CA2272254A1 - Electrolyte for aluminium electroplating - Google Patents
Electrolyte for aluminium electroplating Download PDFInfo
- Publication number
- CA2272254A1 CA2272254A1 CA002272254A CA2272254A CA2272254A1 CA 2272254 A1 CA2272254 A1 CA 2272254A1 CA 002272254 A CA002272254 A CA 002272254A CA 2272254 A CA2272254 A CA 2272254A CA 2272254 A1 CA2272254 A1 CA 2272254A1
- Authority
- CA
- Canada
- Prior art keywords
- aluminum
- electrolyte
- complexes
- lewis base
- formula
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/42—Electroplating: Baths therefor from solutions of light metals
- C25D3/44—Aluminium
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electroplating And Plating Baths Therefor (AREA)
- Conductive Materials (AREA)
- Paints Or Removers (AREA)
- Electroplating Methods And Accessories (AREA)
Abstract
The invention relates to an electrolyte for aluminium electroplating, which contains an organometallic aluminium complex of the formula (I): MF.2A1R3, whereby M stands for Na, K, Rb, Cs and R stands for C1-C4 alkyl group, in a solvent mixture comprising an aromatic or aliphatic hydrocarbon and a Lewis base. The invention further relates to the use of said electrolyte in the manufacture of decorative, corrosion-resistant aluminium coatings.
Description
~, ~, 9708125.DOC
An Electrolyte for the Electrodeposition of Aluminum s The invention relates to an electrolyte for elec-trodepositing aluminum, containing an organometallic alu-minum complex, and to the use of said electrolyte in the production of decorative, corrosion-resistant aluminum coatings.
~o Aluminum can be ele:ctrodeposited from a variety of electrolytes. These electrolytes include, e.g., fused-salt electrolytes and electrolyi~es containing aluminum halides or alkyl aluminum complexes>. For the deposition of alumi-.
is num on an industrial scale,, however, it has been exclusi-vely electrolyte systems based on alkyl aluminum complexes which gained technical importance in recent years. The electrolytic deposition of: aluminum from alkyl aluminum complexes has already been described in the fifties by zo Ziegler and Lehmkuhl. In general, these alkyl aluminum complexes consist of an alkali metal halide salt and a corresponding alkyl aluminum compound at a molar ratio of 1:1. However, they have relatively poor electric conducti-vity.
zs It has later been found that complexes having a molar ratio of 1:2 are formed as well, which complexes contain two moles of alkyl aluminum compound and only one mole of alkali metal halide and have a considerably higher 3o electric conductivity. Thi:> discovery was particularly im-portant for uses involving electrodeposition of aluminum, because a certain minimum conductivity must be present for economic performance of the electrodeposition process.
s5 Initially, electrolyte solutions containing the NaF~~~l:t3 complex dissolved in aromatic hydrocarbons such as toluene or xylene haves exclusively been used in the - . 970B12-6.00C
An Electrolyte for the Electrodeposition of Aluminum s The invention relates to an electrolyte for elec-trodepositing aluminum, containing an organometallic alu-minum complex, and to the use of said electrolyte in the production of decorative, corrosion-resistant aluminum coatings.
~o Aluminum can be ele:ctrodeposited from a variety of electrolytes. These electrolytes include, e.g., fused-salt electrolytes and electrolyi~es containing aluminum halides or alkyl aluminum complexes>. For the deposition of alumi-.
is num on an industrial scale,, however, it has been exclusi-vely electrolyte systems based on alkyl aluminum complexes which gained technical importance in recent years. The electrolytic deposition of: aluminum from alkyl aluminum complexes has already been described in the fifties by zo Ziegler and Lehmkuhl. In general, these alkyl aluminum complexes consist of an alkali metal halide salt and a corresponding alkyl aluminum compound at a molar ratio of 1:1. However, they have relatively poor electric conducti-vity.
zs It has later been found that complexes having a molar ratio of 1:2 are formed as well, which complexes contain two moles of alkyl aluminum compound and only one mole of alkali metal halide and have a considerably higher 3o electric conductivity. Thi:> discovery was particularly im-portant for uses involving electrodeposition of aluminum, because a certain minimum conductivity must be present for economic performance of the electrodeposition process.
s5 Initially, electrolyte solutions containing the NaF~~~l:t3 complex dissolved in aromatic hydrocarbons such as toluene or xylene haves exclusively been used in the - . 970B12-6.00C
electrodeposition of aluminum. The above compound has a vAr,i 1cw melting point, whi <:h is ad-~antageous ~~rhen ~issol-vin, r_ he complex in a solvent. An electrolyte of such a composition involves the major drawback of an exceedingly s poor throwing power. As a result, uniform and complete coating of large parts having complicated shapes with an gles and corners can only be achieved with high input and the additional use of auxiliary anodes. It is a costly process with a high technical input which does not allow io economic operation.
However, other alkyl aluminum complexes have also been used. Amongst these are, e.g., electrolytes including aluminum complexes such as lKF~2AlEt3 or KF~2A1Me3. As a re-~s sult of changing the alkali metal cation to potassium, these complexes have improved electrical conductivity and a substantially improved throwing power comparable to other depositions of metal in aqueous electrolytes.
zo However, these compounds involve a severe drawback in that their melting points are about 127-129~C for KF~2AlEt3 and 1S1-152~C for KF~2A1Me3, respectively. Also, the solubility of these complexes in aromatic hydrocarbons is very low. Thus, a 4 M toluene solution of KF~2AlEt3 un-zs dergoes crystallization even at 60-6S~C. As a consequence, partial crystallization of: the active aluminum complex compound occurs during storage of such solutions, rende-ring them unserviceable even after a short period of time.
Also, when using the electrolyte, blocking in pipelines, 3o pumps and filters tends to occur as a result of such cry-stallization, so that these solutions cannot be put to reasonable use in an industrial-technical application, e.g. in a production coating plant. Similarly, the measure of diluting the electrolyte solutions and increasing the 5~ percentage of solvent is L.rdesirable because the ~.racti-cable current densities are dramatically decreasa~i in this 970B125. DOC
However, other alkyl aluminum complexes have also been used. Amongst these are, e.g., electrolytes including aluminum complexes such as lKF~2AlEt3 or KF~2A1Me3. As a re-~s sult of changing the alkali metal cation to potassium, these complexes have improved electrical conductivity and a substantially improved throwing power comparable to other depositions of metal in aqueous electrolytes.
zo However, these compounds involve a severe drawback in that their melting points are about 127-129~C for KF~2AlEt3 and 1S1-152~C for KF~2A1Me3, respectively. Also, the solubility of these complexes in aromatic hydrocarbons is very low. Thus, a 4 M toluene solution of KF~2AlEt3 un-zs dergoes crystallization even at 60-6S~C. As a consequence, partial crystallization of: the active aluminum complex compound occurs during storage of such solutions, rende-ring them unserviceable even after a short period of time.
Also, when using the electrolyte, blocking in pipelines, 3o pumps and filters tends to occur as a result of such cry-stallization, so that these solutions cannot be put to reasonable use in an industrial-technical application, e.g. in a production coating plant. Similarly, the measure of diluting the electrolyte solutions and increasing the 5~ percentage of solvent is L.rdesirable because the ~.racti-cable current densities are dramatically decreasa~i in this 970B125. DOC
way, thereby substantially increasing the duration of de-ccs_ .ion.
To scive this problem, the prior art or EP-A 0 402 s 761 and US 4,417,954 suggest=s using complexes of other al-kyl aluminum compounds such as triisobutyl aluminum or trimethyl aluminum in addition to the above-mentioned po-tassium-containing triethyl aluminum complexes. These mi-xed aluminum complexes have lower melting points compared to triethyl aluminum complexes and higher solubility in aromatic hydrocarbons.
The EP-0 402 760 A1 describes electrolytes for the deposition of aluminum which, in addition to compounds of ~s formula MF~2A1R3, contain non-complexed A1R3 and wherein an aromatic hydrocarbon anal a glycol ether are used as solvents.
As yet, the prior art has attempted to overcome Zo these problems of poor throwing power and poor electric conductivity on the one hand, and the problems related to the solubility of the alkyl aluminum complexes on the other hand. by using mixed alkyl aluminum complexes. Thus, complexes having good electric conductivity and throwing zs power, but poor solubility, have been mixed with complexes having good solubility and poor electric conductivity. On an average, a composition had been achieved which was ac-ceptable for industrial processes in terms of its electric conductivity and solubility, as well as its throwing po-3o wer. Even today, deposition of aluminum on an industrial-technical scale is performed using these mixtures. Howe-ver, these electrolyte solutions still involve consider-able drawbacks.
~Ahile compounds having the composition KF
~A1(i-3u)3 have a lower melting point and thereFore are usacui as an additive to improve solubility, larger con-970B12-6.DOC
To scive this problem, the prior art or EP-A 0 402 s 761 and US 4,417,954 suggest=s using complexes of other al-kyl aluminum compounds such as triisobutyl aluminum or trimethyl aluminum in addition to the above-mentioned po-tassium-containing triethyl aluminum complexes. These mi-xed aluminum complexes have lower melting points compared to triethyl aluminum complexes and higher solubility in aromatic hydrocarbons.
The EP-0 402 760 A1 describes electrolytes for the deposition of aluminum which, in addition to compounds of ~s formula MF~2A1R3, contain non-complexed A1R3 and wherein an aromatic hydrocarbon anal a glycol ether are used as solvents.
As yet, the prior art has attempted to overcome Zo these problems of poor throwing power and poor electric conductivity on the one hand, and the problems related to the solubility of the alkyl aluminum complexes on the other hand. by using mixed alkyl aluminum complexes. Thus, complexes having good electric conductivity and throwing zs power, but poor solubility, have been mixed with complexes having good solubility and poor electric conductivity. On an average, a composition had been achieved which was ac-ceptable for industrial processes in terms of its electric conductivity and solubility, as well as its throwing po-3o wer. Even today, deposition of aluminum on an industrial-technical scale is performed using these mixtures. Howe-ver, these electrolyte solutions still involve consider-able drawbacks.
~Ahile compounds having the composition KF
~A1(i-3u)3 have a lower melting point and thereFore are usacui as an additive to improve solubility, larger con-970B12-6.DOC
centrations of this compound in the electrolyte rapidly gi-m rise tc gray depositions. Moreover, the curr:.~_t :en sity resistance of these complexes is low and may rapi:ll result in co-deposition of potassium which is most undesi s rable in aluminum deposition.
Also, the thermal ;stability of these triisobutyl complexes is inferior comp<~red to triethyl aluminum com-plexes.
io The composition of an electroplating bath in ope-ration is subject to continuous changes, and the mixing ratio and concentration of the individual aluminum comple-xes must be maintained con:ctant. For this reason, another disadvantage of these multi.-component systems is the com-as placated control and maini~enance of the composition at constant, as well as the more extensive analytics.
Furthermore, some aluminum complexes such as trimethyl aluminum are so costly that avoiding the use of such a complex compound is desirable merely for economic reasons.
zo It is therefore the technical object of the inven tion to bring about an improvement of the prior art elec trolyte solutions, which would allow a more economic use of the electrolytes and would not necessarily require a zs multi-component system.
Said technical object is accomplished by using an electrolyte in the electrodeposition of aluminum which contains an organometallic: aluminum complex of formula 30 (I) MF~2A1R3 ( I ) , wherein M = Vila, K, Rb, Cs, and R = a Ci-C4 alkyl g=oup, in a solvent mixture of an aromatic or aliphatic hydrocar-bon and a Lewis base.
970A12-S.OOC
'when using prior art electrolyte solutions, aro-mavi: hjdrocarbons such as toluene or x~llene are used al-most exclusively as solvents. Surprisingly, it has now be-er~ found that partial substitution of these aromatic hy-s drocarbons by organic Lewis bases results in a substantial improvement regarding the solubility and other properties of the alkyl aluminum complexes, so that the use of multi-component systems is no longer necessary.
This was a11 the more surprising because when using Lewis bases, a person. skilled in the art should have expected that the aluminum complex, as a result of the high affinity of Lewis basE:s to the A1 atom, would be de-stroyed either completely or partially with elimination of ~s alkali metal halide and addition of the corresponding Le-wis base to the aluminum atom. As one might expect, this should have resulted in such a decrease in conductivity of the aluminum complex that it could no longer be used in an electrolysis.
Amazingly, however,, no such effect was observed when using Lewis bases. Rather, the conductivity of the electrolyte solution remained almost unchanged although, as is known, Lewis bases have a higher affinity to alkyl zs aluminum compounds compared to some alkali metal halides.
In a preferred embodiment, the ratio of employed hydrocarbon solvent to Lewis bases is from 4:1 to 1:2. It is also preferred that M in formula (I) be potassium, ru-3o bidium or cesium. Triethyl aluminum is preferably used as A183 aluminum compound. As Lewis base, it is preferred to use an aliphatic, cycloaliphatic or aromatic ether compo-und or an amine. It is particularly preferred to use an ether of formula R1-0-R2 wherein Rl and R~ are C1-C4 al-s~ kyl. nor examplz, these ethers in~.lude compounds such as methy'_ ethers, ethyl er_he;=s, n-propyl ethers, isopropyl ' 970A12-s.DOC
w ethers, tert-butyl ethers, n-butyl ethers, and isobutyl orhors.
~dhen using the electrolyte solution according to s the invention, the previous multi-component systems can be avoided. It is particularly preferred to use KF~2AlEt3 be-cause this compound genera:Lly is one of the most readily available and inexpensive alkyl aluminum complexes. Pre-viously occurring problems related to the solubility of such complexes can be overcome in a simple fashion by ad-ding a Lewis base to the toluene-containing solution, and in a particularly preferred fashion, diisopropyl ether or an n-propyl ether.
is A 4 M solution of KF~2AlEt3 in toluene normally crystallizes even at room temperature. This is not obser-ved with the electrolyte of the invention in a solvent mixture with Lewis bases. The electric conductivity of the electrolytes according to t:he invention is somewhat lower zo compared to electrolytes in pure toluene, and the decrease in electric conductivity is far less than expected by a person skilled in the art f:or the case of partial or com-plete degradation of the complex. Furthermore, the slight-ly lower conductivity is compensated by higher solubility zs and higher resistance of such an electrolyte solution.
When using the electrolyte solution of the inven-tion, it has also been found that the coating on parts of complicated shape spreads further into crevices and bo-3o rings than is the case with electrolytes with no Lewis ba-ses added. Also, the tendency to dendritic growth or bur-nings is prevented by the inhibiting effect of the added Lewis base. The layers obtained are matte to semi-glossing and low in pores and are produced at current densities of up to ~ A/dm~ . The electro~.ytes may be operated bot~~. with DC and AC.
; 970A12-S.DOC
'' rJsing the electrolyte solution of the invention, i' ~s ocssib_e for the fi:~st time to replace the multi-ccmpcr:ent sls=enis used so f:ar which are expensi-Te and re-quire a high input for maintenance, and at the same time, s obtain improved aluminum coatings.
During the use of an electrolyte solution in elec-troplating, the composition of said solution will be sub-ject to continuous changes. For this reason, in multi-com-ponent systems used so far, the individual components of alkyl aluminum complexes had to be monitored continuously during the electrodeposition of aluminum, and replenished, if necessary. In doing so, care must be taken that the ra-tio of the individual alkyl aluminum compounds employed is ~s held as constant as possible, so as not to alter the properties of the bath in an undesirable fashion.
Such considerable and cost-intensive input can be avoided completely by using the electrolyte solution ac-Zo cording to the invention where only one single alkyl alu-minum compound must be employed, the content of which may easily be monitored. If required, only one single substan-ce must be supplied to the bath without the necessity of paying attention to the ratio between the individual alkyl is aluminum components. The electrolyte of the invention also allows deposition at high current intensities, thereby en-abling more rapid deposition of aluminum and thus, enhan-cing the economic efficiency of the aluminum electroplat-ing process.
The electrolyte solution of the invention is pro-duced in a conventional f<ishion by initially adding the metal fluoride to the solvent mixture of hydrocarbon and a Lewis base. Then, the amount of alkyl aluminum compound calculatad for complex formation is added slowly in small oortior.s. EolLowing addition, this is heated and stirred until a1L the components are completely dissolved. The so-970B12-6.00C
"' lution is then cooled down to room temperature and may be stored 'or any period of time without crystallization of the solution occurring.
s The electrolyte solution of the invention is pref erably used in manufacturing decorative and corrosion-re sistant aluminum coatings. Using the electrolyte solution according to the invention, aluminum layers of high purity and quality may be coated in a simple and highly economic to fashion.
The following Examples are intended to illustrate the invention in more detai:L.
Examples Example 1 Zo Preparation of the electrolyte solution In a heatable stirred vessel, an electrolyte ha-ving the composition KF~2A1:Et3 dissolved in 4 mol of sol-vent mixture per mol of complex was prepared under argon.
Zs The molar ratio of the so:Lvents toluene and diisopropyl ether was 3:1.
To this end, the calculated amount of solvent mix-ture was initially placed into the argon-flooded stirred 3o vessel. Thereafter, potassium fluoride which had been dried at 120~C was added with intense stirring. Subse-quently, the calculated amount of triethyl aluminum was slowly added in small portions, and the solution underwent heating to about 80~C. The solution was then heated to 100 ~C and stirred For 2 hours. The soluti~:n had a conductivi-ty of 19 mS/cm. Thereafter, the solution was cooled to 18~
C without stirring. The solution was completely fluid the-970A125. DOC
_<~_ reafter. Following pouring into a storage vessel, the so '_e'_ior. eras stored for 2 weeks without motion at 15-18~r.
~nen a~'_~r a 2 weeks storage, the solution still was com ,, p~ete?I ~luid.
s Example 2 Coating of stepped angle metal sheets using AC
Coating was performed using the electrolyte of Ex-ample 1. In a coating cell of about 6 1 capacity flooded with argon and equipped with a supply lock system, two stepped angle metal sheets having a step width of 20 mm were coated in a rack panel of about 140 x 140 mm at a ~s current density of 1 A/dm2 and 100~C using AC. The anodes were arranged parallel to i:he rack panel, and the deposi-tion period was 60 minutes.
A finely crystalline, smooth, silken-matte alumi-num layer had been produced., with no burnings or dendritic growth on edges and tips. 'the cathode yield is 99.8. The distribution was about 38~.
Example 3 zs Coating of stepped angle metal sheets using DC
The same experiment as in Example 2 was carried out using 1 A/dm2 DC instead of AC. A finely crystalline, 3o smooth, matte aluminum layer had been produced, with no burnings or dendritic growth on edges and tips. Similarly, the cathode yield was virtually 100. The layer-thickness distribution on the metal sheet was identical to that of Example . . ~ 970B12~S.DOC
Example 4 Coating of a slit cathode ~;J metal sheet) s A slit cathode (J metal sheet) 50 mm in width, ha-ving a slit of 2 mm, was coated for 30 min in the electro-lyte of Example 1 using a current density of 1 A/dm2, with the anodes in parallel arrangement to the flat side of the cathode. Subsequent to bending up the metal sheet, it was found that the coating had spread up to 7 mm from the ed-ge, with a fluid run-out of the coating up to about 16 mm from the edge. About 18 nun in the center of the metal sheet remained uncoated.
is Comparative Example 1 Coating of a slit cathode (J metal sheet) according to EP
zo For comparison, an identical metal sheet was pla-ted under the same conditions as in Example 4 in an electrolyte having only to:Luene as solvent with no diiso-propyl ether added (cf., EP 0 402 761 Al) . In this case, the electrolyte spread only by about 4.5 mm from the edge is into the split, the coating coming to an abrupt halt.
About 41 mm in the center of the metal sheet remained un-coated.
Also, the thermal ;stability of these triisobutyl complexes is inferior comp<~red to triethyl aluminum com-plexes.
io The composition of an electroplating bath in ope-ration is subject to continuous changes, and the mixing ratio and concentration of the individual aluminum comple-xes must be maintained con:ctant. For this reason, another disadvantage of these multi.-component systems is the com-as placated control and maini~enance of the composition at constant, as well as the more extensive analytics.
Furthermore, some aluminum complexes such as trimethyl aluminum are so costly that avoiding the use of such a complex compound is desirable merely for economic reasons.
zo It is therefore the technical object of the inven tion to bring about an improvement of the prior art elec trolyte solutions, which would allow a more economic use of the electrolytes and would not necessarily require a zs multi-component system.
Said technical object is accomplished by using an electrolyte in the electrodeposition of aluminum which contains an organometallic: aluminum complex of formula 30 (I) MF~2A1R3 ( I ) , wherein M = Vila, K, Rb, Cs, and R = a Ci-C4 alkyl g=oup, in a solvent mixture of an aromatic or aliphatic hydrocar-bon and a Lewis base.
970A12-S.OOC
'when using prior art electrolyte solutions, aro-mavi: hjdrocarbons such as toluene or x~llene are used al-most exclusively as solvents. Surprisingly, it has now be-er~ found that partial substitution of these aromatic hy-s drocarbons by organic Lewis bases results in a substantial improvement regarding the solubility and other properties of the alkyl aluminum complexes, so that the use of multi-component systems is no longer necessary.
This was a11 the more surprising because when using Lewis bases, a person. skilled in the art should have expected that the aluminum complex, as a result of the high affinity of Lewis basE:s to the A1 atom, would be de-stroyed either completely or partially with elimination of ~s alkali metal halide and addition of the corresponding Le-wis base to the aluminum atom. As one might expect, this should have resulted in such a decrease in conductivity of the aluminum complex that it could no longer be used in an electrolysis.
Amazingly, however,, no such effect was observed when using Lewis bases. Rather, the conductivity of the electrolyte solution remained almost unchanged although, as is known, Lewis bases have a higher affinity to alkyl zs aluminum compounds compared to some alkali metal halides.
In a preferred embodiment, the ratio of employed hydrocarbon solvent to Lewis bases is from 4:1 to 1:2. It is also preferred that M in formula (I) be potassium, ru-3o bidium or cesium. Triethyl aluminum is preferably used as A183 aluminum compound. As Lewis base, it is preferred to use an aliphatic, cycloaliphatic or aromatic ether compo-und or an amine. It is particularly preferred to use an ether of formula R1-0-R2 wherein Rl and R~ are C1-C4 al-s~ kyl. nor examplz, these ethers in~.lude compounds such as methy'_ ethers, ethyl er_he;=s, n-propyl ethers, isopropyl ' 970A12-s.DOC
w ethers, tert-butyl ethers, n-butyl ethers, and isobutyl orhors.
~dhen using the electrolyte solution according to s the invention, the previous multi-component systems can be avoided. It is particularly preferred to use KF~2AlEt3 be-cause this compound genera:Lly is one of the most readily available and inexpensive alkyl aluminum complexes. Pre-viously occurring problems related to the solubility of such complexes can be overcome in a simple fashion by ad-ding a Lewis base to the toluene-containing solution, and in a particularly preferred fashion, diisopropyl ether or an n-propyl ether.
is A 4 M solution of KF~2AlEt3 in toluene normally crystallizes even at room temperature. This is not obser-ved with the electrolyte of the invention in a solvent mixture with Lewis bases. The electric conductivity of the electrolytes according to t:he invention is somewhat lower zo compared to electrolytes in pure toluene, and the decrease in electric conductivity is far less than expected by a person skilled in the art f:or the case of partial or com-plete degradation of the complex. Furthermore, the slight-ly lower conductivity is compensated by higher solubility zs and higher resistance of such an electrolyte solution.
When using the electrolyte solution of the inven-tion, it has also been found that the coating on parts of complicated shape spreads further into crevices and bo-3o rings than is the case with electrolytes with no Lewis ba-ses added. Also, the tendency to dendritic growth or bur-nings is prevented by the inhibiting effect of the added Lewis base. The layers obtained are matte to semi-glossing and low in pores and are produced at current densities of up to ~ A/dm~ . The electro~.ytes may be operated bot~~. with DC and AC.
; 970A12-S.DOC
'' rJsing the electrolyte solution of the invention, i' ~s ocssib_e for the fi:~st time to replace the multi-ccmpcr:ent sls=enis used so f:ar which are expensi-Te and re-quire a high input for maintenance, and at the same time, s obtain improved aluminum coatings.
During the use of an electrolyte solution in elec-troplating, the composition of said solution will be sub-ject to continuous changes. For this reason, in multi-com-ponent systems used so far, the individual components of alkyl aluminum complexes had to be monitored continuously during the electrodeposition of aluminum, and replenished, if necessary. In doing so, care must be taken that the ra-tio of the individual alkyl aluminum compounds employed is ~s held as constant as possible, so as not to alter the properties of the bath in an undesirable fashion.
Such considerable and cost-intensive input can be avoided completely by using the electrolyte solution ac-Zo cording to the invention where only one single alkyl alu-minum compound must be employed, the content of which may easily be monitored. If required, only one single substan-ce must be supplied to the bath without the necessity of paying attention to the ratio between the individual alkyl is aluminum components. The electrolyte of the invention also allows deposition at high current intensities, thereby en-abling more rapid deposition of aluminum and thus, enhan-cing the economic efficiency of the aluminum electroplat-ing process.
The electrolyte solution of the invention is pro-duced in a conventional f<ishion by initially adding the metal fluoride to the solvent mixture of hydrocarbon and a Lewis base. Then, the amount of alkyl aluminum compound calculatad for complex formation is added slowly in small oortior.s. EolLowing addition, this is heated and stirred until a1L the components are completely dissolved. The so-970B12-6.00C
"' lution is then cooled down to room temperature and may be stored 'or any period of time without crystallization of the solution occurring.
s The electrolyte solution of the invention is pref erably used in manufacturing decorative and corrosion-re sistant aluminum coatings. Using the electrolyte solution according to the invention, aluminum layers of high purity and quality may be coated in a simple and highly economic to fashion.
The following Examples are intended to illustrate the invention in more detai:L.
Examples Example 1 Zo Preparation of the electrolyte solution In a heatable stirred vessel, an electrolyte ha-ving the composition KF~2A1:Et3 dissolved in 4 mol of sol-vent mixture per mol of complex was prepared under argon.
Zs The molar ratio of the so:Lvents toluene and diisopropyl ether was 3:1.
To this end, the calculated amount of solvent mix-ture was initially placed into the argon-flooded stirred 3o vessel. Thereafter, potassium fluoride which had been dried at 120~C was added with intense stirring. Subse-quently, the calculated amount of triethyl aluminum was slowly added in small portions, and the solution underwent heating to about 80~C. The solution was then heated to 100 ~C and stirred For 2 hours. The soluti~:n had a conductivi-ty of 19 mS/cm. Thereafter, the solution was cooled to 18~
C without stirring. The solution was completely fluid the-970A125. DOC
_<~_ reafter. Following pouring into a storage vessel, the so '_e'_ior. eras stored for 2 weeks without motion at 15-18~r.
~nen a~'_~r a 2 weeks storage, the solution still was com ,, p~ete?I ~luid.
s Example 2 Coating of stepped angle metal sheets using AC
Coating was performed using the electrolyte of Ex-ample 1. In a coating cell of about 6 1 capacity flooded with argon and equipped with a supply lock system, two stepped angle metal sheets having a step width of 20 mm were coated in a rack panel of about 140 x 140 mm at a ~s current density of 1 A/dm2 and 100~C using AC. The anodes were arranged parallel to i:he rack panel, and the deposi-tion period was 60 minutes.
A finely crystalline, smooth, silken-matte alumi-num layer had been produced., with no burnings or dendritic growth on edges and tips. 'the cathode yield is 99.8. The distribution was about 38~.
Example 3 zs Coating of stepped angle metal sheets using DC
The same experiment as in Example 2 was carried out using 1 A/dm2 DC instead of AC. A finely crystalline, 3o smooth, matte aluminum layer had been produced, with no burnings or dendritic growth on edges and tips. Similarly, the cathode yield was virtually 100. The layer-thickness distribution on the metal sheet was identical to that of Example . . ~ 970B12~S.DOC
Example 4 Coating of a slit cathode ~;J metal sheet) s A slit cathode (J metal sheet) 50 mm in width, ha-ving a slit of 2 mm, was coated for 30 min in the electro-lyte of Example 1 using a current density of 1 A/dm2, with the anodes in parallel arrangement to the flat side of the cathode. Subsequent to bending up the metal sheet, it was found that the coating had spread up to 7 mm from the ed-ge, with a fluid run-out of the coating up to about 16 mm from the edge. About 18 nun in the center of the metal sheet remained uncoated.
is Comparative Example 1 Coating of a slit cathode (J metal sheet) according to EP
zo For comparison, an identical metal sheet was pla-ted under the same conditions as in Example 4 in an electrolyte having only to:Luene as solvent with no diiso-propyl ether added (cf., EP 0 402 761 Al) . In this case, the electrolyte spread only by about 4.5 mm from the edge is into the split, the coating coming to an abrupt halt.
About 41 mm in the center of the metal sheet remained un-coated.
Claims (7)
1. An electrolyte for the electrodeposition of aluminum, containing an organometallic aluminum complex of formula (I):
MF~2ALR3 (I), wherein M = Na, K, Rb, Cs, and R = a C1-C4 alkyl group, in a solvent mixture of an aromatic or aliphatic hydrocarbon, and a Lewis base.
MF~2ALR3 (I), wherein M = Na, K, Rb, Cs, and R = a C1-C4 alkyl group, in a solvent mixture of an aromatic or aliphatic hydrocarbon, and a Lewis base.
2. The electrolyte of claim 1, characterized in that the ratio of hydrocarbon to Lewis base is from 4:1 to 1:2.
3. The electrolyte according to claim 1 or 2, characterized in that M :in formula (I) is K, Rb, Cs.
4. The electrolyte according to claims 1 through 3, characterized in that Al83 in formula (I) is AlEt3.
5. The electrolyte according to claims 1 through 4, characterized in that. an aliphatic, cycloaliphatic or aromatic ether or an amine is included as Lewis base.
6. The electrolyte according to claims 1 through 5, characterized in that an ether of formula R1-O-R2 is included as Lewis base, wherein R1 and R2 are C1-C4 alkyl.
7. Use of the electrolyte according to claims 1 through 6 in manufacturing decorative corrosion-resistant aluminum coatings.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19649000.6 | 1996-11-27 | ||
| DE19649000A DE19649000C1 (en) | 1996-11-27 | 1996-11-27 | Electrolyte for the electrodeposition of aluminum and its use |
| PCT/EP1997/006218 WO1998023795A2 (en) | 1996-11-27 | 1997-11-08 | Electrolyte for aluminium electroplating |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2272254A1 true CA2272254A1 (en) | 1998-06-04 |
Family
ID=7812844
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002272254A Abandoned CA2272254A1 (en) | 1996-11-27 | 1997-11-08 | Electrolyte for aluminium electroplating |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0948670B1 (en) |
| JP (1) | JP2001505253A (en) |
| AT (1) | ATE225871T1 (en) |
| AU (1) | AU5320098A (en) |
| CA (1) | CA2272254A1 (en) |
| DE (2) | DE19649000C1 (en) |
| ES (1) | ES2186010T3 (en) |
| WO (1) | WO1998023795A2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002088434A1 (en) * | 2001-04-30 | 2002-11-07 | Alumiplate Incorporated | Aluminium electroplating formulations |
| US7250102B2 (en) | 2002-04-30 | 2007-07-31 | Alumiplate Incorporated | Aluminium electroplating formulations |
| EP1647613A1 (en) * | 2004-10-15 | 2006-04-19 | Aluminal Oberflächentechnik GmbH & Co. KG | Electrolyte for galvanic deposition of aluminium |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE758730A (en) * | 1969-12-27 | 1971-04-16 | Nisshin Steel Co Ltd | ALUMINUM COATING PROCESS |
| DE2453830C2 (en) * | 1974-11-13 | 1986-07-31 | Siemens AG, 1000 Berlin und 8000 München | Bath and process for the galvanic deposition of shiny aluminum coatings |
| DE3202265A1 (en) * | 1982-01-25 | 1983-07-28 | Siemens AG, 1000 Berlin und 8000 München | ELECTROLYTE FOR GALVANIC DEPOSITION OF ALUMINUM |
| DE3919069A1 (en) * | 1989-06-10 | 1990-12-13 | Studiengesellschaft Kohle Mbh | ALUMINUM ORGANIC ELECTROLYTE AND METHOD FOR ELECTROLYTICALLY DEPOSITING ALUMINUM |
| DE3919068A1 (en) * | 1989-06-10 | 1990-12-13 | Studiengesellschaft Kohle Mbh | ALUMINUM ORGANIC ELECTROLYTE FOR THE ELECTROLYTIC DEPOSITION OF HIGH-PURITY ALUMINUM |
-
1996
- 1996-11-27 DE DE19649000A patent/DE19649000C1/en not_active Expired - Fee Related
-
1997
- 1997-11-08 JP JP52419998A patent/JP2001505253A/en active Pending
- 1997-11-08 CA CA002272254A patent/CA2272254A1/en not_active Abandoned
- 1997-11-08 DE DE59708456T patent/DE59708456D1/en not_active Expired - Lifetime
- 1997-11-08 EP EP97950148A patent/EP0948670B1/en not_active Expired - Lifetime
- 1997-11-08 ES ES97950148T patent/ES2186010T3/en not_active Expired - Lifetime
- 1997-11-08 AU AU53200/98A patent/AU5320098A/en not_active Abandoned
- 1997-11-08 AT AT97950148T patent/ATE225871T1/en not_active IP Right Cessation
- 1997-11-08 WO PCT/EP1997/006218 patent/WO1998023795A2/en active IP Right Grant
Also Published As
| Publication number | Publication date |
|---|---|
| JP2001505253A (en) | 2001-04-17 |
| DE59708456D1 (en) | 2002-11-14 |
| WO1998023795A3 (en) | 1998-07-09 |
| AU5320098A (en) | 1998-06-22 |
| WO1998023795A2 (en) | 1998-06-04 |
| DE19649000C1 (en) | 1998-08-13 |
| ATE225871T1 (en) | 2002-10-15 |
| ES2186010T3 (en) | 2003-05-01 |
| EP0948670A2 (en) | 1999-10-13 |
| EP0948670B1 (en) | 2002-10-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4904355A (en) | Plating bath for electrodeposition of aluminum and plating process making use of the bath | |
| EP0398358B1 (en) | Aluminum electroplating method | |
| JP4986122B2 (en) | Electrolytic aluminum plating solution and aluminum plating film | |
| US4747916A (en) | Plating bath for electrodeposition of aluminum and process for the same | |
| CA2352800A1 (en) | Aluminium organic electrolytes and method for electrolytic coating with aluminium or aluminium-magnesium-alloys | |
| JP2918634B2 (en) | Organic aluminum electrolyte and method for electrodeposition of aluminum | |
| US4906342A (en) | Plating bath for electrodeposition of aluminum and plating process making use of the bath | |
| CA2272254A1 (en) | Electrolyte for aluminium electroplating | |
| US3595760A (en) | Electrodeposition of aluminium | |
| JP2918635B2 (en) | Organic aluminum electrolyte for high purity aluminum electrodeposition. | |
| US6207036B1 (en) | Electrolytic high-speed deposition of aluminum on continuous products | |
| US3672965A (en) | Electroplating of aluminum | |
| MXPA99004855A (en) | Electrolyte for aluminium electroplating | |
| JPH03134193A (en) | Low-melting point composition and electric aluminum plating method | |
| US3278400A (en) | Electroforming of beryllium | |
| MXPA99009527A (en) | Electrolytic high-speed deposition of aluminium on continuous products | |
| JP2689274B2 (en) | Electric aluminum plating bath | |
| JPH0361392A (en) | Composition having low melting point and aluminum electroplating method using the same as bath | |
| JPH0421794A (en) | Composition having low melting point and aluminum electroplating method | |
| US4381975A (en) | Aluminium electroplating solution | |
| JPH04231492A (en) | Low melting composition and electrogalvanizing method | |
| JPH04231493A (en) | Low melting composition and electrochrome plating method | |
| JPH0196390A (en) | Production of high purity chromium by electrolysis and electrolytic bath therefor | |
| CA1311710C (en) | Plating bath for electrodeposition of aluminum and process for the same | |
| JP2020066782A (en) | Method of producing aluminum using hydrate |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |