m thick and was uniform and matt silver.
  • Example 13 was performed three times after replacing the cathode with an uncoated one repeated at 92 - 100 ° C.
  • the respective layer thicknesses were between 10 and 15 ⁇ m varies.
  • the anodic current yield was over the 4th Trials for the alloy anodes 98.9%.
  • the calculated layer thicknesses were between 12 and 20mm.
  • the anodic current yield was 100% over 6 tests.
  • the initial composition of the layer with a fresh electrolyte was 90.96% Al and 9.04% Mg.
  • the system conditioned itself to a layer composition of 75.02% Al and 24.98% Mg.

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
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Abstract

Organoaluminum electrolytes and methods for the coating of electrically conductive materials with aluminum or aluminum-magnesium alloys, essentially and preferably consisting of Na[Et3Al-H-AlEt3] for aluminum coating, or of either K[AlEt4] or Na[Et3Al-H-AlEt3] and Na[AlEt4] and trialkylaluminum for alloy coating using solutions of these electrolytes in liquid aromatic hydrocarbons or mixtures thereof with aliphatic mono- or polybasic ethers, such as dimethoxyethane, and using soluble anodes of aluminum or of aluminum and magnesium, or of aluminum-magnesium alloy.

Description

Die Erfindung betrifft aluminiumorganische Elektrolyte, die zur elektrolytischen Abscheidung von Aluminium-Magnesium-Legierungen auf elektrisch leitenden Werkstoffen geeignet sind, sowie ein Verfahren hierzu unter Verwendung löslicher Aluminium- und Magnesiumanoden oder einer Anode aus Aluminium-Magnesium-Legierung.The invention relates to organoaluminum electrolytes used for electrolytic Deposition of aluminum-magnesium alloys electrically conductive materials are suitable, as well as a process for this Use of soluble aluminum and magnesium anodes or an anode made of aluminum-magnesium alloy.

Aluminiumorganische Komplexverbindungen werden seit längerer Zeit zur elektrolytischen Abscheidung von Aluminium verwendet (Dissertation H. Lehmkuhl, TH Aachen 1954, DE-PS 1047450; K. Ziegler, H. Lehmkuhl, Z. anorg. allg. Chemie 283 (1956) 414; DE-PS 1056377; H. Lehmkuhl, R. Schäfer, K. Ziegler Chem. lng. Tech. 36 (1964) 616; EP-A 0084816; H. Lehmkuhl, K. Mehler und U. Landau in Adv. in elektrochem. Science and Engineering (Ed. H. Gerischer, C. W. Tobias) Vol. 3, Weinheim 1994). Als geeignete Elektrolyte wurden solche Komplexverbindungen des allgemeinen Typs MX 2 AlR3 vorgeschlagen, die entweder als geschmolzene Salze oder in Form ihrer Lösungen in flüssigen aromatischen Kohlenwasserstoffen eingesetzt werden. MX können entweder Alkalimetall- (Na, K, Rb, Cs) oder Oniumhalogenide, vorzugsweise deren Fluoride sein. R sind Alkylreste mit vorzugsweise einem, zwei oder vier C-Atomen.Organometallic complex compounds have been used for a long time for the electrolytic deposition of aluminum (dissertation H. Lehmkuhl, TH Aachen 1954, DE-PS 1047450; K. Ziegler, H. Lehmkuhl, Z. inorganic chemistry 283 (1956) 414; DE- PS 1056377; H. Lehmkuhl, R. Schäfer, K. Ziegler Chem. Lng. Tech. 36 (1964) 616; EP-A 0084816; H. Lehmkuhl, K. Mehler and U. Landau in Adv. In electrochemical science and Engineering (Ed. H. Gerischer, CW Tobias) Vol. 3, Weinheim 1994). Complex compounds of the general type MX 2 AlR 3 , which are used either as molten salts or in the form of their solutions in liquid aromatic hydrocarbons, have been proposed as suitable electrolytes. MX can be either alkali metal (Na, K, Rb, Cs) or onium halides, preferably their fluorides. R are alkyl radicals with preferably one, two or four carbon atoms.

Das Interesse an elektrolytischen Beschichtungen von Metallwerkstücken mit Aluminium hat wegen des hervorragenden Korrosionsschutzes durch die Aluminiumschichten und deren ökologischer Unbedenklichkeit stark zugenommen. Deshalb hat die galvanische Beschichtung mit aluminiumorganischen Elektrolyten, die bei nur mäßig erhöhten Temperaturen zwischen 60 und 150 °C und in geschlossenen Systemen arbeiten, große technische Bedeutung.The interest in electrolytic coatings on metal workpieces Because of the excellent corrosion protection by the aluminum Aluminum layers and their ecological safety have increased significantly. That is why the galvanic coating with organo-aluminum Electrolytes at only moderately elevated temperatures between 60 and 150 ° C and work in closed systems, great technical importance.

Seitdem man in den letzten Jahren bestrebt ist, verbrauchs- und gewichtsoptimierte Kraftfahrzeuge zu entwickeln, verlangt ein konsequenter Leichtbau immer stärker den Einsatz von Aluminium oder Magnesium bzw. deren Legierungen miteinander. Die Leichtmetallmaterialien haben jedoch den Nachteil, daß sowohl Aluminium als auch Magnesium in wässrigem Milieu einen hohen Lösungsdruck besitzen. Vor allem bei Kontakt mit Stählen oder konventionell verzinkten Stählen gibt es Kontaktkorrosion. Aus diesem Grunde ist es erforderlich, Befestigungselemente an Magnesium-Applikationen derart zu beschichten, dass einerseits Kontaktkorrosion am Magnesium vermieden, andererseits die Langzeitbeständigkeit der Beschichtung gegeben ist. Die galvanische Beschichtung der Verbindungsschrauben mit Aluminium allein erfüllt diese Aufgabe nur teilweise, da die Korrosionsprodukte des Baustoffs Magnesium alkalisch sind und die Aluminiumoberflächen der Beschichtung angreifen (B. Reinhold, S. G. Klose, J. Kopp, Mat.-wiss. u. Werkstofftech. 29, 1-8(1998).Since the last few years, efforts have been made to optimize consumption and weight Developing motor vehicles requires consistent lightweight construction more and more the use of aluminum or magnesium or their Alloys with each other. However, the light metal materials have that Disadvantage that both aluminum and magnesium in an aqueous environment have high solution pressure. Especially when in contact with steel or Conventional galvanized steels are subject to contact corrosion. For this reason it is necessary to fasten fasteners to magnesium applications in this way coat that on the one hand prevents contact corrosion on the magnesium, on the other hand, the long-term stability of the coating is given. The galvanic coating of the connecting screws with aluminum alone only partially fulfills this task as the corrosion products of the building material Magnesium are alkaline and the aluminum surfaces of the coating attack (B. Reinhold, S.G. Klose, J. Kopp, Mat.-wiss. u. Werkstofftech. 29, 1-8 (1998).

Verfahren zur galvanischen Abscheidung von Aluminium-Magnesium-Legierungen auf elektrisch leitenden Werkstoffen sind bekannt: J. H. Connor, W. E. Reed und G. B. Wood, J. Elektrochem. Sc. 104, 38-41 (1957) beschreiben nur kurz, daß sie bei der Elektrolyse von AlBr3, Li[AlH4], MgBr2 (Mg/Al = 0.8) in Diethylether eine gut aussehende Metallschicht mit 93 % Al und 7 % Mg erhalten hätten. J. Eckert und K. Gneupel erhielten aus einem ähnlichen Elektrolyten aus AlCl3, Li[AlH4], MgBr2 in einem Gemisch aus THF, Diethylether und Benzen (Mg/Al = 0.6) Metallabscheidungen mit bis zu 13 % Mg (DDR Patentschrift 244573 A1). Die Leitfähigkeit des Elektrolyten war in der Größenordnung 1 · 10-3 bis 7 · 10-3 S · cm-1. In der DDR-Patentschrift 243723 A ist von denselben Autoren eine Elektrolytlösung beschrieben aus Ethylmagnesiumbromid und Triethylaluminium in THF/Toluol 1 : 1, aus der Metallschichten mit max. 10 % Al erhalten wurden.Methods for the galvanic deposition of aluminum-magnesium alloys on electrically conductive materials are known: JH Connor, WE Reed and GB Wood, J. Elektrochem. Sc. 104, 38-41 (1957) only briefly describe that in the electrolysis of AlBr 3 , Li [AlH 4 ], MgBr 2 (Mg / Al = 0.8) in diethyl ether they have a good-looking metal layer with 93% Al and 7% Mg would have received. J. Eckert and K. Gneupel obtained from a similar electrolyte from AlCl 3 , Li [AlH 4 ], MgBr 2 in a mixture of THF, diethyl ether and benzene (Mg / Al = 0.6) metal deposits with up to 13% Mg (DDR patent 244573 A1). The conductivity of the electrolyte was of the order of 1 · 10 -3 to 7 · 10 -3 S · cm -1 . In the GDR patent 243723 A, the same authors describe an electrolyte solution consisting of ethyl magnesium bromide and triethyl aluminum in THF / toluene 1: 1, from which metal layers with a max. 10% Al were obtained.

Typische und zur Abscheidung von Aluminium auch technisch bewährte Elektrolyte auf der Basis aluminiumorganischer Komplexverbindungen vom Typ M[R3Al-X-AlR3] (R = Et, iso-Bu; X = F, Cl; M = K, Cs, N(CH3)4) wurden von A. Mayer, J. Elektrochem. Sci. 137 (1990) p. 2806 und im US-PS 4,778,575 (Priorität 18.10.1988) nach Zugabe von Trialkylaluminium (R = Et, i-Bu) und Dimethyloder Diethylmagnesium zur elektrochemischen Abscheidung von Aluminium-Magnesium-Legierungen und von Magnesium genutzt. Typical electrolytes based on organo-aluminum complex compounds of the type M [R 3 Al-X-AlR 3 ] (R = Et, iso-Bu; X = F, Cl; M = K, Cs, N), which are also technically proven for the separation of aluminum (CH 3 ) 4 ) were developed by A. Mayer, J. Elektrochem. Sci. 137 (1990) p. 2806 and in US Pat. No. 4,778,575 (priority October 18, 1988) after the addition of trialkyl aluminum (R = Et, i-Bu) and dimethyl or diethyl magnesium used for the electrochemical deposition of aluminum-magnesium alloys and of magnesium.

Bei einer technischen Anwendung dieses Verfahrens ergeben sich jedoch folgende Schwierigkeiten, die einen kontinuierlich arbeitenden Beschichtungsprozeß unmöglich machen.

  • 1. Magnesiumanoden sind im Gegensatz zu Aluminiumanoden beim Beschichtungsprozeß mit den vorgeschlagenen Elektrolyten nicht auflösbar. Eine kontinuierliche Ergänzung des Mg-Gehaltes ist durch Auflösung der Magnesiumanode bei Verwendung von Fluorid oder allgemein von Halogenid enthaltenden aluminiumorganischen Komplexen als Elektrolyte nicht möglich.
  • 2. Nach Angaben des US-Patentes 4,778,575 wird Dialkylmagnesium In etherischer Lösung zur Elektrolytbereitung eingesetzt. Bei einem kontinuierlich arbeitenden Beschichtungsverfahren müßte das Dialkylmagnesium ständig in etherischer Lösung zugeführt werden. Von Diethylether ist jedoch bekannt, daß manche Komplexe z. B. Na[Et3Al-F-AlEt3] gespalten werden in Na[Et3AlF] + Et3Al · OEt2 (K. Ziegler, R. Köster, H. Lehmkuhl, K. Reinert, Liebigs Ann. Chem. 629, 33-49 (1960)). Wollte man die Verwendung von Ether als Lösungsmittel für Dialkylmagnesium vermeiden, müßte Dialkylmagnesium zunächst etherfrei gemacht werden, was erheblichen Aufwand und Kosten erfordert, oder es müßte durch Reaktion von Magnesiummetall mit Dialkylquecksilber, einer sehr toxischen Verbindung, in etherfreier Form hergestellt werden.
  • Der vorliegenden Erfindung lag aus den bereits beschriebenen Gründen die Aufgabe zugrunde, halogenidfreie aluminiumorganische Elektrolyte zu finden, die in optimaler Weise die für eine technische Anwendung zur Abscheidung Aluminium-Magnesium-Legierungsschichten geforderten Eigenschaften, wie Löslichkeit sowohl von Aluminium- als auch von Magnesiumanoden durch Elektrolyse, möglichst hohes Leitvermögen, homogene Löslichkeit in aromatischen Lösungsmitteln, wie z. B. Toluol zwischen 20 und 105 °C, kathodische Abscheidung dichter Schichten von Aluminium-Magnesiumlegierungen mit wählbaren Mengenverhältnissen beider Komponenten von AI : Mg = 95 : 5 bis 5 : 95, in sich vereinigen.
    • When this process is used industrially, however, the following difficulties arise which make a continuously operating coating process impossible.
  • 1. In contrast to aluminum anodes, magnesium anodes cannot be dissolved in the coating process using the proposed electrolytes. Continuous addition of the Mg content is not possible by dissolving the magnesium anode when using fluoride or generally halide-containing organoaluminum complexes as electrolytes.
  • 2. According to US patent 4,778,575, dialkyl magnesium is used in ethereal solution for electrolyte preparation. In a continuously operating coating process, the dialkyl magnesium would have to be supplied continuously in ethereal solution. However, it is known from diethyl ether that some complexes e.g. B. Na [Et 3 Al-F-AlEt 3 ] can be split into Na [Et 3 AlF] + Et 3 Al · OEt 2 (K. Ziegler, R. Köster, H. Lehmkuhl, K. Reinert, Liebigs Ann. Chem 629 , 33-49 (1960)). If one wanted to avoid the use of ether as a solvent for dialkyl magnesium, dialkyl magnesium would first have to be made ether-free, which requires considerable effort and cost, or it would have to be produced in ether-free form by reacting magnesium metal with dialkyl mercury, a very toxic compound.
  • For the reasons already described, the object of the present invention was to find halide-free aluminum-organic electrolytes which optimally have the properties required for a technical application for the deposition of aluminum-magnesium alloy layers, such as solubility of both aluminum and magnesium anodes by electrolysis , the highest possible conductivity, homogeneous solubility in aromatic solvents, such as. B. toluene between 20 and 105 ° C, cathodic deposition of dense layers of aluminum-magnesium alloys with selectable proportions of both components of Al: Mg = 95: 5 to 5: 95, combine.

    • Die Aufgabe wurde von uns gelöst durch Verwendung halogenidfreier aluminiumorganischer Elektrolyte, die dadurch gekennzeichnet sind, daß sie entweder (im Falle des Elektrolyttyps I) Alkalitetraalkylaluminium M[AlR4] oder (im Falle des Elektrolyttyps II) Alkalihexaalkylhydridoaluminium und zusätzlich M[AlR4] enthalten sowie Trialkylaluminium AlR3 (R = CH3, C2H5, C3H7 oder n - oder iso-C4H9; M = Li, Na, K, Rb, Cs), während sich Elektrolyte der Zusammensetzung M[R3Al-H-AlR3] als besonders geeignet für die Herstellung von reinen Aluminiumschichten erwiesen.The problem was solved by us using halide-free organoaluminium electrolytes, which are characterized in that they contain either (in the case of the electrolyte type I) alkali tetraalkyl aluminum M [AlR 4 ] or (in the case of the electrolyte type II) alkali hexaalkylhydrido aluminum and additionally M [AlR 4 ] and trialkylaluminium AlR 3 (R = CH 3 , C 2 H 5 , C 3 H 7 or n - or iso-C 4 H 9 ; M = Li, Na, K, Rb, Cs), while electrolytes of the composition M [ R 3 Al-H-AlR 3 ] has proven to be particularly suitable for the production of pure aluminum layers.

    Aus Gründen der Optimierung von Löslichkeit, spezifischer Leitfähigkeit und guter Zugänglichkeit sind die Ethylverbindungen ( R = C2H5 = Et) bevorzugt. Ein erfindungsgemäßer Elektrolyt von Typ I wird in 2.5 - 6 mol pro mol Komplexverbindung eines bei 20 °C flüssigen aromatischen Kohlenwasserstoffs, vorzugsweise in Toluol oder einem flüssigen Xylol gelöst. Das Trialkylaluminium ist bevorzugt Triethylaluminium (AlEt3), Alkalitetraalkylaluminium ist bevorzugt eine Mischung von Kalium- und Natriumtetraethylaluminium. Das Mengenverhältnis Komplex : AlEt3 ist 1 : 0.5 bis 1 : 3, bevorzugt 1 : 2. Der Anteil an Na[AlEt4] beträgt zwischen 0 und 25 mol %, bezogen auf die Gesamtmenge K[AlEt4] und Na[AlEt4], bevorzugt jedoch zwischen 5 und 20 mol%. Der Zusatz von geringen Mengen Na[AlEt4] ist deshalb bevorzugt, weil bei Fehlen dieser Komponente die Aluminiumanoden nur noch mit mäßigen bis schlechten Stromausbeuten gelöst werden, z. B. in K[AlEt4]/3 AlEt3/6 Toluol nur noch zu ca. 22 %, was bei längerer Dauer der Elektrolyse zu einem Verlust an Triethylaluminium führen würde. Die Elektrolyse wird bei Temperaturen zwischen 80 und 105 °C, bevorzugt zwischen 90 und 100 °C, durchgeführt.For reasons of optimizing solubility, specific conductivity and good accessibility, the ethyl compounds (R = C 2 H 5 = Et) are preferred. An electrolyte of type I according to the invention is dissolved in 2.5-6 mol per mol of complex compound of an aromatic hydrocarbon which is liquid at 20 ° C., preferably in toluene or a liquid xylene. The trialkyl aluminum is preferably triethyl aluminum (AlEt 3 ), alkali tetraalkyl aluminum is preferably a mixture of potassium and sodium tetraethyl aluminum. The quantitative ratio of complex: AlEt 3 is 1: 0.5 to 1: 3, preferably 1: 2. The proportion of Na [AlEt 4 ] is between 0 and 25 mol%, based on the total amount of K [AlEt 4 ] and Na [AlEt 4 ], but preferably between 5 and 20 mol%. The addition of small amounts of Na [AlEt 4 ] is preferred because, in the absence of this component, the aluminum anodes can only be dissolved with moderate to poor current yields, e.g. 3 AlEt 3 were as in K [AlEt 4] / / what if prolonged electrolysis lead 6 toluene only at about 22% to a loss of triethylaluminum. The electrolysis is carried out at temperatures between 80 and 105 ° C., preferably between 90 and 100 ° C.

    Ein beispielhafter Elektrolyt I ist: 0.8 mol K[AlEt4] / 0.2 mol Na[AlEt4] / 2.0 mol AlEt3 / 3.3 mol Toluol. Aus dieser Elektrolytlösung erfolgt auch bei längerem Stehen bei Raumtemperatur keine Kristallisation, die spezifische Leitfähigkeit bei 95 °C beträgt 13.8 mS·cm-1.An exemplary electrolyte I is: 0.8 mol K [AlEt 4 ] / 0.2 mol Na [AlEt 4 ] / 2.0 mol AlEt 3 / 3.3 mol toluene. No crystallization takes place from this electrolyte solution even when standing at room temperature for a long time; the specific conductivity at 95 ° C is 13.8 mS · cm -1 .

    Der Zusatz von mindestens 0.3-0.5 mol Triethylaluminium ist notwendig, um die Alkalimetallabscheidung bei der Elektrolyse zu vermeiden. Die Zugabe größerer Mengen an AlEt3 (2-3 mol AlEt3 pro mol Komplex) wirkt sich sehr positiv auf die Legierungabscheidung aus, die dann erhaltenen Legierungsschichten mit 5-50 Gew.% Mg sind sehr gleichmäßig und seidigglänzend und bei 4-6 µm Schichtdicke bereits weitgehend porenfrei. Erhöht man die Menge von Triethylaluminium pro mol Komplex von 2 : 1 auf 3 : 1, muß jedoch, um eine auch bei Raumtemperatur homogene Lösung zu behalten, dem Elektrolyten weiteres Lösungsmittel zugefügt werden, und zwar insgesamt auf 5.5-6 mol Toluol pro mol Komplex. Dadurch verliert der Elektrolyt jedoch an Leitvermögen.The addition of at least 0.3-0.5 mol of triethyl aluminum is necessary to avoid the alkali metal deposition during electrolysis. The addition of larger amounts of AlEt 3 (2-3 mol AlEt 3 per mol complex) has a very positive effect on the alloy deposition, the alloy layers obtained with 5-50 wt.% Mg are very uniform and silky glossy and at 4-6 µm Layer thickness already largely non-porous. If the amount of triethylaluminum per mole of complex is increased from 2: 1 to 3: 1, further solvent must be added to the electrolyte in order to keep a homogeneous solution even at room temperature, to a total of 5.5-6 moles of toluene per mole of complex , As a result, however, the electrolyte loses conductivity.

    Elektrolyte des Typs II bestehen bevorzugt aus Mischungen von Na[Et3Al-H-AlEt3], Na[AlEt4] und AlEt3. Trotz ungünstiger Eigenschaften von Einzelkomponenten, z. B. relativ hoher Schmelzpunkt von Na[AlEt4] bei 125 °C und geringe Löslichkeit in Toluol bei 20 °C, sind Mischungen der drei Komponenten bei geeignetem Mischungsverhältnis (molares Verhältnis Na[Et3Al-H-AlEt3] zu Na[AlEt4] zwischen 4:1 bis 1:1, bevorzugt 2:1) bei 20 °C in Toluol homogen löslich und haben dann die für eine technische Anwendung zur Abscheidung von Aluminium-Magnesium-Legierungsschichten geforderten Eigenschaften, wie der Löslichkeit sowohl von Aluminium- als auch von Magnesiumanoden durch Elektrolyse, möglichst hohes Leitvermögen, homogene Löslichkeit in aromatischen Lösungsmitteln, wie z. B. in Toluol zwischen 20 und 105 °C, kathodische Abscheidung dichter Schichten von Aluminium- Magnesium-Legierungen und wählbare Mengenverhältnissen beider Komponenten von Al : Mg = 95 : 5 bis 5 : 95. Die Anwesenheit von AlEt3 sorgt dafür, daß aus Na[AlEt4] kein Natriummetall (W. Grimme, Dissertation TH Aachen (1960); DBP 1114330 (1959); DBP 1146258 (1961)), sondern Aluminiummetall elektrolytisch abgeschieden wird. Na[AlEt4] löst bei der Elektrolyse sowohl Aluminium- als auch Magnesiumanoden auf (W. Grimme, Dissertation TH Aachen 1960; K. Ziegler, H. Lehmkuhl in Methoden der Organ. Chem. (Houben-Weyl), Bd. 13,1, S. 281 (1970).Type II electrolytes preferably consist of mixtures of Na [Et 3 Al-H-AlEt 3 ], Na [AlEt 4 ] and AlEt 3 . Despite the unfavorable properties of individual components, e.g. B. relatively high melting point of Na [AlEt 4 ] at 125 ° C and low solubility in toluene at 20 ° C, are mixtures of the three components with a suitable mixing ratio (molar ratio Na [Et 3 Al-H-AlEt 3 ] to Na [ AlEt 4 ] between 4: 1 to 1: 1, preferably 2: 1) homogeneously soluble in toluene at 20 ° C. and then have the properties required for a technical application for the deposition of aluminum-magnesium alloy layers, such as the solubility of both aluminum - As well as magnesium anodes by electrolysis, the highest possible conductivity, homogeneous solubility in aromatic solvents, such as. B. in toluene between 20 and 105 ° C, cathodic deposition of dense layers of aluminum-magnesium alloys and selectable proportions of both components of Al: Mg = 95: 5 to 5: 95. The presence of AlEt 3 ensures that Na [AlEt 4 ] no sodium metal (W. Grimme, dissertation TH Aachen (1960); DBP 1114330 (1959); DBP 1146258 (1961)), but aluminum metal is electrolytically deposited. Na [AlEt 4 ] dissolves both aluminum and magnesium anodes during electrolysis (W. Grimme, dissertation TH Aachen 1960; K. Ziegler, H. Lehmkuhl in Methods of Organ. Chem. (Houben-Weyl), Vol. 13, 1, p. 281 (1970).

    Elektrolyte der Zusammensetzung M[R3AlH-AlR3], (M = Na, K, Rb, Cs; Alkylrest R = CH3, C2H5, C3H7, C4H9) z. B. Na[Et3Al-H-AlEt3] sind als Lösungen in Toluol sehr gut zur elektrolytischen Abscheidung und Auflösung von Aluminium bei 90 - 105 °C geeignet. Bei der Elektrolyse dieser Verbindung und bei Abwesenheit von erfindungsgemäßem Na[AlEt4] haben wir jedoch gefunden, daß Magnesiumanoden nicht gelöst werden. Die gleichzeitige Verwendung einer Aluminium- und einer Magnesiumanode führte nach Stromdurchgang von 8.7 mF zu einem Gewichtsverlust von 8.7 mÄq Aluminium, während die Magnesiumanode völlig ungelöst blieb. Für die Herstellung von Aluminium-Magnesium-Legierungsbeschichtungen jedoch bewirkt die Kombination beider Na-Komplexe mit Triethylaluminium und Toluol,

  • a) daß die Löslichkeit von NaAlEt4 genügend erhöht und
  • b) daß in dieser Elektrolysemischung sowohl Aluminium- als auch Magnesiumanoden gelöst werden.
    • Electrolytes of the composition M [R 3 AlH-AlR 3 ], (M = Na, K, Rb, Cs; alkyl radical R = CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 ) z. B. Na [Et 3 Al-H-AlEt 3 ] are very suitable as solutions in toluene for the electrolytic deposition and dissolution of aluminum at 90 - 105 ° C. In the electrolysis of this compound and in the absence of Na [AlEt 4 ] according to the invention, we have found that magnesium anodes are not dissolved. The simultaneous use of an aluminum and a magnesium anode led to a weight loss of 8.7 meq aluminum after a current of 8.7 mF, while the magnesium anode remained completely undissolved. However, for the production of aluminum-magnesium alloy coatings, the combination of both Na complexes with triethyl aluminum and toluene
  • a) that the solubility of NaAlEt 4 is increased sufficiently and
  • b) that both aluminum and magnesium anodes are dissolved in this electrolysis mixture.

    • Der erfindungsgemäße Elektrolyt II ist in 5 - 7 mol pro mol Na[AlEt4] eines bei 20 °C flüssigen aromatischen Kohlenwasserstoffs, vorzugsweise in Toluol oder einem flüssigen Xylol gelöst. Das Mengenverhältnis Na[Et3Al-H-AlEt3] zu Na[AlEt4] ist bevorzugt 2 : 1, um eine homogene Löslichkeit in 6 mol Toluol pro mol Na[AlEt4] sicherzustellen und das Molverhältnis Na[AlEt4] zu AlEt3 ist bevorzugt 1 : 2, um eine einwandfreie Metallabscheidung durch Elektrolyse zu gewährleisten. Ein beispielhafter Elektrolyt II ist: 1 mol Na[Et3Al-H-AlEt3] / 0.5 mol Na[AlEt4] / 1 mol AlEt3 / 3 mol Toluol. Aus dieser Elektrolytlösung erfolgt auch bei längerem Stehen bei Raumtemperatur keine Kristallisation, die eine technische Verwendbarkeit des Elektrolyten stören würde. Die spezifische Leitfähigkeit bei 95 °C beträgt 8.12 mS · cm-1.The electrolyte II according to the invention is dissolved in 5-7 mol per mol Na [AlEt 4 ] of an aromatic hydrocarbon liquid at 20 ° C., preferably in toluene or a liquid xylene. The quantitative ratio Na [Et 3 Al-H-AlEt 3 ] to Na [AlEt 4 ] is preferably 2: 1 to ensure homogeneous solubility in 6 mol toluene per mol Na [AlEt 4 ] and the molar ratio Na [AlEt 4 ] to AlEt 3 is preferably 1: 2 in order to ensure perfect metal deposition by electrolysis. An exemplary electrolyte is II: 1 mol of Na [Et 3 Al-H-AlEt 3] / 0.5 mol of Na [AlEt 4] / 1 mol of AlEt 3/3 mol of toluene. Even when standing at room temperature for a prolonged period, there is no crystallization from this electrolyte solution, which would interfere with the technical usability of the electrolyte. The specific conductivity at 95 ° C is 8.12 mS · cm -1 .

    Die elektrolytische Abscheidung von Aluminium-Magnesium-Legierungsschichten aus den erfindungsgemäßen Elektrolyten wird unter Verwendung einer löslichen Aluminium- und einer ebenfalls löslichen Magnesiumanode oder unter Verwendung einer Anode aus Aluminium-Magnesium-Legierung durchgeführt. Im Fall von zwei Anoden sind diese zur Gewährleistung einer kontinuierlichen Verfahrensweise und zur Steuerung auf eine wählbare und gewünschte Legierungszusammensetzung getrennt geschaltet. Die Elektrolysen werden In Toluollösung zweckmäßig bei 90 - 100 °C durchgeführt. Die anodischen (Al 95-100 %; Mg 93-100 %) und kathodischen Stromausbeuten sind praktisch quantitativ. Da sich eine endliche und damit notwendige Konzentration an Magnesium im Elektrolyten erst im Verlauf einer Elektrolyse aufbaut, muß vor dem Einsatz eines frisch bereiteten Elektrolyten dieser Zustand zunächst hergestellt werden. Dies kann erfolgen

  • 1. durch kurzzeitige Vorelektrolyse, während der mit ansteigender Magnesiumkonzentration in der Elektrolytlösung der Magnesiumgehalt in der kathodisch abgeschiedenen Schicht zunimmt bis zu dem Zeitpunkt, an dem durch geeignete und gewünschte Wahl der anodischen Teilstromdichten ebenso viel an Aluminium und Magnesium anodisch gelöst wie kathodisch wieder abgeschieden werden; oder
  • 2. durch Zugabe der Komplexverbindung Mg[AlEt4]2, einer farblosen Flüssigkeit (K. Ziegler, E. Holzkamp, Liebigs Ann. Chem. 605 93-97 (1957)), die auch als Lösung in Toluol verwendet werden kann. Nach Zugabe von 0.01 mol Mg[AlEt4]2 pro 3.0 mol K[AlEt4] kann z. B. der Elektrolyt I direkt zur verfahrensgemäßen Beschichtung verwendet werden.
    • The electrolytic deposition of aluminum-magnesium alloy layers from the electrolytes according to the invention is carried out using a soluble aluminum and a likewise soluble magnesium anode or using an anode made of aluminum-magnesium alloy. In the case of two anodes, these are switched separately to ensure a continuous procedure and to control a selectable and desired alloy composition. The electrolysis is expediently carried out at 90-100 ° C. in toluene solution. The anodic (Al 95-100%; Mg 93-100%) and cathodic current yields are practically quantitative. Since a finite and therefore necessary concentration of magnesium only builds up in the course of an electrolysis, this state must first be established before using a freshly prepared electrolyte. This can be done
  • 1.by short-time pre-electrolysis, during which the magnesium content in the cathodically deposited layer increases with increasing magnesium concentration in the electrolytic solution up to the point in time at which as much aluminum and magnesium are dissolved anodically as cathodically by an appropriate and desired choice of the anodic partial current densities ; or
  • 2. by adding the complex compound Mg [AlEt 4 ] 2 , a colorless liquid (K. Ziegler, E. Holzkamp, Liebigs Ann. Chem. 605 93-97 (1957)), which can also be used as a solution in toluene. After adding 0.01 mol of Mg [AlEt 4 ] 2 per 3.0 mol of K [AlEt 4 ], e.g. B. the electrolyte I can be used directly for the coating according to the process.

    • Die elektrolytische Abscheidung aus den erfindungsgemäßen Elektrolyten führt zu Aluminium-Magnesium-Legierungsschichten, die sich in ihren elektrochemischen Eigenschaften deutlich von bislang bekannten Schichtsystemen unterscheiden. Das elektrochemische Verhalten der Legierungsschichten entspricht in der kathodischen Teilreaktion dem Magnesium-Typ, in der anodischen Teilreaktion dem Aluminium-Typ verbunden mit einem ausgeprägtem Passivitätsintervall.The electrolytic deposition leads from the electrolytes according to the invention to aluminum-magnesium alloy layers, which differ in their electrochemical Clearly differentiate properties from previously known layer systems. The electrochemical behavior of the alloy layers corresponds in the cathodic partial reaction the magnesium type, in the anodic partial reaction the aluminum type combined with a pronounced passivity interval.

    Die Legierungsschichten weisen bei Raumtemperatur in einer 5 %-igen wässrigen NaCl-Lösung mit einem pH-Wert von 9,0 ein Ruhestrompotential von etwa -1380 bis -1500 mV vs. S.C.E. bei Mg-Einbauraten von 5 bis 50 Gew.-% auf. Aufgrund der Schicht-Passivität (Ausbildung intermetallischer Phasen) wird die kathodische Teilreaktion im Kontakt mit elektronegativeren Metallen, wie Magnesium, zusätzlich gehemmt. Das Potential der kathodischen Teilreaktion wird dadurch gegenüber dem Ruhepotential zu noch negativeren Potentialwerten verschoben. Dies hat zur Folge, dass die verbleibende Potentialdifferenz zwischen der kathodischen Teilreaktion der Legierungsschicht (bei pH 9 Sauerstoffreduktion) und der anodischen Teilreaktion des Magnesiums stark verringert wird. Die AlMg-Legierungsschichten ermöglichen folglich eine weitgehende Adaption an das Ruhestrompotential der Magnesium-Legierung AZ91hp, das bei ca. -1680 mV vs. S.C.E. liegt, Kontaktkorrosion am Magnesium wird stark reduziert. Daher eignen sich die Legierungsschichten für die Beschichtung von Stahl-Befestigungselementen in Kontakt mit Magnesium. Das Anwendungspotential betrifft hier insbesondere Anwendungen der Automobilindustrie im Getriebe-, Motoren- und Karrosseriebereich.The alloy layers exhibit at room temperature in a 5% aqueous NaCl solution with a pH of 9.0 has a quiescent current potential of about -1380 to -1500 mV vs. S.C.E. at Mg incorporation rates of 5 to 50% by weight. Due to the layer passivity (formation of intermetallic phases) the partial cathodic reaction in contact with more electronegative metals, such as magnesium, additionally inhibited. The potential of the cathodic partial reaction is thereby compared to the rest potential to even more negative potential values postponed. As a result, the remaining potential difference between the cathodic partial reaction of the alloy layer (at pH 9 Oxygen reduction) and the anodic partial reaction of the magnesium is reduced. The AlMg alloy layers therefore enable one extensive adaptation to the quiescent current potential of the magnesium alloy AZ91hp, which at around -1680 mV vs. S.C.E. contact corrosion on the magnesium is greatly reduced. The alloy layers are therefore suitable for the Coating steel fasteners in contact with magnesium. The Application potential here particularly affects applications in the automotive industry in the transmission, engine and body area.

    Die entwickelten Legierungsschichten, die aus nicht-wässrigen Elektrolyten abgeschieden werden, eignen sich außerdem als qualitativ hochwertige Oberflächenbeschichtung für hochvergütete Stahlteile deren Zugfestigkeit > 1000 MPa liegt und die nicht mit konventionellen galvanischen Verfahren - aufgrund der Gefahr von Wasserstoffversprödung - beschichtetet werden können. Somit ergibt sich ein potentielles Anwendungsfeld für die Beschichtung von Vergütungs- und Federstählen mit alkalibeständigen sowie Aluminium- bzw. Magnesium-verträglichen Überzügen.The developed alloy layers, which consist of non-aqueous electrolytes are also suitable as a high-quality surface coating for highly tempered steel parts with tensile strength> 1000 MPa lies and that not with conventional galvanic processes - due to the danger of hydrogen embrittlement - can be coated. Consequently there is a potential field of application for the coating of Quenched and tempered steels with alkali-resistant as well as aluminum or Magnesium compatible coatings.

    Beispiele:Examples:

    Von den nachfolgenden Beispielen beziehen sich 1 bis 9 auf den Elektrolyten I, 10 bis 14 auf den Elektrolyten II. In Beispiel 15 wurde ein Rb[Al(Et)4]-Elektrolyt eingesetzt.Of the examples below, 1 to 9 relate to electrolyte I, 10 to 14 relate to electrolyte II. In example 15, an Rb [Al (Et) 4 ] electrolyte was used.

    Beispiel 1example 1

    189.5 g (1.14 mol) Na[AlEt4] wurden mit 216.8 g (2.35 mol) Toluol auf 130 °C Badtemperatur erhitzt. Zu der in der Hitze entstehenden klaren, farblosen Lösung gibt man in kleinen Portionen 85 g (1.14 mol) getrocknetes KCI. Nach der Zugabe der Gesamtmenge rührt man 6 h nach, läßt auf Raumtemperatur abkühlen und trennt die Suspension durch Filtrieren durch eine Glasfaserhülse, man wäscht mit 105 ml (91.0 g; 1.0 mol) Toluol nach. Das Gesamtfiltrat enthält K : Na im molaren Verhältnis von 0.79 : 0.21. Andere K : Na-Verhältnisse von z. B. 0.90 : 0.10 wurden durch Mischen der reinen Komponenten K[AlEt4] und Na[AlEt4] eingestellt. 189.5 g (1.14 mol) Na [AlEt 4 ] were heated to 130 ° C bath temperature with 216.8 g (2.35 mol) toluene. 85 g (1.14 mol) of dried KCI are added in small portions to the clear, colorless solution which is formed in the heat. After the total amount has been added, the mixture is stirred for a further 6 hours, allowed to cool to room temperature and the suspension is separated by filtration through a glass fiber tube, and the mixture is washed with 105 ml (91.0 g; 1.0 mol) of toluene. The total filtrate contains K: Na in a molar ratio of 0.79: 0.21. Other K: Na ratios of e.g. B. 0.90: 0.10 were set by mixing the pure components K [AlEt 4 ] and Na [AlEt 4 ].

    Beispiel 2Example 2

    Ein Elektrolyt der Zusammensetzung M[AlEt4]/3 AlEt3 /6 Toluol (M = 20 mol% Na, 80 mol% K) wurde mit zwischen Al-Anode und Mg-Anode befindlicher rotierender runder Cu-Kathode bei 91-95 °C elektrolysiert. Die Stromdichten wurden bezüglich der Al-Anode auf 0.4 A · dm-2 und für die Mg-Anode auf 0.2 A · dm-2 reguliert, die Strommenge betrug 3.5 mF.An electrolyte of the composition M [AlEt 4] / 3 AlEt 3/6 Toluene (M = 20 mol% Na, 80 mol% K) was located between the anode and Al-Mg-Cu-anode rotating round cathode at 91-95 ° C electrolyzed. The current densities were regulated to 0.4 A · dm -2 for the Al anode and to 0.2 A · dm -2 for the Mg anode, the amount of current was 3.5 mF.

    Nach Durchgang dieser Strommenge hatten sich 2,19 m Äquivalente Al und 1,17 mÄ Mg gelöst; die anodische Stromausbeute bezogen auf Al war 95.6, bezogen auf Mg 96.7 %. Die Kathodenschicht war gleichmäßig, silberglänzend und enthielt 72.4 % Al und 27.6 % Mg, die kathodische Schicht wog 34.3 mg und war ca. 12 µm dick.After this amount of electricity had passed, 2.19 m equivalents of Al and 1.17 mA Mg dissolved; the anodic current efficiency based on Al was 95.6, based on Mg 96.7%. The cathode layer was even, shiny silver and contained 72.4% Al and 27.6% Mg, the cathodic layer weighed 34.3 mg and was about 12 µm thick.

    Bei langzeitiger Verwendung des Elektrolyten für zahlreiche Beschichtungsversuche bei 90-95 °C kann die Toluolmenge durch Verdampfung allmählich abnehmen, sinkt sie unter 5 mol Toluol pro mol M[AlEt4] wird die Lösung inhomogen, und es scheidet sich etwas AlEt3 in Form öliger Tröpfchen aus. In diesem Fall muß die Toluolmenge auf 6 mol Toluol pro mol M[AlEt4] ergänzt werden.With long-term use of the electrolyte for numerous coating experiments at 90-95 ° C, the amount of toluene can gradually decrease due to evaporation, if it drops below 5 moles of toluene per mole of M [AlEt 4 ], the solution becomes inhomogeneous and some AlEt 3 separates in the form of an oil Droplets. In this case the amount of toluene must be increased to 6 mol toluene per mol M [AlEt 4 ].

    Beispiel 3Example 3

    Ein Elektrolyt der Zusammensetzung 0.79 mol K[AlEt4]/0.21 mol Na[AlEt4]/0.3 mol AlEt3/2.5 mol Toluol wurde zwischen Aluminium- und Magnesiumanode und einer Kupferkathode bei 90-95 °C elektrolysiert. Die Kathodenstromdichte betrug 1 A · dm-2 die Strommenge war 8.65 mF. Danach hatten sich 2.77 mÄq Al und 4,76 mÄq Mg gelöst, was einer anodischen Stromausbeute von 87 % entspricht. Die Kathodenschicht war gleichmäßig und glänzend. Sie enthielt 71.0 Gew.% und 29.0 Gew.% Mg.An electrolyte with the composition 0.79 mol K [AlEt 4 ] /0.21 mol Na [AlEt 4 ] /0.3 mol AlEt 3 /2.5 mol toluene was electrolyzed between aluminum and magnesium anode and a copper cathode at 90-95 ° C. The cathode current density was 1 A · dm -2 and the amount of current was 8.65 mF. Then 2.77 meq Al and 4.76 meq Mg had dissolved, which corresponds to an anodic current efficiency of 87%. The cathode layer was even and shiny. It contained 71.0% by weight and 29.0% by weight of Mg.

    Beispiel 4Example 4

    Der Elektrolyt von Beispiel 3 wurde nach Austausch der Kathode gegen ein neues Kupferblech erneut bei 90-95 °C eiektrolysiert. Die Kathoden-Stromdichte betrug 0.9 A · dm-2. Nach Durchgang von 6.53 mF wurde der Versuch abgebrochen. Die Kathodenschicht war gleichmäßig und silberglänzend. Sie enthielt 54.9 Gew.% Al und 45.1 Gew.% Mg. The electrolyte of Example 3 was again electrolyzed after replacing the cathode with a new copper sheet at 90-95 ° C. The cathode current density was 0.9 A · dm -2 . After passing through 6.53 mF, the experiment was stopped. The cathode layer was even and shiny silver. It contained 54.9% by weight of Al and 45.1% by weight of Mg.

    Beispiel 5Example 5

    Der Elektrolyt der Beispiele 3 und 4 wurde viermal hintereinander unter Einsatz von nur einer Magnesiumanode elektrolysiert. Die Beschaffenheit der kathodenschicht und der Al- und Mg-Gehalt des Elektrolyten sind in Tabelle 1 dargestellt. Versuchs- Nr. Kathodenschicht Aussehen Gehalt in Gew.% Elektrolyt Gehalt in mAt/g Al Mg Al Mg 1 gleichmäßig, hellgrau 76.20 23.80 2 gleichmäßig, an den Kanten rauher werdend 53.00 47.00 2.93 0.040 3 grau, an den Kanten rauh 29.95 70.05 2.80 0.058 4 grau, rauh an den Kanten dendritisch 4.60 95.40 2.85 0.070 The electrolyte of Examples 3 and 4 was electrolyzed four times in a row using only one magnesium anode. The nature of the cathode layer and the Al and Mg content of the electrolyte are shown in Table 1. Experiment No. Cathode layer appearance % By weight Electrolyte content in mAt / g al mg al mg 1 even, light gray 76.20 23.80 2 even, getting rougher on the edges 53.00 47.00 2.93 0040 3 gray, rough on the edges 29.95 70.05 2.80 0058 4 gray, rough dendritic on the edges 4.60 95.40 2.85 0070

    Beispiel 6Example 6

    Ein Elektrolyt der Zusammensetzung K[AlEt4]/AlEt3/4 Toluol mit einer spezifischen Leitfähigkeit von 17.3 mS · cm-1 wurde zwischen einer aus Aluminium-Blech und Magnesium-Blech bestehenden Anode und einer aus TiAl6V4-bestehenden Kathode bei 90-95 °C elektrolysiert. Die kathodische Stromdichte war 0.4 A · dm-2, nach Durchgang von 5.59 mF waren 4.53 mÄq Magnesium und 1.02 mÄq Aluminium (= 99.3 % anodische Stromausbeute) in Lösung gegangen, die Kathodenschicht war sehr gleichmäßig und silberhell sowie haftfest auf TiAl6V4 und bestand zu 75 Gew.% aus Al und zu 25 Gew.% aus Mg.An electrolyte with the composition K [AlEt 4 ] / AlEt 3/4 toluene with a specific conductivity of 17.3 mS · cm -1 was added between an anode consisting of aluminum sheet and magnesium sheet and a cathode consisting of TiAl 6 V 4 90-95 ° C electrolyzed. The cathodic current density was 0.4 Adm -2 , after passing through 5.59 mF, 4.53 meq of magnesium and 1.02 meq of aluminum (= 99.3% anodic current yield) had dissolved, the cathode layer was very uniform and bright silver and adherent to TiAl 6 V 4 and consisted of 75% by weight of Al and 25% by weight of Mg.

    Beispiel 7Example 7

    Ein Elektrolyt der Zusammensetzung 0.8 mol K[AlEt4]/0.2 mol Na[AlEt4]/2.0 AlEt3/3.3 mol Toluol wurde zwischen 2 Anoden aus einer Aluminium-Magnesium-Legierung mit 25 Gew.-% Mg und 75 Gew.-% Al und einer rotierenden zylindrischen Schraube M8 aus Vergütungsstahl (8.8) bei 97-102 °C mit kathodischer Stromdichte von 0.8 A dm-2 und einer Strommenge von 2.89 mF elektrolysiert. Kathodische und anodische Stromausbeuten waren mit 99.5 % quantitativ. Die ca. 9 µm dicke Legierungsschicht war gleichmäßig , silbern glänzend und auf dem Grundmaterial gut haftend.An electrolyte with the composition 0.8 mol K [AlEt 4 ] /0.2 mol Na [AlEt 4 ] /2.0 AlEt 3 /3.3 mol toluene was between 2 anodes made of an aluminum-magnesium alloy with 25 wt .-% Mg and 75 wt .-% % Al and a rotating cylindrical screw M8 made of tempered steel (8.8) at 97-102 ° C with a cathodic current density of 0.8 A dm -2 and a current of 2.89 mF electrolyzed. Cathodic and anodic current yields were quantitative at 99.5%. The approximately 9 µm thick alloy layer was uniform, shiny silver and adhered well to the base material.

    Beispiel 8Example 8

    Der Elektrolyt von Beispiel 7 wurde unter Rühren mit dem bifunktionellen Ether Dimethoxiethan bis zu einem Verhältnis von AlEt3 zu DME = 1 : 0,86 versetzt. Nach Erwärmen auf 95-98 °C wurde zwischen 2 Anoden aus einer Aluminium-Magnesium-Legierung mit 25 Gew.-% Mg und 75 Gew.-% Al und einer rotierenden zylindrischen Schraube aus 8.8-Stahl mit einer kathodischen Stromdichte von 0,8 A · dm-2 und einer Strommenge von 2,99 mF elektrolysiert. Die anodische Stromausbeute betrug 98,8 %. Die ca. 10 µm dicke Legierungsschicht war sehr gleichmäßig, matt silbern und auf dem Grundmaterial gut haftend.The bifunctional ether dimethoxyethane was added to the electrolyte of Example 7 with stirring to a ratio of AlEt 3 to DME = 1: 0.86. After heating to 95-98 ° C between 2 anodes made of an aluminum-magnesium alloy with 25 wt .-% Mg and 75 wt .-% Al and a rotating cylindrical screw made of 8.8 steel with a cathodic current density of 0.8 A · dm -2 and a current of 2.99 mF electrolyzed. The anodic current efficiency was 98.8%. The approximately 10 µm thick alloy layer was very even, matt silver and adhered well to the base material.

    Beispiel 9Example 9

    Beispiel 7 wurde zehnmal nach jedesmaligem Austausch der Kathoden gegen eine unbeschichtete Schraube bei 98 - 100 °C wiederholt. Die jeweiligen Dicken der Kathodenschicht wurden von 9 bis 13 µm variiert. Die anodische Stromausbeute betrug über die zehn Versuche 99.5 %.Example 7 was replaced ten times after each time the cathodes were replaced repeated an uncoated screw at 98 - 100 ° C. The respective thicknesses the cathode layer was varied from 9 to 13 µm. The anodic current efficiency was 99.5% over the ten trials.

    Beispiel 10Example 10

    39.8 mol Na[Et3Al-H-AlEt3] und 39.8 mol Na[AlEt4] und 78.6 mol Toluol werden bei 100 °C gerührt, aus der klaren, viskosen Lösung fallen beim Abkühlen auf Raumtemperatur feine Kristalle aus. Durch Zugabe weiterer 39.8 mol Na[Et3Al-H-AlEt3] und 78.6 mol Toluol und Erwärmen auf 100 °C entsteht eine klare Lösung, die spezifische Leitfähigkeit bei 95 °C beträgt 21.8 mS · cm-1. Nach Zugabe von 39.5 mol Toluol entsteht eine Lösung mit spezifischer Leitfähigkeit von 19.1 mS · cm-1 bei 95 °C, beim Erkalten auf Raumtemperatur fallen noch einige Kristalle aus. Daher werden nochmals 39.5 mol Toluol zugegeben, aus der jetzt erhaltenen Lösung erfolgt beim Abkühlen keine Kristallisation mehr.
    Die spezifische Leitfähigkeit beträgt bei bei 95 °C 18.0 mS · cm-1. Eine Probeelektrolyse zwischen AI- und Mg-Anode und einer Stahlkathode ergab nur eine graue, rauhe und teilweise dendritische Kathodenschicht. Dem Elektrolyten wurden noch 79.8 mol AlEt3 zugefügt, die spezifische Leitfähigkeit betrug 8.12 mS · cm-1 für den jetzt erhaltenen Elektrolyten der Zusammensetzung 1 Na[Et3Al-H-AlEt3] /0.5 Na[AlEt4]/ 1 AlEt3 / 3 Toluol.    39.8 mol of Na [Et 3 Al-H-AlEt 3 ] and 39.8 mol of Na [AlEt 4 ] and 78.6 mol of toluene are stirred at 100 ° C., and fine crystals precipitate out of the clear, viscous solution on cooling to room temperature. The addition of a further 39.8 mol of Na [Et 3 Al-H-AlEt 3 ] and 78.6 mol of toluene and heating to 100 ° C. gives a clear solution, the specific conductivity at 95 ° C. is 21.8 mS · cm -1 . After adding 39.5 mol of toluene, a solution with a specific conductivity of 19.1 mS · cm -1 at 95 ° C is formed. When cooling to room temperature, some crystals still precipitate out. A further 39.5 mol of toluene are therefore added, and the solution now obtained no longer crystallizes on cooling.
    The specific conductivity is 18.0 mS · cm -1 at 95 ° C. A sample electrolysis between Al and Mg anode and a steel cathode showed only a gray, rough and partially dendritic cathode layer. 79.8 mol of AlEt 3 were added to the electrolyte; the specific conductivity was 8.12 mS · cm -1 for the electrolyte of the composition 1 Na [Et 3 Al-H-AlEt 3 ] /0.5 Na [AlEt 4 ] / 1 AlEt 3 / 3 toluene.

    Beispiel 11Example 11

    Der im Verlauf von Beispiel 10 erhaltene Elektrolyt wurde bei 93-98 °C zwischen Al- und Mg-Anode und einer langsam rotierenden zylindrischen Kathode aus Vergütungsstahl (8.8) elektrolysiert. Die anodische Stromdichte war an jeder Anode je 0.3 A · dm-2. Nach Durchgang von 1.6 mF an jeder Anode war die anodische Stromausbeute quantitativ, die kathodisch abgeschiedene Schicht war einheitlich und mattsilbern.The electrolyte obtained in the course of Example 10 was electrolyzed at 93-98 ° C. between the Al and Mg anode and a slowly rotating cylindrical cathode made from tempered steel (8.8). The anodic current density was 0.3 A · dm -2 at each anode. After passage of 1.6 mF at each anode, the anodic current yield was quantitative, the cathodically deposited layer was uniform and matt silver.

    Beispiel 12Example 12

    Der Elektrolyt des Beispiels 11 wurde nach Austausch der Kathode gegen eine neue, ebenfalls aus Vergütungsstahl, bei 95 - 104 °C elektrolysiert. Die anodischen Stromdichten wurden auf 0.45 A · dm-2 für Aluminium- und 0.15 A · dm-2 für Magnesium eingestellt. Die anodischen Stromausbeuten betrugen 90 %, die Kathodenschicht war gleichmäßig und silberglänzend; laut Analyse enthielt die Schicht 71.8 % Al und 28.2 % Mg, die Schichtdicke betrug 13 µm.The electrolyte of Example 11 was electrolyzed after replacing the cathode with a new one, also made of tempering steel, at 95-104 ° C. The anodic current densities were set to 0.45 ADm -2 for aluminum and 0.15 ADm -2 for magnesium. The anodic current yields were 90%, the cathode layer was uniform and shiny silver; According to the analysis, the layer contained 71.8% Al and 28.2% Mg, the layer thickness was 13 µm.

    Beispiel 13Example 13

    Der Elektrolyt des Beispiels 12 wurde nach Austausch der Anoden aus Al und Mg gegen zwei Legierungsanoden der Zusammensetzung 75 Gew.-% Al und 25 Gew.-% Mg und nach Einsatz einer neuen cylindrischen Kathode aus Vergütungsstahl 8.8 bei 93 °C elektrolysiert. Während der Elektrolyse rotierte die Kathode langsam zwischen beiden Anoden, die kathodische Stromdichte betrug 0.8 A · dm-2. Die Kathodenschicht war nach Durchgang von 3.5 mF 12 µm dick und war gleichmäßig und mattsilbern.The electrolyte of Example 12 was electrolyzed after replacing the anodes made of Al and Mg with two alloy anodes of the composition 75% by weight Al and 25% by weight Mg and after using a new cylindrical cathode made of tempering steel 8.8 at 93 ° C. During the electrolysis, the cathode slowly rotated between the two anodes, the cathodic current density was 0.8 A · dm -2 . After passing through 3.5 mF, the cathode layer was 12 µm thick and was uniform and matt silver.

    Beispiel 14Example 14

    Beispiel 13 wurde dreimal nach Austausch der Kathode gegen eine unbeschichtete bei 92 - 100 °C wiederholt. Die jeweiligen Schichtdicken wurden zwischen 10 und 15 µm variiert. Die anodische Stromausbeute betrug über die 4 Versuche für die Legierungsanoden 98.9 %. Example 13 was performed three times after replacing the cathode with an uncoated one repeated at 92 - 100 ° C. The respective layer thicknesses were between 10 and 15 µm varies. The anodic current yield was over the 4th Trials for the alloy anodes 98.9%.

    Beispiel 15Example 15 a) Darstellung von Rb[Al(Et)4]a) Representation of Rb [Al (Et) 4 ]

    33,65g (0,203mol) Na[Al(Et)4] wurden mit 37,3g (0,405mol) Toluol auf 90°C Badtemperatur erhitzt. Zu der Suspension gibt man in 2 Portionen 24,4g (0,202mol) trockenes RbCl. Nach Zugabe rührt man bei 90°C 14h nach. Die schwachgelb bis orange gefärbte Lösung läßt man auf 70°C abkühlen und trennt die Suspension durch Filtrieren durch eine Glasfaserhülse, man wäscht mit ca. 30g Toluol nach. Das Filtrat ist eine klare, schwach rostrot gefärbte Lösung und enthält Rb : Na im molaren Verhältnis 0,93 : 0,07. Die Analysen entsprechen einer Zusammensetzung von M[Al(Et)4] mit 3,63Toluol (M= Rb + Na). Die spezifische Leitfähigkeit beträgt bei 95°C 12,9mS·cm-1. 33.65g (0.203mol) Na [Al (Et) 4 ] were heated to 90 ° C bath temperature with 37.3g (0.405mol) toluene. 24.4 g (0.202 mol) of dry RbCl are added to the suspension in two portions. After the addition, the mixture is stirred at 90 ° C. for 14 hours. The pale yellow to orange colored solution is allowed to cool to 70 ° C. and the suspension is separated by filtering through a glass fiber tube, washing with about 30 g of toluene. The filtrate is a clear, slightly rust-red colored solution and contains Rb: Na in a molar ratio of 0.93: 0.07. The analyzes correspond to a composition of M [Al (Et) 4 ] with 3.63 toluene (M = Rb + Na). The specific conductivity is 12.9mS · cm -1 at 95 ° C.

    b) Beispiel eines Rb[Al(Et)4] -Elektrolyten mit Al(Et)3 in Toluolb) Example of an Rb [Al (Et) 4 ] electrolyte with Al (Et) 3 in toluene

    Ein Elektrolyt der Zusammensetzung M[Al(Et)4] / 2,17Al(Et)3 / 4Toluol (M = 93mol%Rb, 7mol%Na) und einer spezifischen Leitfähigkeit von 8,7mS·cm-1 bei 95°C wurde mit zwischen zwei AlMg25-Legierungsanoden befindlicher rotierender Stahlschraube (8.8) als Kathode bei 90-95°C elektrolysiert. Die Stromdichte wurde bezüglich der Stahlkathode auf 0.8A·dm-2 eingestellt. Die Strommenge betrug in insgesamt 6 Einsätzen zwischen 3,5 und 6,0 mF.
    Die Kathodenschichten waren anfänglich gleichmäßig, hellmatt, allmählich jedoch gleichmäßig seidig silberglänzend und betrugen zwischen 30mg und 50mg. Die berechneten Schichtdicken lagen zwischen 12 bis 20mm. Die anodische Stromausbeute betrug über 6 Versuche 100%. Die anfängliche Zusammensetzung der Schicht mit einem frischen Elektrolyten lag bei 90.96%Al und 9,04%Mg. Im Verlauf der weiteren Einsätze konditionierte sich das System bis zu einer Schichtzusammensetzung von 75,02%AI und 24,98%Mg.    An electrolyte of the composition M [Al (Et) 4 ] / 2.17Al (Et) 3/4 toluene (M = 93mol% Rb, 7mol% Na) and a specific conductivity of 8.7mS · cm -1 at 95 ° C was Electrolyzed with a rotating steel screw (8.8) between two AlMg25 alloy anodes as the cathode at 90-95 ° C. The current density was set to 0.8A · dm -2 with respect to the steel cathode. The total amount of electricity in 6 operations was between 3.5 and 6.0 mF.
    The cathode layers were initially uniform, light matt, but gradually became evenly silky silvery and were between 30 mg and 50 mg. The calculated layer thicknesses were between 12 and 20mm. The anodic current yield was 100% over 6 tests. The initial composition of the layer with a fresh electrolyte was 90.96% Al and 9.04% Mg. In the course of further operations, the system conditioned itself to a layer composition of 75.02% Al and 24.98% Mg.

    c) Beispiel eines Rb[Al(Et)4] -Elektrolyten mit Al(n-C3H7)3 in Toluolc) Example of an Rb [Al (Et) 4 ] electrolyte with Al (nC 3 H 7 ) 3 in toluene

    Ein Elektrolyt der Zusammensetzung M[Al(Et)4] / 1,98Al(n-C3H7]3 / 4,24Toluol (M = 93mol% Rb, 7mol% Na) und einer spezifischen Leitfähigkeit von 4,6mS·cm-1 bei 95°C wurde mit zwischen zwei AlMg25-Legierungsanoden befindlicher rotierender Stahlschraube (8.8) als Kathode bei 90-95°C eiektrolysiert. Die Stromdichte wurde bezüglich der Stahlkathode zwischen 0,2 bis 0,6A·dm-2 eingestellt. Die Strommenge betrug zwischen 3,5 und 7,0mF. Die Kathodenschichten waren in allen Stromdichtebereichen optisch ungleichmäßig, dunkel und matt und betrugen zwischen 27 und 52mg, die berechneten Schichtdicken lagen zwischen 12 und 23µm. Die anodische Stromausbeute betrug über 5 Versuche 98,0%.An electrolyte of the composition M [Al (Et) 4 ] / 1.98Al (nC 3 H 7 ] 3 / 4.24 toluene (M = 93mol% Rb, 7mol% Na) and a specific conductivity of 4.6mS · cm -1 at 95 ° C., the rotating steel screw (8.8) between two AlMg25 alloy anodes was electrolysed as the cathode at 90-95 ° C. The current density with respect to the steel cathode was set between 0.2 to 0.6 A · dm -2 between 3.5 and 7.0 mF. The cathode layers were optically uneven, dark and matt in all current density ranges and were between 27 and 52 mg, the calculated layer thicknesses were between 12 and 23 µm. The anodic current yield was 98.0% over 5 tests.

    Claims (19)

    1. An halide-free electrolyte for the electrolytic deposition of aluminum-magnesium alloys, characterized by containing an organoaluminum mixture essentially consisting of
      either
      alkali tetraalkylaluminate M[AlR4]
      or
      alkali hexaalkylhydridodialuminate M[AlR3-H-AlR3] and alkali tetraalkylaluminate M[AlR4]; and
      trialkylaluminum AlR'3 and a magnesium component;
      wherein
      M = Li, Na, K, Rb or Cs; and
      R, R' = CH3, C2H5, C3H7 or n- or iso-C4H9, wherein R and R' are the same or different.
    2. The electrolyte according to claim 1, wherein said organoaluminum mixture is an ethylorganoaluminum mixture which essentially consists of either
      K[AlEt4] (A) and Na[AlEt4] (B) with a molar ratio of B:A within a range of 0 ≤ B:A ≤ 1:3;
      or
      Na[Et3Al-H-AlEt3] (C) and Na[AlEt4] (D) with a molar ratio of D:C within a range of 1:4 ≤ D:C ≤ 1:1; and
      trialkylaluminum (E).
    3. The electrolyte according to claims 1-2, wherein triethylaluminum AlEt3 is employed as said trialkylaluminum.
    4. The electrolyte according to claims 2-3 without an Na[Et3Al-F-AlEt3] component, wherein the molar ratio of A:B is between 9:1 and 3:1, and the molar ratio of (A+B):E is between 1:0.5 and 1:3.
    5. The electrolyte according to claim 4, wherein the molar ratio of A:B is 4:1.
    6. The electrolyte according to claims 2-3 without a K[AlEt4] component, wherein the molar ratio of D:C is 1:2 and that of D:E is from 1:2 to 1.1.
    7. The electrolyte according to claims 1-3, characterized in that said organoaluminum mixture is dissolved in an aromatic hydrocarbon which is liquid at 20 °C.
    8. The electrolyte according to claims 4, 5 and 7, characterized in that said organoaluminum mixture is dissolved in 2-6 mol of toluene, based on the total amount employed of Na[AlEt4] and K[AlEt4].
    9. The electrolyte according to claims 2, 3, 6 and 7, wherein said organoaluminum mixture is dissolved in 5-7 mol of toluene, based on the Na[AlEt4] employed.
    10. The electrolyte according to claims 1-3 and 7, characterized in that the organoaluminum components are dissolved in a mixture of a liquid aromatic hydrocarbon with an aliphatic mono-, di- or polybasic ether R"OR"' (R" = R''' = alkyl; or R" = alkyl, R''' = CH2OR"), and the molar ratio of AlR3:R"OR"' is between 0.5 and 1.0.
    11. The electrolyte according to claim 10, characterized in that the aliphatic ether is dimethoxyethane CH3OCH2CH2OCH3, the aromatic hydrocarbon is toluene, and the molar ratio of triethylaluminum:dimethoxyethane is from 0.8 to 0.9.
    12. A method for the electrolytic deposition of aluminum-magnesium alloys on electrically conductive materials, characterized in that an electrolyte according to claims 1 to 11 is employed, and aluminum and magnesium anodes or aluminum-magnesium alloy anodes are used as anodes, the composition of the anode alloy corresponding to that of the desired alloy coating.
    13. The method according to claim 12, characterized by being performed within a temperature range of from 80 to 105 °C.
    14. The method according to claims 12-13, wherein an alloy coating with an aluminum/magnesium ratio of between 95:5 and 5:95 is produced.
    15. The method according to claims 12 to 14, wherein the magnesium concentration in the electrolyte necessary for the sought magnesium content of the alloy coating is adjusted by a preliminary electrolysis or by a single addition of Mg[AlEt4]2 at the beginning of the electrolysis.
    16. The method according to claim 12 for reducing or avoiding contact corrosion on magnesium constructional parts, characterized in that Mg incorporation rates of from 5 to 50% by weight result in the formation of intermetallic phases within the alloy layer.
    17. The method according to claim 12 for avoiding H2-induced environmental stress cracking, wherein high strength steel parts having a tensile strength of > 1000 MPa are employed as electrically conductive materials.
    18. The method according to claim 16, wherein said magnesium constructional parts are constructional parts of the automobile industry in the gear, engine and car body fields.
    19. The electrolyte according to claim 1, wherein said magnesium component is adjusted to the desired magnesium concentration in the electrolyte by preliminary electrolysis using Al-Mg anodes or by a single addition of Mg[AlR4]2.
    EP99962174A 1998-12-01 1999-11-27 Aluminium organic electrolytes and method for electrolytic coating with aluminium or aluminium-magnesium-alloys Expired - Lifetime EP1141447B1 (en)

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