U.S. patent application number 10/573519 was filed with the patent office on 2007-05-17 for electrolyte for the galvanic deposition of aluminum-magnesium alloys.
Invention is credited to Richard Lisowsky, Klaus-Dieter Mehler.
Application Number | 20070108061 10/573519 |
Document ID | / |
Family ID | 34178513 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070108061 |
Kind Code |
A1 |
Lisowsky; Richard ; et
al. |
May 17, 2007 |
Electrolyte for the galvanic deposition of aluminum-magnesium
alloys
Abstract
The invention relates to an electrolyte for the galvanic
deposition of aluminum-magnesium alloys, which includes at least
one aluminum-organic complex compound of the formula MAIR4 or
mixtures thereof and a magnesium alkyl compound, wherein M
represents Na, K, Rb or Cs and R represents a C1 to C10 alkyl
group, preferably a C1 to C4 alky group. The invention also relates
to a method for producing an electrolyte, to a coating method, the
use of the electrolyte and to an electrolysis kit.
Inventors: |
Lisowsky; Richard; (Kamen,
DE) ; Mehler; Klaus-Dieter; (Mulheim an der Ruhr,
DE) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
34178513 |
Appl. No.: |
10/573519 |
Filed: |
September 9, 2004 |
PCT Filed: |
September 9, 2004 |
PCT NO: |
PCT/EP04/52113 |
371 Date: |
January 31, 2007 |
Current U.S.
Class: |
205/238 ;
252/62.2 |
Current CPC
Class: |
C25D 3/56 20130101; C25D
3/42 20130101 |
Class at
Publication: |
205/238 ;
252/062.2 |
International
Class: |
C25D 3/56 20060101
C25D003/56 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2003 |
EP |
03021877.0 |
Claims
1. An electrolyte for the galvanic deposition of aluminum-magnesium
alloys, containing at least one organoaluminum complex compound of
formula MAlR.sub.4 or mixtures thereof and an alkylmagnesium
compound, wherein M represents Na, K, Rb or Cs, and R represents a
C.sub.1-C.sub.10 alkyl group, preferably a C.sub.1-C.sub.4 alkyl
group.
2. The electrolyte according to claim 1, characterized in that the
electrolyte additionally includes trialkylaluminum.
3. The electrolyte according to claim 1 or 2, characterized in that
the electrolyte includes AlR.sub.3, M.sup.1AlR.sub.4,
M.sup.2AlR.sub.4 and Mg(R.sup.1).sub.x(R.sup.2).sub.y, wherein
M.sup.1 and M.sup.2 are different from each other, representing Na,
K, Rb or Cs, R represents a C.sub.1-C.sub.10 alkyl group,
preferably a C.sub.1-C.sub.4 alkyl group, R.sup.1 and R.sup.2
independently represent a C.sub.1-C.sub.20, preferably a
C.sub.2-C.sub.10 alkyl group, and x=0 to 2, and y=0 to 2, and
x+y=2.
4. The electrolyte according to one or more of claims 1 to 3,
characterized in that the alkylmagnesium compound is included in an
amount of from 0.01 to 10 mole-%, preferably from 0.1 to 1 mole-%,
relative to the aluminum complex.
5. The electrolyte according to one or more of claims 1 to 4,
characterized in that the alkylmagnesium compound is selected from
the group of Mgbutyl.sub.1.5octyl.sub.0.5,
Mgbutyl.sub.1.0ethyl.sub.1.0, Mgsec-butyl.sub.1.0n-butyl.sub.1.0 or
mixtures thereof.
6. The electrolyte according to one or more of claims 1 to 5,
characterized in that the electrolyte includes an organic
solvent.
7. The electrolyte according to claim 6, characterized in that the
organic solvent is an aromatic solvent.
8. The electrolyte according to claim 7, characterized in that the
aromatic solvent is benzene, toluene or xylene or a mixture
thereof.
9. A method for the production of the electrolyte according to
claims 1 to 8, characterized by the following steps: supplying an
organoaluminum complex compound of formula MAlR.sub.4 or a mixture
thereof, optionally in combination with trialkylaluminum, addition
of an alkylmagnesium compound, wherein M represents Na, K, Rb or
Cs, and R represents a C.sub.1-C.sub.10 alkyl group, preferably a
C.sub.1-C.sub.4 alkyl group.
10. The method according to claim 9, characterized in that the
organoaluminum complex compound is a mixture of M.sup.1AlR.sub.4
and M.sup.2AlR.sub.4, wherein M.sup.1 and M.sup.2 are different
from each other, representing Na, K, Rb or Cs, R represents a
C.sub.1-C.sub.10 alkyl group, preferably a C.sub.1-C.sub.4 alkyl
group.
11. The method according to claim 9, characterized in that the
alkylmagnesium compound is Mg(R.sup.1).sub.x(R.sup.2).sub.y,
wherein R.sup.1 and R.sup.2 independently represent a
C.sub.1-C.sub.20, preferably a C.sub.2-C.sub.10 alkyl group, and
x=0 to 2, and y=0 to 2, and x+y=2.
12. The method according to one or more of claims 9 to 11,
characterized in that the alkylmagnesium compound is added
dissolved in a hydrocarbon.
13. The method according to one or more of claims 9 to 11,
characterized in that the alkylaluminum complex is supplied
dissolved in an aromatic hydrocarbon.
14. The method according to claim 12, characterized in that the
hydrocarbon is a saturated or unsaturated hydrocarbon.
15. The method according to claim 14, characterized in that the
hydrocarbon is selected from the group of i-pentane, n-pentane,
hexane, n-hexane, heptane, n-heptane, toluene, xylene.
16. An electrolyte for the production of aluminum-magnesium alloys
on electrically conducting materials or electrically conducting
layers, which can be produced according to the method of claims 9
to 15.
17. A method of coating electrically conducting materials or layers
with aluminum-magnesium alloys using the electrolyte in accordance
with claims 1 to 8, in which method the alkylmagnesium compound is
metered during coating.
18. Use of the electrolyte according to claims 1 to 8 and 16 for
the production of layers of aluminum-magnesium alloys on
electrically conducting materials or layers.
19. An electrolysis kit for the galvanic deposition of
aluminum-magnesium alloys on electrically conducting materials or
layers, including: (a) the organoaluminum complex compounds or
alkylaluminum compounds of claims 1 to 3; and (b) an alkylmagnesium
compound in accordance with claims 1, 3, 5.
20. The electrolysis kit according to claim 19, characterized in
that the compounds (a) and (b) are present in an organic
solvent.
21.-26. (canceled)
Description
[0001] 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.
[0002] Recently, 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. There has
been rapidly increasing interest in 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.degree. C. in closed systems has gained major technical
importance.
[0003] WO 00/32847 A1 suggests complex compounds of the general
type MAlR.sub.4 and mixtures thereof in combination with aluminum
alkyls AlR.sub.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.
[0004] However, the use of such electrolyte systems has crucial
disadvantages. The systems known to date involve the characteristic
feature that, initially, the required organomagnesium complex
compounds are not present in the electrolyte, and complex in situ
electrochemical production thereof is required at that point in
time when it comes to using the electrolyte. Thus, ready-for-use
starting mixtures exclusively contain organic aluminum compounds,
but no magnesium compounds. For example, typical compositions of
such starting mixtures include molar ratios of from 1:0.1 to 0.1:1
of M.sup.1AlR.sub.4 to M.sup.2AlR.sub.4, wherein M.sup.1 is
different from M.sup.2 and is Na, K, Rb, Cs, particularly Na, K.
The molar ratios of all components
AlR.sub.3/(M.sup.1AlR.sub.4+M.sup.2AlR.sub.4)/aromatic hydrocarbon
ranges from 1:0.1:1 to 1:2:10, particularly from 1:1:3 to
1:1:5.
[0005] In such electrolytes 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.
[0006] Moreover, 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. For this reason, dummy metal sheets must be placed in
the system in order to collect the deposited aluminum-magnesium
layers. Deposition on dummy metal sheets proceeds until the
required concentration of aluminum-magnesium complexes is reached.
Thereafter, the dummy metal sheets are removed, and the desired
layers having the desired aluminum-magnesium composition, e.g.
Al:Mg=75:25 mole-%, are deposited on the substrate. The dummy metal
sheets must be either discarded or subjected to complex cleaning
for further use.
[0007] From the description given above, it can easily be seen that
this process is highly complex, requiring a long pre-run time until
the corresponding desired aluminum-magnesium concentrations are
obtained. Furthermore, mounting, removing and cleaning the dummy
metal sheets used arises as additional working step. For this
reason, the electrolyte solutions identified as particularly
effective in WO 00/32847 A1 can only be employed via the
above-described electrochemical production of organomagnesium
complexes in a conditioning phase preceding the actual coating,
with all the disadvantages mentioned above.
[0008] Furthermore, direct addition of a corresponding magnesium
compound to the electrolyte is well-known from the WO 00/32847 A1
prior art, allowing to omit the above-mentioned conditioning phase.
Here, a magnesium-aluminum alkyl complex, Mg[Al(Et).sub.4].sub.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.
[0009] Appropriate electrolytes for an industrial process for the
coating of substrates with Al--Mg alloys, which could be carried
out economically and effectively, are not known to date. Further
development of electrolytes for the galvanic deposition of
aluminum-magnesium alloys are of great technical importance and
highly interesting in economical and ecological terms.
[0010] 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.
[0011] The above technical object is accomplished by means of an
electrolyte for the galvanic deposition of aluminum-magnesium
alloys, containing at least one organoaluminum complex compound of
formula MAlR.sub.4 or mixtures thereof and an alkylmagnesium
compound, in which formula M represents sodium, potassium, rubidium
or cesium, and R represents a C.sub.1-C.sub.10 alkyl group,
preferably a C.sub.1-C.sub.4 alkyl group. In a particularly
preferred embodiment the electrolyte additionally includes a
trialkylaluminum compound.
[0012] In a particularly preferred fashion, an electrolyte is used
which includes AlR.sub.3, M.sup.1AlR.sub.4, M.sup.2AlR.sub.4 and
Mg(R.sup.1).sub.x(R.sup.2).sub.y, wherein M.sup.1 and M.sup.2 are
different from each other, representing Na, K, Rb or Cs, R
represents a C.sub.1-C.sub.10 alkyl group, preferably a
C.sub.1-C.sub.4 alkyl group, R.sup.1 and R.sup.2 independently
represent a C.sub.1-C.sub.20, preferably a C.sub.2-C.sub.10 alkyl
group, and x=0 to 2, and y=0 to 2, and x+y=2.
[0013] Surprisingly, it was found that 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.
[0014] In a preferred fashion 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.sub.1.5octyl.sub.0.5, Mgbutyl.sub.1.0ethyl.sub.1.0,
Mgsec-butyl.sub.1.0n-butyl.sub.1.0 or mixtures thereof.
[0015] The organoaluminum complex compound and the alkylmagnesium
compound can preferably be present in an organic solvent. In a
particularly preferred fashion the organic solvent is an aromatic
solvent, in which case solvents such as benzene, toluene or xylene
or mixtures thereof can be used.
[0016] Compared to the above-mentioned magnesium-aluminum ethyl
complexes Mg[Al(Et).sub.4].sub.2, 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.sub.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.
[0017] In a particularly preferred embodiment the alkylmagnesium
compound is a mixed alkylmagnesium compound of formula
Mg(R.sup.1).sub.x(R.sup.2).sub.y wherein R.sup.1 and R.sup.2
independently represent a C.sub.1-C.sub.20, preferably a
C.sub.2-C.sub.10 alkyl group, and x=0 to 2, and y=0 to 2, and
x+y=2. In a particularly preferred embodiment 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.
[0018] Using the 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
[0019] 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. When coating with indifferent electrodes,
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.
According to the previous state of the art, 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.
[0020] 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: [0021] a) the organoaluminum complex compounds
described above or alkylaluminum compounds of claims 1 to 3 and 1,
3, 5, 6; and [0022] b) an alkylmagnesium compound in accordance
with claims 1, 3, 5, 6.
[0023] In a preferred embodiment the compounds a) and b) are
dissolved in an organic solvent.
[0024] 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.
[0025] 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.
[0026] The invention will be illustrated in more detail with
reference to the examples below.
EXAMPLE 1
Use of Mgbutyl.sub.1.5octyl.sub.0.5, 20% in heptane (product
BOMAG.RTM. from the Company Crompton)
[0027] The entire implementation of the reaction was under argon
protective gas.
[0028] Step 1: Following removal of heptane by condensation, the
BOMAG.RTM./heptane solution was adjusted to a content of 0.32
mmol/g using toluene.
[0029] Step 2: 55.4 g of an electrolyte having the following
composition: 0.8 K[Al(Et).sub.4]+0.2 Na[Al(Et).sub.4]+1.17
Al(Et).sub.3+3.85 toluene was added with 2.85 g of BOMAG/toluene
solution (about 1.0 mole-%, relative to the electrolyte
formulation).
[0030] About 58 g of an electrolyte was obtained.
Coating Test
[0031] General Conditions:
[0032] All deposition tests were performed under standard
conditions. The magnesium component was directly pipetted into the
electrolyte. [0033] Anode material: 2 alloy electrodes, AlMg,
25.55.times.10.times.5 mm [0034] Cathode: hexagonal screw, 8.8,
M8.times.25 [0035] Cathode pretreatment: degreasing, descaling in
ultrasonic bath with 8% HCl, H.sub.2O wash, vacuum drying, storage
under argon [0036] Cathode immersion depth: complete [0037] Cathode
rotation: 60 rpm [0038] Distance to anode: 10 mm [0039] Effective
cathode surface: about 10 cm.sup.2 [0040] Bath agitation: 2 cm
magnet in glass jacket, 250 rpm [0041] Bath temperature:
94-98.degree. C.
[0042] Deposition was started at a current density of 0.05
A/dm.sup.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.sup.2. Deposition was terminated after a current quantity
of 1.499 mF, corresponding to a layer thickness of 5 .mu.m. The
layer is bright and silvery. RF analysis of the layer: 26.79 wt.-%
Mg, 73.21 wt.-% Al
EXAMPLE 2
Use of Mgethyl.sub.1.01butyl.sub.1.0, 20% in heptane (BEM, company
Akzo-Nobel)
[0043] The reaction was effected under argon protective gas.
[0044] Step 1: Following removal of heptane by condensation, the
BEM/heptane solution was adjusted to a content of 0.41 mmol/g using
toluene.
[0045] Step 2: 60.6 g of an electrolyte having the following
composition: 0.8 K[Al(Et).sub.4]+0.2 Na[Al(Et).sub.4]+1.17
Al(Et).sub.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.
Coating Test:
[0046] The deposition conditions were as in Example 1. Deposition
was started directly with a current density of 2.0 A/dm.sup.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 .mu.m. An excellent, highly uniform, silvery layer
with no recognizable flaws was obtained.
[0047] RF analysis of the layer: 26.78 wt.-% Mg, 73.22 wt.-% Al
EXAMPLE 3
Use of Mgethyl.sub.1.0butyl.sub.1.0, 20% in Isopentane (BEM from
the Company Albemarle)
[0048] The reaction was effected under argon as protective gas.
[0049] Step 1: The BEM/isopentane solution with a content of 1.85
mmol/g Mg component is used without further pretreatment.
[0050] Step 2: 70.04 g of an electrolyte having the following
composition: 0.85 K[Al(Et).sub.4]+0.15 Na[Al(Et).sub.4]+1.08
Al(Et).sub.3+3.15 toluene was added with 0.5 g of BEM/isopentane
solution (about 0.8 mole-%, relative to the electrolyte
formulation).
Coating Test
[0051] 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.sup.2. Deposition was terminated after a current quantity of 6.8
mF, corresponding to a layer thickness of 20 .mu.m. A highly
uniform, silvery layer was obtained.
[0052] RF analysis of the layer: 41.4% Mg, 58.9%. Al
COMPARATIVE EXAMPLE 1
Use of Electrolytes from the Company Albemarle for Al--Mg
Deposition, but without Direct Addition of Mg-alkyl Solution
(Conditioning Electrolyte)
[0053] 65.0 g of an electrolyte having the following composition:
0.8 K[Al(Et).sub.4]+0.2 Na[Al(Et).sub.4]+1.17 Al(Et).sub.3+3.85
toluene was used with preparatory conditioning under the general
conditions as described above, but without previous addition of
Mg-alkyl solution, so that, as required in accordance with the
previous state of the art, the Mg complex compound has to be
generated electrochemically in a conditioning phase before the
electrolyte is ready for use in the deposition of Al--Mg
alloys.
[0054] Conditioning step 1: Starting with an initial current
density of 0.05 A/dm.sup.2, electrolysis was effected with the
current density increasing up to the maximum possible value of 1.0
A/dm.sup.2. After a current quantity of 7.20 mF, with poor throwing
power, a dull, gray coating was obtained.
[0055] Conditioning step 2: After replacing the cathode,
conditioning was continued at 1.0 to 1.2A/dm.sup.2. After a current
quantity of 7.24 mF, with scarcely improved throwing power, a
markedly brighter layer faintly lustrous in parts was obtained.
[0056] Conditioning step 3: Again, after replacing the cathode, but
now with a significant increase of the maximum allowable current
density of 1.23 beyond 1.5 and up to 2.0 A/dm.sup.2, a uniform
lustrous coating with significantly improved throwing power was
obtained. The amount of current used was 4.96 mF.
[0057] Conditioning step 4: Reaching the final condition, a
lustrous coating was obtained using a current density of 3.0
A/dm.sup.2, with throwing power unchanged compared to step 3. The
current quantity was 3.73 mF.
[0058] The electrolyte is conditioned and operational only after
this procedure.
* * * * *