CA1142477A - Process for the electrolytic colouring of anodized aluminium - Google Patents
Process for the electrolytic colouring of anodized aluminiumInfo
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- CA1142477A CA1142477A CA000356557A CA356557A CA1142477A CA 1142477 A CA1142477 A CA 1142477A CA 000356557 A CA000356557 A CA 000356557A CA 356557 A CA356557 A CA 356557A CA 1142477 A CA1142477 A CA 1142477A
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Abstract
ABSTRACT OF THE DISCLOSURE
The invention provides a process for the electrolytic colouring of anodized aluminium, characterized in that in the first step thereof an aluminium oxide layer is produced on the metal using a sulphuric acid bath which has a concentration of from 150 to 200 g/l, a voltage between electrodes of from 12 to 20 volts, and a current density of from 1 to a A/dm2, the duration of this treatment being of from 15 to 60 minutes, while the second step of the process consisting introducing the metal into a colouring bath in which two different electrolytic steps are established, in the first of which the metal is subjected to a continuous pulsating voltage, while in the second a negative continuous pulsating voltage is programmed on the wave form of the first step.
The invention provides a process for the electrolytic colouring of anodized aluminium, characterized in that in the first step thereof an aluminium oxide layer is produced on the metal using a sulphuric acid bath which has a concentration of from 150 to 200 g/l, a voltage between electrodes of from 12 to 20 volts, and a current density of from 1 to a A/dm2, the duration of this treatment being of from 15 to 60 minutes, while the second step of the process consisting introducing the metal into a colouring bath in which two different electrolytic steps are established, in the first of which the metal is subjected to a continuous pulsating voltage, while in the second a negative continuous pulsating voltage is programmed on the wave form of the first step.
Description
~Z~7 The pxesent invention relates to a process for the electrolytic colouring of anodized aluminium.
Although the baths and procedures used in the pro-cesses for the el~ctrolytic colouring of anodized aluminium with inorganic pigments have increased the number of patents existing on thls subject, it is a fact that the colours pro-duced with the mentioned technique are, at an industrial scale, rather poor.
The search for new baths and processes, with the idea of obtaining new colours, has been the general trend in this field and thus in 1968 French patent 1,605,100 developed a novel method for colouring, whereby yellow and brick-red colours were obtained by the partial anodic dissolution of the particles deposited in the bottom of the blister in a sodium thiosulphate solution.
Subsequently German patents 2,106,388 and 2,106,339 cited a new process for obtaining bluish colours which mainly consisted in electrodepositing metals such as Cu, Co and Ni on a chromic acid formed anodic layer and simultaneously stamping the samples under special conditions. This process has the disadvantage that the colouring can only take place on chromic acid anodized samples to produce the new colours and besides stamping should take place in specific solutions.
From 1974 onwards there appeared various patents, inter alia, Spanish patent 437,604 and French patent 2,236,029, whereby colours other than those normally obtained in the electrolytic colouring baths were achieved by using high con-centrations of sulphuric acid.
These processes have the typical disadvantage of working with high proton concentrations, i.e. the possibility of producing spalling at not very high voltages. There is another important problem which should be emphasized, i.e. the com-petition between the discharge of the ions, less noble thanhydrogen, and the proton itself. Due to this disadvantage dark tones cannot be achieved in the majority of the baths. However, the high proton concentration can cause losses in the intensity of the colour and in the washing and stamping processes.
Subsequently, French Patent 2,318,245, using a double anodizing process, obtained a wlde range of colours and tones ~y the optical interference between the light reflected by the colouring pigment and that reflected by the surface of the aluminium.
The process for obtaining this type of colouring by optical interference has the disadvantage that, in order to ob-tain the new colours, the elements should be subjected to a chemical or an electrolytic treatment between the anodizing and the colouring process, so that the complete blister, or at least the bottom thereof, is widened.
Another feature of this patent resides in using in the anodizing process voltages greater than 35 volts. This produces serious disadvantages in the baths normally used in these pro-cesses.
Subsequently, French Patent 2,380,257, produced dif-ferent coloured electro-deposits on the aluminium, which electro-deposits had the disadvantage of not being adherent nor resis-tant to corrosion. Therefore, it was necessary to apply a layer of lacquer or varnish to the samples treated with said process.
. ,,~
~ 3 _ ~4~
.
The process of the present invention has the fo' lowing advantages when compared with the known techniqu2 set forth in the aforementioned patents:
1. It permits pH values greater than 0.8 ~o be operated with.
Although the baths and procedures used in the pro-cesses for the el~ctrolytic colouring of anodized aluminium with inorganic pigments have increased the number of patents existing on thls subject, it is a fact that the colours pro-duced with the mentioned technique are, at an industrial scale, rather poor.
The search for new baths and processes, with the idea of obtaining new colours, has been the general trend in this field and thus in 1968 French patent 1,605,100 developed a novel method for colouring, whereby yellow and brick-red colours were obtained by the partial anodic dissolution of the particles deposited in the bottom of the blister in a sodium thiosulphate solution.
Subsequently German patents 2,106,388 and 2,106,339 cited a new process for obtaining bluish colours which mainly consisted in electrodepositing metals such as Cu, Co and Ni on a chromic acid formed anodic layer and simultaneously stamping the samples under special conditions. This process has the disadvantage that the colouring can only take place on chromic acid anodized samples to produce the new colours and besides stamping should take place in specific solutions.
From 1974 onwards there appeared various patents, inter alia, Spanish patent 437,604 and French patent 2,236,029, whereby colours other than those normally obtained in the electrolytic colouring baths were achieved by using high con-centrations of sulphuric acid.
These processes have the typical disadvantage of working with high proton concentrations, i.e. the possibility of producing spalling at not very high voltages. There is another important problem which should be emphasized, i.e. the com-petition between the discharge of the ions, less noble thanhydrogen, and the proton itself. Due to this disadvantage dark tones cannot be achieved in the majority of the baths. However, the high proton concentration can cause losses in the intensity of the colour and in the washing and stamping processes.
Subsequently, French Patent 2,318,245, using a double anodizing process, obtained a wlde range of colours and tones ~y the optical interference between the light reflected by the colouring pigment and that reflected by the surface of the aluminium.
The process for obtaining this type of colouring by optical interference has the disadvantage that, in order to ob-tain the new colours, the elements should be subjected to a chemical or an electrolytic treatment between the anodizing and the colouring process, so that the complete blister, or at least the bottom thereof, is widened.
Another feature of this patent resides in using in the anodizing process voltages greater than 35 volts. This produces serious disadvantages in the baths normally used in these pro-cesses.
Subsequently, French Patent 2,380,257, produced dif-ferent coloured electro-deposits on the aluminium, which electro-deposits had the disadvantage of not being adherent nor resis-tant to corrosion. Therefore, it was necessary to apply a layer of lacquer or varnish to the samples treated with said process.
. ,,~
~ 3 _ ~4~
.
The process of the present invention has the fo' lowing advantages when compared with the known techniqu2 set forth in the aforementioned patents:
1. It permits pH values greater than 0.8 ~o be operated with.
2. It does not require a re-anodizing bath, i.e.
this process fo~ows the known two-phase colouring process.
It produces finishes having a wide range of colours and tones resistant to light and to corrosion.
The process for the electrolytic colouring of ano-dized aluminium of this invention~ ~ommences by producing an aluminium oxide layer on the metal using the conventional method in a sulphuric acid bath, but with a concentration of ~rom lSO to 200 g/l, a voltage between ele~trodes of from 12 to 20 volts, and a current density of from 1 to 2 A/dm2.
The duration of this treatment ~ be of from 15 minutes to 1 hour.
Once the anodic layer of the pleces is obtainad~
these are introduced in the colouring bath.
In the mentioned colouring bath the piece is sub-~ected to two different elec~rolytic steps. Thus, the irst step consists in subjectLng the anodized aluminium piece to a continuous puIsating voltage, fixed or programmed, the duration o~ which electrolytic treatment Yarying ~rom 3 to 10 minutes and the average voltages used also varyi~g from 7 ts 35 volts. The type of waYe used ~n this first step of the colouring treatment can be wavy or of any o~her type.
The second step of the treatment consists of various possibilitiesO ~irstly~ a nesative ~:ontinuQus pul sating ~ol tage can be programmed on the wava ~orm of the , ~z~
first step for a period of time of from 2 to 30 minutes, depend-ing on the colour and tone to be obtained. The peak voltages of the negative semi-wave, to obtain different colours and tones, depend on the required treatment times and on the peak voltage of the positive semi-wave, but they can .range of from 7 to 25 volts.
The aforegoing description will more clearly be under-stood when taken in conjunction with the set of accompanying graphs, wherein the following is represented:
Figure 1 illustrates the type of voltage to which the aluminium piece is subjected in the first of the two electroly-tic steps of which the second phase of the process is comprised;
Figure 2 illustrates the voltage corresponding to the second electrolytic step to which the piece is subjected;
Figure 3 illustrates a variant of the voltage that can be applied to the aluminium piece in the mentioned second elec-trolytic step;
Figure 4 illustrates another variant of this same vol-tage applied to the second step;
Figure 5 illustrates the anodic and cathodic peak voltages used in an example of practical application;
Figure 6 illustrates the cathodic current density cor-responding to the same example of practical application;
Figure 7 illustrates the anodic current density in the mentioned example; and Figure 8, which is on the same sheet as Figure 4, is another variant of the voltage applied in the second step.
Thus, as can be seen, in the first electrolytic step corresponding to the second phase of the process the aluminium piece is subjected to a fixed or programmed con--- ; ;, .~ .
. - 5 -tinuous ~ulsating voltage, as lll~strated in figure l~ ~Jhile in the second step of the treatment a negative continous pulsating voltage can be programmed~ as illustrated in f~gure 2, on the wave form of the irst step7 this second step urthermore permitting the possibilities re1ected in figures 3 and ~ according to which the aluminium piece, a-h~4v ter the first step has~ ompleted, is subjected to a treat-ment under potentiostatic conditions with polarized or non-polarized currents.
The baths used in ~hese electric treatments are characteris~d in ~hat they conta~-., a3 the colou~i.ns sub-stances, metal salts of the group o Cu~ Sn~ Ni and Co~ or mixtures of said 5alts. Any type o anion can be used with said catlons9 although sulphates will preferably be used.
The pH of the work should b~ greater than 0~8 and the working temperature can be of from 15 to 25 without noticising remarkable changes in colour.
The concentrations of the colour producing salts can be of ~rom 5 to S0 g/lo The following examples illustrate practical appli-cations of the process for the electrolytic colouring of anodized aluminium~
EXA~PI,E 1 . A test sample? anodized in a mixture of sul-phuric and ~xalic acids, the concentration o the former bei.ng of.l65 9~1 and that of the latter being of 30 g/l, a~ introduced in a bath cQntainlng:
- S04Cu XH20 ~Ø.............. ~0 q/l Tal^tarlc acid 0~ O~-~O 30 yfl Boric acid 9 ~ 0 ~ 0 ~ 30 g/l pH ~ l.S
.. , . , ... , ,, , ., , . ~ ... , .. , .. . . . . ,, .. ., . , . ~ .. .. . . .. . .. . . . . .
` -- 6 _ ~Z~7 .
The pH was adjusted by using 1 N sulphuric acid or MgO where the resulting pH was lower than 1.5.
The anodized test sample ~as subjected in the first step to an alternating voltage as that illustrated in figure 19 i.e. a positive peak vol~age of 25 volts for a period of time of 7 minutes. This period of time ha~ing lapsed, the negative voltage was increased to 12 peak volts, whereby the colouring processes commenced. The following chromatic scale was obtained.
Time (minutes) ColoOur 1 .~..~OO~.OO....O Violet grey 2 ~ ............... O.O ~ronze
this process fo~ows the known two-phase colouring process.
It produces finishes having a wide range of colours and tones resistant to light and to corrosion.
The process for the electrolytic colouring of ano-dized aluminium of this invention~ ~ommences by producing an aluminium oxide layer on the metal using the conventional method in a sulphuric acid bath, but with a concentration of ~rom lSO to 200 g/l, a voltage between ele~trodes of from 12 to 20 volts, and a current density of from 1 to 2 A/dm2.
The duration of this treatment ~ be of from 15 minutes to 1 hour.
Once the anodic layer of the pleces is obtainad~
these are introduced in the colouring bath.
In the mentioned colouring bath the piece is sub-~ected to two different elec~rolytic steps. Thus, the irst step consists in subjectLng the anodized aluminium piece to a continuous puIsating voltage, fixed or programmed, the duration o~ which electrolytic treatment Yarying ~rom 3 to 10 minutes and the average voltages used also varyi~g from 7 ts 35 volts. The type of waYe used ~n this first step of the colouring treatment can be wavy or of any o~her type.
The second step of the treatment consists of various possibilitiesO ~irstly~ a nesative ~:ontinuQus pul sating ~ol tage can be programmed on the wava ~orm of the , ~z~
first step for a period of time of from 2 to 30 minutes, depend-ing on the colour and tone to be obtained. The peak voltages of the negative semi-wave, to obtain different colours and tones, depend on the required treatment times and on the peak voltage of the positive semi-wave, but they can .range of from 7 to 25 volts.
The aforegoing description will more clearly be under-stood when taken in conjunction with the set of accompanying graphs, wherein the following is represented:
Figure 1 illustrates the type of voltage to which the aluminium piece is subjected in the first of the two electroly-tic steps of which the second phase of the process is comprised;
Figure 2 illustrates the voltage corresponding to the second electrolytic step to which the piece is subjected;
Figure 3 illustrates a variant of the voltage that can be applied to the aluminium piece in the mentioned second elec-trolytic step;
Figure 4 illustrates another variant of this same vol-tage applied to the second step;
Figure 5 illustrates the anodic and cathodic peak voltages used in an example of practical application;
Figure 6 illustrates the cathodic current density cor-responding to the same example of practical application;
Figure 7 illustrates the anodic current density in the mentioned example; and Figure 8, which is on the same sheet as Figure 4, is another variant of the voltage applied in the second step.
Thus, as can be seen, in the first electrolytic step corresponding to the second phase of the process the aluminium piece is subjected to a fixed or programmed con--- ; ;, .~ .
. - 5 -tinuous ~ulsating voltage, as lll~strated in figure l~ ~Jhile in the second step of the treatment a negative continous pulsating voltage can be programmed~ as illustrated in f~gure 2, on the wave form of the irst step7 this second step urthermore permitting the possibilities re1ected in figures 3 and ~ according to which the aluminium piece, a-h~4v ter the first step has~ ompleted, is subjected to a treat-ment under potentiostatic conditions with polarized or non-polarized currents.
The baths used in ~hese electric treatments are characteris~d in ~hat they conta~-., a3 the colou~i.ns sub-stances, metal salts of the group o Cu~ Sn~ Ni and Co~ or mixtures of said 5alts. Any type o anion can be used with said catlons9 although sulphates will preferably be used.
The pH of the work should b~ greater than 0~8 and the working temperature can be of from 15 to 25 without noticising remarkable changes in colour.
The concentrations of the colour producing salts can be of ~rom 5 to S0 g/lo The following examples illustrate practical appli-cations of the process for the electrolytic colouring of anodized aluminium~
EXA~PI,E 1 . A test sample? anodized in a mixture of sul-phuric and ~xalic acids, the concentration o the former bei.ng of.l65 9~1 and that of the latter being of 30 g/l, a~ introduced in a bath cQntainlng:
- S04Cu XH20 ~Ø.............. ~0 q/l Tal^tarlc acid 0~ O~-~O 30 yfl Boric acid 9 ~ 0 ~ 0 ~ 30 g/l pH ~ l.S
.. , . , ... , ,, , ., , . ~ ... , .. , .. . . . . ,, .. ., . , . ~ .. .. . . .. . .. . . . . .
` -- 6 _ ~Z~7 .
The pH was adjusted by using 1 N sulphuric acid or MgO where the resulting pH was lower than 1.5.
The anodized test sample ~as subjected in the first step to an alternating voltage as that illustrated in figure 19 i.e. a positive peak vol~age of 25 volts for a period of time of 7 minutes. This period of time ha~ing lapsed, the negative voltage was increased to 12 peak volts, whereby the colouring processes commenced. The following chromatic scale was obtained.
Time (minutes) ColoOur 1 .~..~OO~.OO....O Violet grey 2 ~ ............... O.O ~ronze
3 ~ 0~5~0~ 0~ Blue-grey
4 .~....... OO...... ...Violet
5 D ~ O ~ Brown ` A sample, anodiæed in a so1utisn of sulphuric acid having a concentration of 165 gJl, was introduced in a bath containing:
BO3H3 ~ 400~00~0~ 30 g/l n o-~c---.-o-.~.A~ 0 5~4H 2 ' ~ D <~ O ~ lQ
Tartaric acld ~ .c.~.~.. 15 t~
pH = OO9 The anodized sample was sub~ected~ in the first step9 to a continuous voltage as that illustrated in figure 1. That is~ a positlve peak voltage of 30 volts for a period of 12 minutes. Once this period of time had lapsed~
the negativ2 voltage was increased to 14 volts~ whereby the colouring process commenced ? obtaining the following 7~7 chromatlc scale:
Ti~e (minutes) Colour ~ 0O.OO~ ...O Llght bronze 5 ~ ~ o ~ o r ~ llow 10 .~..Ø~...O Blue-grey 14 ~Q-~ O~ Green 18 0~.O.. ~....... ..Bronze 25 ~.. 0.......... ~ Black eXAMPLE 3 A test sample, anodized follQwing the procedure o4 Ex~mple 17 was ~ntroduced in the ~olourln~ solution of the same example.
The anodized test sample was subjected, ln the first step, to a half-~ave continuous pulsating voltage - having a maximum voltage of 30 ~olts and it was maintain-ed under these conditions for 5 minutesc This period of time having lapsed, the increase of the negative peak Yol ~ o tage was programmed at a speed o 4Vtminute, un-til a maxi-mum voltage o4 12 volts. At the end of ~hese 7 minutes, from the initiation of the programming of the negative voltage, the sample adopted a uni~orm olive-green colour.
. Subsequent research in this same field ~ to thè conclusion that the continuous pulsating voltage used ~n the first step of the second phase of the process, with values of ~rom 7 to 35 vol ts, should be usf~d for a maxi-mum period of ti~e of 30 minutes, maintaining the minimum duration thereo at 3 minutes.
It was likewise concluded tha~ the metal should be sub~ect~d to potentiostatlc conditions with polari7.ed or non-polarized currents during this first st~p of the pr o ~
. s~cond phase o~ the process. In this ~et~en~ the vol~-2~
tage applied during the first step can colncide with that previously applied in the second step as illustrated in figure 2, or a voltage of the type illustrated in figure 8 A programmed or fixed negati.ve continuous pul sating ~oltage can be applied to the previously mentioned wave form, corresponding to this first step of the second phase of the process, also for a period of time of from 3 to 30 minutes7 depending on the colour and tone to be ob-tained in the following stepO
The peak voltages of the negative semi-wave to o~ain d~fr~rerlt colours and tones depend or, th~ r2q~ir treatment times and on the peak voltage of the positive semi-wave, but can range from 2 to 15 volts, provided that this voltage does not colour.
During the second step of this second phase of the process, the piece already prepared is subjected to colouring. The baths used for thesè electric treatments are those already rnentioned and are characterised in that they contain colourin~ substances, such as metal salts of the group Cu, Sn, N1 and Co1 or mixtures of said metals~
, .
.
,
BO3H3 ~ 400~00~0~ 30 g/l n o-~c---.-o-.~.A~ 0 5~4H 2 ' ~ D <~ O ~ lQ
Tartaric acld ~ .c.~.~.. 15 t~
pH = OO9 The anodized sample was sub~ected~ in the first step9 to a continuous voltage as that illustrated in figure 1. That is~ a positlve peak voltage of 30 volts for a period of 12 minutes. Once this period of time had lapsed~
the negativ2 voltage was increased to 14 volts~ whereby the colouring process commenced ? obtaining the following 7~7 chromatlc scale:
Ti~e (minutes) Colour ~ 0O.OO~ ...O Llght bronze 5 ~ ~ o ~ o r ~ llow 10 .~..Ø~...O Blue-grey 14 ~Q-~ O~ Green 18 0~.O.. ~....... ..Bronze 25 ~.. 0.......... ~ Black eXAMPLE 3 A test sample, anodized follQwing the procedure o4 Ex~mple 17 was ~ntroduced in the ~olourln~ solution of the same example.
The anodized test sample was subjected, ln the first step, to a half-~ave continuous pulsating voltage - having a maximum voltage of 30 ~olts and it was maintain-ed under these conditions for 5 minutesc This period of time having lapsed, the increase of the negative peak Yol ~ o tage was programmed at a speed o 4Vtminute, un-til a maxi-mum voltage o4 12 volts. At the end of ~hese 7 minutes, from the initiation of the programming of the negative voltage, the sample adopted a uni~orm olive-green colour.
. Subsequent research in this same field ~ to thè conclusion that the continuous pulsating voltage used ~n the first step of the second phase of the process, with values of ~rom 7 to 35 vol ts, should be usf~d for a maxi-mum period of ti~e of 30 minutes, maintaining the minimum duration thereo at 3 minutes.
It was likewise concluded tha~ the metal should be sub~ect~d to potentiostatlc conditions with polari7.ed or non-polarized currents during this first st~p of the pr o ~
. s~cond phase o~ the process. In this ~et~en~ the vol~-2~
tage applied during the first step can colncide with that previously applied in the second step as illustrated in figure 2, or a voltage of the type illustrated in figure 8 A programmed or fixed negati.ve continuous pul sating ~oltage can be applied to the previously mentioned wave form, corresponding to this first step of the second phase of the process, also for a period of time of from 3 to 30 minutes7 depending on the colour and tone to be ob-tained in the following stepO
The peak voltages of the negative semi-wave to o~ain d~fr~rerlt colours and tones depend or, th~ r2q~ir treatment times and on the peak voltage of the positive semi-wave, but can range from 2 to 15 volts, provided that this voltage does not colour.
During the second step of this second phase of the process, the piece already prepared is subjected to colouring. The baths used for thesè electric treatments are those already rnentioned and are characterised in that they contain colourin~ substances, such as metal salts of the group Cu, Sn, N1 and Co1 or mixtures of said metals~
, .
.
,
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the electrolytic colouring of anodiz-ed aluminium in which in a first step thereof an aluminium oxide layer is produced on the metal using a sulphuric acid bath which has a concentration of from 150 to 200 g/l. a voltage between electrodes of from 12 to 20 volts, and a current density of from 1 to 2 A/dm2, the duration of this treatment being from 15 to 60 minutes, and in a second step of the process the metal is in-troduced into a colouring bath in which two different electro-lytic steps are effected, in the first of which the metal is sub-jected to a continuous pulsating voltage, while in the second a negative continuous pulsating voltage is programmed on the wave form of the first step.
2. A process according to claim 1, in which the aver-age voltage applied in the first step of the second phase is be-tween 7 to 35 volts, the application time of the electrolytic treatment varying from 3 to 10 minutes.
3. A process according to claim 1, in which the con-tinuous voltage is applied in the second step of the second phase for a period of time of from 2 to 30 minutes, depending on the colour and the tone to be obtained, the value of this applied voltage being from 7 to 25 volts, referring to the peak value of the negative semi-wave, said value depending on the colour, the tone and the treatment time.
4. A process according to claims 1 or 2, in which the metal is subjected to potentiostatic conditions with polarized or non-polarized currents in the second step of the second phase.
5. A process according to claims 1, 2 or 3, in which the application time of the treatment, corresponding to the first step of the second phase, is of from 3 to 30 minutes.
6. A process according to claims 1, 2 or 3, in which during the first step of the second phase a programmed or fixed negative continuous pulsating voltage is applied to the continu-ous pulsating voltage for a period of time of from 3 to 30 minutes, and the peak values of said voltage, in turn, range from 2 to 15 volts, depending on the peak voltages of the positive semi-wave and on the colours and tones to be obtained.
7. A process according to claims 1, 2 or 3, in which during the first step of the second phase of the treatment the metal is subjected to potentiostatic conditions by means of polarized currents.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000356557A CA1142477A (en) | 1980-07-18 | 1980-07-18 | Process for the electrolytic colouring of anodized aluminium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000356557A CA1142477A (en) | 1980-07-18 | 1980-07-18 | Process for the electrolytic colouring of anodized aluminium |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142477A true CA1142477A (en) | 1983-03-08 |
Family
ID=4117464
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000356557A Expired CA1142477A (en) | 1980-07-18 | 1980-07-18 | Process for the electrolytic colouring of anodized aluminium |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1142477A (en) |
-
1980
- 1980-07-18 CA CA000356557A patent/CA1142477A/en not_active Expired
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