EP1518945A1 - Electrolyte for the galvanic deposition of aluminium magnesium alloys - Google Patents

Abstract

Electrolyte for electroplating with aluminum-magnesium alloys contains organo-aluminum complex(es) (I) and a magnesium alkyl compound (II), where (I) comprises sodium, potassium, rubidium or cesium-aluminum tetraalkyl with 1-10, preferably 1-4 carbon alkyl groups. Electrolyte for electroplating with aluminum-magnesium alloys contains organo-aluminum complex(es) of formula MAl(R) 4 (I) and a magnesium (Mg) alkyl compound Mg (R 1>) x(R 2>) y (II); M : Na, K, Rb or Cs; R : 1-10, preferably 1-4 C alkyl; and R 1>, R 2>1-20C, preferably 2-10C alkyl group. Independent claims are also included for the following: (1) preparation of the electrolyte; (2) electrolysis kit for electroplating with AlMg alloys.

Description

The invention relates to an electrolyte for electrodeposition of aluminum-magnesium alloys containing at least one organoaluminum complex compound and a magnesium alkyl compound. Further objects of the invention are a process for the preparation of the electrolyte, a coating process, the use of the electrolyte and a Electrolysis kit.

Magnesium-organoaluminum complex compounds have been around recently for the electrolytic deposition of aluminum-magnesium alloys used. This is described in WO 00/32847 A1. The interest in electrolytic Coatings of metal workpieces with aluminum-magnesium alloys has because of the excellent corrosion protection by the aluminum-magnesium layers and their ecological safety greatly increased. Therefore, the galvanic coating with magnesium aluminum organic Electrolytes that are at temperatures in the range of 60 - 150 ° C in closed systems, has achieved great technical importance.

In WO 00/32847 A1 complex compounds of the general type MAIR ₄ and mixtures thereof in combination with aluminum-alkylene AIR _{3 have been} proposed as particularly suitable electrolytes. These are used in the form o their solutions in liquid, aromatic hydrocarbons. M can be an alkali metal such as sodium, potassium, rubidium and cesium, R are alkyl radicals having preferably one, two or four carbon atoms.

However, the application of these electrolyte systems has significant disadvantages. The hitherto known systems are characterized by the fact that the required magnesium-organic complex compounds are initially not available in the electrolyte and must be generated in an electrochemically complex manner only when the electrolyte is used in situ. Thus, ready-to-use starting mixtures contain only organic aluminum compounds but no magnesium compounds. Typical compositions of such starting mixtures contain, for example, molar ratios of 1: 0.1 to 0.1: 1 M ¹ AIR ₄ to M ² AIR ₄ , where M ^{1 is} not equal to M ² with Na, K, Rb, Cs, in particular Na, K is. The molar ratios of all components are AlR ₃ to (M ¹ AIR ₄ + M ² AIR ₄ ): aromatic hydrocarbon = 1: 0.1: 1 to 1: 2: 10, in particular 1: 1: 3 to 1: 1: 5 ,

In these electrolytes is in the suitable for coating E-lektrolyse cells First, the above-mentioned magnesium-free starting electrolyte filled. Then, by applying a current by means of separate aluminum and magnesium anodes or an aluminum-magnesium mixing electrode the required organic magnesium complex is generated in situ electrochemically until the concentration of magnesium complex in the electrolyte necessary for coating is reached.

In addition, until this time, thus reaching the necessary concentration of magnesium complex, already a deposition of aluminum-magnesium layers in the system, which is undesirable since they are has wrong compositions of Al and Mg. Therefore, it is necessary Dummy sheets for collecting the deposited aluminum-magnesium layers to install in the system. These deposits take place on dummy sheets, until it reaches the required concentration of aluminum-magnesium complexes becomes. Then the dummy sheets are removed and the desired ones Layers with the desired aluminum-magnesium composition, such as for example Al: Mg = 75: 25 mol%, deposited on the substrate. The dummy sheets must either be discarded or cleaned consuming for further use become.

From the above description is readily apparent that this process is very expensive and requires a long lead time until obtained the corresponding desired aluminum-magnesium concentrations become. Furthermore occurs as an additional step assembly, disassembly and cleaning the dummy sheets used. The in WO 00/32847 A1 Therefore, electrolyte solutions identified as particularly effective can only be used about the above-described electrochemical generation of magnesium-organic Complexes in one of the actual coating preceding Conditioning phase can be used with all the disadvantages mentioned above.

It is also known from the prior art of WO 00/32847 A1, to add a corresponding magnesium compound directly to the electrolyte in order to omit the above-mentioned conditioning phase can. Here, a magnesium-aluminum-alkyl complex Mg [Al (Et) ₄ ] _{2 is used} in the electrolyte. The disadvantage of this method is that although it is feasible on a laboratory scale but can not be carried out industrially, because this complex is not technically available and is very expensive and expensive to produce.

A suitable electrolyte for a large-scale process for Coating substrates with Al-Mg alloys that are economical and effective can be performed is not yet known. The further development of electrolytes for the electrodeposition of aluminum-magnesium alloys is of great technical significance and high economic and ecological interest.

The technical object of the invention is therefore an electrolyte to make it as simple, efficient and cost-effective as possible can be produced, which is a commercial introduction of the aluminum-magnesium coating process allows and the above conditioning phase no longer necessary for the formation of organic Mg complexes power.

This technical object is achieved by an electrolyte for the electrodeposition of aluminum-magnesium alloys containing at least one aluminum-organic complex compound of the formula MAIR ₄ or mixtures thereof and a magnesium alkyl compound, where M is sodium, potassium, rubidium or cesium, and R a C ₁ -C ₁₀ alkyl group, preferably a C ₁ -C ₄ alkyl group. In a particularly preferred embodiment, the electrolyte additionally contains an aluminum trialkyl compound.

It is particularly preferred to use an electrolyte containing AIR ₃ , M ¹ AIR ₄ , M ² AIR ₄ and Mg (R ¹ ) _x (R ² ) _y , where M ¹ and M ^{2 are} unequal and Na, K, Rb or Cs, R is a C ₁ to C ₁₀ alkyl group, preferably C ₁ to C ₄ alkyl group, R ¹ and R ^{2 are} independently a C ₁ to C ₂₀ , preferably a C ₂ to C ₁₀ alkyl group and x = 0 to Is 2 and y = 0 to 2 and x + y = 2.

It has surprisingly been found that the inventive Electrolyte for coating materials with aluminum-magnesium alloys can be used without the in situ generation of magnesium-organic Complexes in a time and cost intensive conditioning phase is necessary before the actual coating process.

Preferably, the magnesium alkyl compound is in one Amount of 0.01 to 10 mol%, preferably 0.1 to 1 mol% based on the Aluminum complex contained in the electrolyte. Particularly preferred magnesium alkyl compounds, which are used in the electrolyte are selected from the group MgButyl1,5Octyl0.5, MgButyl1, Oethyl1, 0, Mgsec-Bu1, OnButyl1, 0 or Mixtures thereof.

The aluminum-organic complex compound and the magnesium alkyl compound may preferably be in an organic solvent. The organic solvent is more preferably an aromatic solvent, where solvents such as benzene, toluene or xylene or mixtures the same can be used.

The above-mentioned magnesium alkyl compounds have the advantage that they are industrially available and can be prepared simply and inexpensively in comparison to the abovementioned magnesium aluminum-ethyl complexes Mg [Al (Et)) ₄ ] ₂ The preparation of the electrolyte is carried out according to the following steps. First, the aluminum-organic complex compound of the formula MAIR ₄ or a mixture thereof, optionally in combination with aluminum trialkyl submitted. There then takes place the addition of a magnesium-alkyl compound as described above. M and R have the same meaning as described above. The addition of the magnesium-alkyl compounds in the preparation of the electrolyte has the advantage that the necessary concentration of magnesium and aluminum can be adjusted directly, so that can be completely dispensed with the above-mentioned conditioning process. Furthermore, it is also possible to add magnesium-alkyl compounds during the coating process in order to maintain the appropriate magnesium concentration desired and necessary for the coating.

In a particularly preferred embodiment, the magnesium-alkyl compound is a mixed magnesium-alkyl compound of the formula Mg (R ¹ ) _x (R ² ) _y , wherein R ¹ and R ² independently of one another are C ₁ -C ₂₀ , preferably one C ₂ -C ₁₀ alkyl group and x = 0 to 2 and y = 0 to 2 and x + y = 2. The magnesium-alkyl compounds are added dissolved in a hydrocarbon in a particularly preferred embodiment and the aluminum-alkyl complexes are presented dissolved in an aromatic hydrocarbon. The hydrocarbon for the aluminum compound is selected from the group consisting of i-pentane, n-pentane, hexane, n-hexane, heptane, n-heptane, toluene and xylene.

With the electrolyte according to the invention, it is possible in one Operation Aluminum-magnesium layers of different concentration sequences of aluminum and magnesium by simple and free choice of the amount of addition of organomagnesium compounds. Here is the corresponding concentration of aluminum-magnesium over the added amount of organomagnesium compounds. The inventive Electrolyte also has the advantage of good conductivity and throwing power.

The electrolyte according to the invention makes it possible with indifferent anodes to work in the case of the coating of geometrically complicated shaped Parts are used. Indifferent electrodes are those that are in themselves Do not dissolve during the coating process, so not from AI or Mg or their Alloys exist. When coating with indifferent electrodes must therefore Mg-organic compounds and Al-organic compounds in the electrolyte solution be dosed. In doing so, the corresponding concentration of aluminum-magnesium about the addition amount of organomagnesium compounds and organoaluminum compounds. Working with indifferent anodes was in the prior art in situ generation excluded from magnesium-organic complexes in principle, as well as the production of layers of various aluminum-magnesium compositions in one operation. This is also after the above described in situ process with a conditioning step for the preparation the magnesium concentration in the electrolyte is not possible.

a) die aluminium-organischen oben beschriebenen Komplexverbindungen, bzw. Aluminium-Alkyl-Verbindungen der Ansprüche 1 - 3 und 1,3,5,6 sowie

b) eine Magnesium-Alkylverbindung gemäß den Ansprüche 1, 3, 5, 6.

Another object of the invention is an electrolysis kit for the electrodeposition of aluminum-magnesium alloys on electrically conductive materials or electrically conductive layers, comprising:

a) the aluminum-organic complex compounds described above, or aluminum-alkyl compounds of claims 1-3 and 1,3,5,6 and

b) a magnesium alkyl compound according to claims 1, 3, 5, 6.

In a preferred embodiment, the compounds a) and b) dissolved in an organic solvent.

Another object of the invention is a method for coating of electrically conductive materials or layers of aluminum-magnesium alloys with the electrolyte according to claims 1-9, wherein during the coating phase, the magnesium alkyl compound according to to the claims 1, 3, 5 and 6 in the desired amount is added to a desired concentration of magnesium to aluminum to obtain or maintain

Another object of the invention is the use of the invention Electrolytes for the production of layers of aluminum alloys on electrically conductive materials or electrically conductive layers.

The following examples are intended to explain the invention in more detail:

example 1 Use of MgButyl _1.5 Octyl _0.5 , 20% in heptane (product BOMAG® from Crompton)

The entire implementation of the reaction was carried out under protective gas argon

1st step: The BOMAG® / heptane solution was removed after condensation of heptane adjusted by means of toluene to a level of 0.32 mmol / g.

2nd step: 55.4 g of an electrolyte of the following composition: 0.8 K [Al (Et) ₄ ] + 0.2 Na [Al (Et) ₄ ] + 1.17 Al (Et) ₃ + 3.85 Toluene was treated with 2.85 g of BOMAG / toluene solution (about 1.0 mol% based on the electrolyte formulation).

There were obtained about 58 g of an electrolyte.

coating test

Terms and Conditions:

All deposition experiments were carried out under standard conditions. The magnesium component was pipetted directly to the electrolyte. Anodenmateriel: 2 alloy electrodes AIMg25, 55 x 10 x 5mm cathode Hexagon bolt 8.8, M8 x 25

Cathode pretreatment:

Degreasing, descaling in an ultrasonic bath with 8% HCl, H ₂ O washing, vacuum drying, argon storage. Immersion depth cathode: complete Cathode rotation: 60U / min Distance to the anode: 10mm Effective cathode surface: about 10cm ² agitation: 2cm magnet in glass jacket, 250U / min bath temperature: 94 - 98 ° C

The deposition was started at a current density of 0.05A / dm ² . After a few minutes, a light covering on the parts to be coated can be seen. The current density was gradually increased to 3.0A / dm ² . The deposition was terminated after a current of 1.499mF corresponding to a layer thickness of 5μ. The layer is bright and silvery. RF analysis of the layer: 26.79% by weight Mg, 73.21% by weight

Example 2 Use of Mgethyl _1.0 butyl _1.0 , 20% in heptane (BEM, AkzoNobel)

The reaction was carried out under protective gas argon.

1st step: The BEM / heptane solution was after condensation of the Heptanes adjusted by means of toluene to a level of 0.41 mmol / g.

2nd step: 60.6 g of an electrolyte of the following composition: 0.8 K [Al (Et) ₄ ] + 0.2 Na [Al (Et) ₄ ] +1.17 Al (Et) ₃ + 3.85 Toluene was mixed with 2.0 ml of BEM / toluene solution (about 0.9 mol% based on the electrolyte formulation). There were obtained about 62 g of an electrolyte.

Coating Test:

The deposition conditions are as in Example 1. The deposition was started directly at a current density of 2.0 A / dm ² and was not changed throughout the electrolysis. There was an immediate bright deposition of Al / Mg. The deposition was terminated after a current of 3.38 mF corresponding to a layer thickness of 11μ. This gives an excellent, very uniform, silvery layer. without recognizable defects.

RF analysis of the layer: 26.78% Mg, 73.22 wt. Al

Example 3 Use of Mgethyl _1.0 butyl _1.0 , 20% in iso-pentane (BEM from Albemarle)

The reaction was carried out under argon as a protective gas.

1st step: The BEM / isopentane solution is added to a content of 1.85 mmol / g Mg component used without further pretreatment.

2nd step: 70.04 g of an electrolyte of the following composition 0.85 K [Al (Et) ₄ ] + 0.15 Na [Al (Et) ₄ ] + 1.08 Al (Et) ₃ + 3.15 toluene were added 0.5 g of BEM / isopentane solution (about 0.8 mol% based on electrolyte formulation).

coating test

The deposition conditions are as described in Example 1. The deposition took place at a current density of 1.0 to 3.0 A / dm ² . The deposition was terminated after a current of 6.8 mF corresponding to a layer thickness of 20 μ. This gives a very uniform, silvery layer.

RF analysis of the layer: 41.4% Mg, 58.9%. AI Comparative Example 1 Use of electrolytes from the company Albemarle for Al-Mg deposition, however without direct addition of Mg-alkyl solution (conditioning electrolyte).

65.0 g of an electrolyte having the following composition was used: 0.8 K [Al (Et) ₄ ] + 0.2 Na [Al (Et) ₄ ] + 1.17Al (Et) ₃ + 3.85 toluene for Al-Mg deposition with preparatory conditioning under the general conditions, as described above, but without the prior addition of Mg-alkyl solution used so that, as necessary according to the prior art, the Mg complex compound in a conditioning phase first produced electrochemically must be before the electrolyte is ready for the deposition of Al-Mg alloys.

1. Conditioning step: Starting with a starting current density of 0.05 A / dm ^2, electrolyzing was carried out with increasing current density up to the maximum possible value of 1.0 A / dm ² . After a current volume of 7.20 mF, a matte, gray coating is present with poor scattering power.

2nd conditioning step: After replacing the cathode was further conditioned at 1.0 to 1.2 A / dm ² . After an amount of electricity of 7.24 mF, with only slightly improved scattering power, a clearly brightened, in part weak, glossy layer is obtained.

3. Conditioning step: Again, after renewing the cathode, a clear, glossy coating was obtained with significantly increased allowable maximum current density of 1.23 over 1.5 to 2.0 A / dm ² , with significantly improved scattering. The amount of electricity used was 4.96 mF.

4. Conditioning step: Upon reaching the final condition, a glossy coating is obtained using a current density of 3.0 A / dm ² with unchanged throwing power compared to step 3. The amount of electricity is 3.73 mF.

The electrolyte is conditioned only after this process and operational.

Claims (20)

An electrolyte for the electrodeposition of aluminum-magnesium alloys containing at least one organoaluminum complex compound of the formula MAIR ₄ or mixtures thereof and a magnesium alkyl compound, where M is Na, K, Rb or Cs and R is a C ₁ to C ₁₀ alkyl group, preferably C ₁ to C ₄ Alkygruppe means. Electrolyte according to claim 2, characterized in that it additionally contains aluminum trialkyl. An electrolyte according to claim 1 or 2, characterized in that it contains AIR ₃ , M ¹ AlR ₄ , M ² AIR ₄ and Mg (R ¹ ) _x (R ² ) _y , wherein M ¹ and M ^{2 are} unequal and Na, K , Rb or Cs, R is a C ₁ to C ₁₀ alkyl group, preferably C ₁ to C ₄ alkyl group, R ¹ and R ^{2 are} independently a C ₁ to C ₂₀ , preferably a C ₂ to C ₁₀ alkyl group and x = 0 to 2 and y = 0 to 2 and x + y = 2. An electrolyte according to one or more of claims 1 to 3, characterized in that the magnesium alkyl compound is contained in an amount of 0.01 to 10 mol%, preferably 0.1 to 1 mol%, based on the aluminum complex. An electrolyte according to one or more of claims 1 to 4, characterized in that the magnesium alkyl compound is selected from the group MgButyl _1.5 Octyl _0.5 , MgButyl _1.0 ethyl _1.0 , MgSc-Bu _1.0 n-butyl _{1 , 0} or mixtures thereof. Electrolyte according to one or more of claims 1 to 5, characterized in that it contains an organic solvent. Electrolyte according to claim 6, characterized in that the organic solvent is an aromatic solvent. An electrolyte according to claim 7, characterized in that the aromatic solvent is benzene, toluene or xylene or a mixture thereof. Process for the preparation of the electrolyte according to claims 1 to 8, characterized by the following steps: Presenting an organoaluminum complex compound of formula MAIR ₄ or a mixture thereof, optionally in combination with aluminum trialky, Addition of a magnesium alkyl compound, where M is Na, K, Rb or Cs and R is a C ₁ to C ₁₀ alkyl group, preferably C ₁ to C ₄ alkyl group. A method according to claim 9, characterized in that the organoaluminum complex compound is a mixture of M ¹ AIR ₄ and M ² AIR ₄ , wherein M ¹ and M ^{2 are} different, Na, K, Rb or Cs and R is a C ₁ to C ₁₀ alkyl group, preferably a C ₁ to C ₄ alkyl group. Process according to Claim 9, characterized in that the magnesium alkyl compound is Mg (R ¹ ) _x (R ² ) _y , where R ¹ and R ² independently of one another denote a C ₁ to C ₂₀ , preferably a C ₂ to C ₁₀ alkyl group and x = 0 to 2 and y = 0 to 2 and x + y = 2. Method according to one or more of claims 9 to 11, characterized in that the magnesium alkyl compound is added dissolved in a hydrocarbon. Method according to one or more of claims 9 to 11, characterized in that the aluminum alkyl complex is presented dissolved in aromatic hydrocarbon. A method according to claim 12, characterized in that the hydrocarbon is a saturated or unsaturated hydrocarbon. A method according to claim 14, characterized in that the hydrocarbon is selected from the group i-pentane, n-pentane, hexane, n-hexane, heptane, n-heptane, toluene, xylene. Electrolyte for the production of layers of aluminum-magnesium alloys on electrically conductive materials or electrically conductive Layers producible by the process according to claims 9 to 15. Process for coating electrically conductive materials or layers with aluminum-magnesium alloys with the electrolyte according to the Claims 1 to 8, wherein during the coating, the magnesium alkyl compound is added. Use of the electrolyte according to claims 1 to 8 and 16 for the preparation of layers of aluminum-magnesium alloys on electrically conductive Materials or layers. Electrolysis kit for the electrodeposition of aluminum-magnesium alloys on electrically conductive materials or layers containing (A) the organoaluminum complex compounds or aluminum alkyl compounds of claims 1 to 3 (b) a magnesium alkyl compound according to claims 1, 3, 5. Electrolysis kit according to claim 19, characterized in that the compounds (a) and (b) are present in an organic solvent.