CA1059059A - Producing a coloured oxide on an article of aluminium or aluminium alloy - Google Patents

Producing a coloured oxide on an article of aluminium or aluminium alloy

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Publication number
CA1059059A
CA1059059A CA172,956A CA172956A CA1059059A CA 1059059 A CA1059059 A CA 1059059A CA 172956 A CA172956 A CA 172956A CA 1059059 A CA1059059 A CA 1059059A
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Prior art keywords
electrode
electrodes
aluminum alloy
aluminum
oxide coating
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Expired
Application number
CA172,956A
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French (fr)
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CA172956S (en
Inventor
Kenji Wada
Yasushi Suzuki
Kazuyoshi Kaneda
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RIKEN LIGHT METAL INDUSTRIES Co
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RIKEN LIGHT METAL INDUSTRIES Co
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Priority to JP5557472A priority Critical patent/JPS548173B2/ja
Priority to JP11286872A priority patent/JPS5248587B2/ja
Application filed by RIKEN LIGHT METAL INDUSTRIES Co filed Critical RIKEN LIGHT METAL INDUSTRIES Co
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Publication of CA1059059A publication Critical patent/CA1059059A/en
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Classifications

    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25DPROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02Anodisation
    • C25D11/04Anodisation of aluminium or alloys based thereon
    • C25D11/18After-treatment, e.g. pore-sealing
    • C25D11/20Electrolytic after-treatment
    • C25D11/22Electrolytic after-treatment for colouring layers
    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25DPROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02Anodisation
    • C25D11/024Anodisation under pulsed or modulated current or potential
    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25DPROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02Anodisation
    • C25D11/04Anodisation of aluminium or alloys based thereon

Abstract

ABSTRACT OF THE DISCLOSURE
A method of producing a colored oxide coating on aluminum or aluminum alloy includes first forming an oxide coating on the aluminum or aluminum alloy by anodic oxidation.
The coated aluminum or aluminum alloy is then arranged to form a first of a pair of electrodes in an electrolytic bath containing metal ions, and first and second voltages are alternately applied across the electrodes to produce first and second direct currents respectively flowing in opposite direc-tions, with the voltage across the electrodes when the first electrode is cathodic being sufficiently large to cause electrolytic deposition of the metal ions on the oxide coating, thereby coloring the coating.

Description

: ` ` 1059059 The present invention relates to a method of producinq a colored oxide coating on aluminum or aluminum alloy (referred to as aluminous material hereafter) and particularly a method for easily producing a colored oxide coating having an excellent reproductivity of color tone.
Heretofore, various processes have been proposed whereïn an aluminous material is subjected to an anodic oxida-tion treatment by passing a direct or alternating current or these currents simultaneously through an electrolytic bath con-sisting of a solution of a mineral acid, an organic acid or asalt of these acids and containing a small amount of a metal salt, to absorb the metal in the metal salt or its compound into an oxide film which forms on the aluminous material to provide a colored oxide film showing an inherent color of the metal salt.
For example, using an alternating current, the following processes have been proposed:
(a) An inorganic coloring process of an aluminous material by means of alternate electrolysis in Japanese Patent 310,401 in the name of T. Asada and published on March S, 1963.
(b) A process for treating a surface of an aluminous material by means of both alternating current and direct current in Japanese Patent Application Publication No. 19,842/71 in the name of Hitachi Seisaki Sho Kyowa Hakko Industry Co. and published on June 6, 1972, The direct current processes include the following:
(c) A process using a negative current.
(d) A process using a direct current intermittently.
However, the above described processes are not satis-factory commercially and leave room for improvement of - 10590S~

reproductivity of coloration and improvement of ease of treat-ment.
Namely, in these prior art processes, the formation of the oxide film and the adsorption of metal ions into the oxide film are affected by other electrolytic conditions, and it is relatively difficult to control the electrolytic conditlons efficiently and stably. Accordingly, when the adsorption efficiency of the metal ion is low or the stability of the oxide layer is poor, difficulties arise regarding the time requ1red for formation of the colored oxide layer.
With some metal salts, it is impossible to obtaln de-sired anodic oxidation coloration.
The present inventors have made various lnvestigations and found that a colored oxide film having an excellent uniformlty and a high reproductivity can be easily formed on an alumlnous material by effecting an electrolytic treatment by applying alternate positive and negative voltages to produce direct currents of opposite direction.
A previously-proposed method of producing a colored oxide coating on aluminum or aluminum alloy comprises~
passing a direct current through an electrolytic bath contalning metal ions and through a pair of electrodes immersed in the bath, a first of the electrodes comprising the aluminum or aluminum alloy, so that the first electrode forms the anode and receives an oxide coating, and reversing the direction of the current by providing across the electrodes a reverse voltage so that the first electrode forms the cathode, the metal ions diffusing to the electrode throughout the process and thereby becoming absorbed into the oxide coatlng of the alumlnum or aluminum alloy.

~059059 According to the present invention there lS provided a method of producing a colored oxide coating on alumlnum or an aluminum alloy, comprising formlng an oxide coating on the aluminum alloy by anodic oxidation, and providing the coated aluminum or aluminum alloy as a first of a pair of electrodes in an electrolytic bath containing metal ions, and alternately applying first and second voltages across the electrodes to produce first and second direct currents respectively flowlng in opposite directions, wherein the voltage across the electrodes when the first electrode is cathodic ls sufficiently large to causè electrolytic deposition of the metal ions on the oxide coating thereby coloring the coating.
The method of the invention may for example, be performed in the following manner.
An aluminous material to be treated is degreased and washed with water in a conventional manner, for example by de-greasing in an aqueous solution of NaOH, washing wlth water, neutralizing in an aqueous solution of HNO3 and then again washing with water.
Then, the thus treated aluminous materialiS used as either or both of the electrodes and an electrolysis treatment is carried out in an electrolytic bath of an aqueous solution of a metal salt of a mineral acid or an organic acid, or a mlneral acid or organic acid to which one or more metal salts have been added, at room temperature by means of a direct current, the polarity of which is alternated, In this case, the direction of flow of the direct current is reversed every 5 minutes or less and the voltage to be applled varies depending upon the metal salt present, although it is generally not more than 70 V, whereby a colored oxide film showing a color inherent to the above described added metal salt is formed on the alumin-ous material.
The method of the invention of coloring an alumlnous materlal can, for example, be performed as follows.
(1) Both the anode and cathode are made of an aluminous material and both the electrodes are colored simultaneously.
First, the aluminous materials are degreased and washed with water in a usual manner and the thus treated aluminous materials are immersed as the electrodes in an electrolytic bath containing a metal salt.
A direct current having an alternately changing polarity is applied between the aluminous material electrodes at a given frequency. In such a manner, oxide films having a color in-herent to the above described metal salt are formed on both electrodes.
Since the aluminous materials have been merely degreased ; and washed with water, an alumina film is formed on the aluminous material anode when the current is applied, while no alumina fllm is formed on the aluminous material cathode. When the current is reversed, the aluminous material whlch originally formed the anode now becomes the cathode, while the original cathode becomes the anode. When the polarity is changed in this manner, the alumina film on the oxidized aluminous material which now forms the cathode becomes colored by the function of the metal salt, while on the aluminous material which is now the anode, an alumlna film is formed. On restoration of the original direction of the current, this alumina film also becomes colored.
As described above, the formation-of the alumina film and the coloration with a metal salt are repeated alternately, whereby the colored films are formed on both the aluminous material electrodes.

,' ..~, ~

Since both the aluminous material electrodes can be subjected to a coloring oxidation treatment simultaneously, the productivity is improved and further it is merely necessary to effect the degreasing and washing with water of the aluminous material as a pre-treatment. The productivity is further improved from this point of view.
In this case, the voltages producing the forward and reverse currents are equal, the current densities are equal and the duration of the forward direct current is the same as the duration of the reverse direct current.

(2) Both the anode and cathode are of aluminous material, but on one of them a colored oxide film is formed and on the other a non-colored oxide film is formed during aach treatment.
In this process, even if the metal salt which colors the alumina film is one which by previously-proposed methods has deposited only with difficulty on the alumina film, the metal may be easily deposited and the coloration can be effected efficiently.
This process may be carried out by subjecting an alumin-ous material, after degreasing and washing with water, to aconventional anodic oxidation treatment to form an oxide film (A12O3) on the aluminous material. This anodically oxidized aluminous material is used as one of the electrodes, while the opposite electrode is an aluminous material which has simply been degreased and washed with water.
Then, both the electrodes are placed in an aqueous electrolytic bath consisting of an aqueous solution of a metal salt of a mineral or organic acid, or an aqueous solution of an acid to which has been added a metal salt, at room temperature.
A voltage is then applied to produce a direct current, and the 1059059 `
polarity is periodically reversed. The voltages and currents are selected so that when the already-coated aluminous material is the cathode the current is sufficient to provide electrolytic deposition of the metal ions on the oxide coating, but the reverse current is considerably smaller so that no electrolytic deposition of metal ions occurs on the originally-uncoated electrode when this electrode forms the cathode~ In this way, a colored oxide film is formed on the aluminous material pro-vided with a previously-formed oxide film and an oxide film is formed on the aluminous material which has been only degreased and washed with water. Then, the colored aluminous material is taken out of the electrolytic bath and a new aluminous material, which has been degreased and washed with water, is put in the electrolytic bath. This new electrode and the aluminous material electrode coated with an alumina layer are then subjected to the same electrolysis treatment as described above, the voltages and currents again being selected so that when the already-coated aluminous material is the cathode the current is sufficient to provide electrolytic deposition of the metal ions on the coating, the reverse current being considerably smaller. The aluminous material coated with the alumina layer in the earlier process thus becomes colored.
In the above described process (2), one of the electrodes has been previously subjected to an anodic oxidation. However, it is possible to carry out a similar process even if the alumin-ou~ material to be used as the electrodes has not been separately subjected to an anodic oxidation.
For example, in one embodiment, aluminous materials which have been degreased and washed with water are arranged as the electrodes in an electrolytic bath to which a metal salt lOS9059 has been added. Then, a direct current is applied, its polarity being periodically reversed. In this case, the current ln one direction is large and the current in the opposite direction is small, in order that the metal is not deposited on the aluminous material and that the alumina film is formed on only one of the aluminous material electrodes.
After the oxide film is formed on one of the aluminous material electrodes, the anodic oxidation may be repeated for the other electrode in the same manner, during which the already-formed oxide film on the first electrode becomes colored byelectrolytic deposition of the metal ions.

(3) As one electrode, useis made of an aluminous material whereon an alumina film has been previously formed and as the other electrode, use is made of a carbonaceous or other material, and a direct current which changes polarity alternately is applied.
An aluminous material which has been already degreased and washed with water is subjected to a conventional anodic oxidation treatment by means of, for example, an aqueous solution of sulfuric acid, to form a porous oxide film on the surface of the aluminous material.
The aluminous material coated with alumina and a car-bonaceous material are used as electrodes under a periodi-cally-reversing direct current, whereby the oxide film on the surface of the aluminous material becomes colored.
In the case described, a carbonaceous material is used as the other electrode, but alternatively the other electrode may be a previously-anodic-oxidized aluminous material. That is, both the electrodes may be of aluminous material having an oxide coating, in which case the coatings on both electrodes become colored.

lOS90S9

(4) As one electrode, use is made of an aluminous materlal which has been degreased and washed with water and not coated with alumina film, and as the other electrode, use lS made of a - different material,for example a carbonaceous material.
In this case, first a direct current which is large when the aluminous material is the anode and small when the aluminous material is the cathode is alternately applied in an electrolytic bath containing a metal salt as in the above des-cribed processes tl) - (3) to form an alumina film on the alumin-ous material. Then a direct current which reverses direction at predetermined intervals and which is small when the coated aluminous material is anodic and large when the coated aluminous material is cathodic is applied in the same bath as described above to form a colored oxide film on the aluminous material.
As mentioned above, the methods of the present lnvention can be carried out as in the above described exemplary processes (1) - (4).
The effects obtained by the present invention are as follows.
In previously-proposed coloring processes using a metal salt, a porous oxide film has first been formed on an aluminous material by anodic oxidation and then a metal oxide is deposited on the oxide film by means of an alternating current. Accord-ingly, an oxide film has been previously formed by direct current and then the coloration is made by a metal salt by means of an alternating current.
By using the method of the present invention, however, the formation of the oxide film and the coloration owlng to a metal salt can be alternately or simultaneously effected by means of a direct current which changes polarity alternately.

For example, when aluminous material is used for both electrodes, an oxide film is formed on the aluminous material which acts as the anode, and during application of reverse current, metal ions are adsorbed on the oxide film. The current is a direct current, so that the changing time and the voltage to be applied can easily be established and the aluminous material can be colored satisfactorily.
Coloration by the embodiments of the method of the present invention is effective in the following cases:
(1) When the metal salts which have previously been deposited only with difficulty on the oxide film are used; and (2) When the coloring electrolysis time is reduced.
The direction of the direct current is preferably re-versed every S minutes or less. If the current when the first electrode is anodic is applied for longer than 5 minutes the degree of coloration of the oxide coating on the first electrode is not improved and this is not advantageous economically, and if the current when the electrode is cathodic is applied for longer than 5 minutes a redissolution and separation of the oxide film from the aluminous material can occur, so that the formation of the colored oxide film is retarded, Embodiments of the invention will now be described by way of illustration in the following Examples, with reference to the accompanying drawings, wherein:
Figure 1 shows the wave shape and polarity of the direct current at each of the electrodes used in Example l; and Figure 2 shows the wave shape of the direct current at the aluminum alloy electrode used in Example 4.

_ g _ ~059059 Example l Aluminum alloy 1100 was degreased by immersing in an 8.0~ NaOH aqueous solution at 60C for 30 seconds and washed with water. The alloy was further immersed ln a 10~ HNO3 aqueous solution at room temperature for 20 seconds to effect neutralization, and was then washed with water.
The thus treated aluminum alloy was used as both anode and cathode. The electrodes were subjected alternately to a positive direct current and a negative direct current at an alternating time of 5 seconds for 30 minutes in an aqueous solution-containing 12.0% by weight of H2SO4 and 0.01% by weight of HAuCl4.~H2O at room temperature to effect electrolysis of the aluminum alloy. In this case, the voltage of the positive and negative direct currents was 17 V, and the current density thereof was 2 A/dm2. As a result, a light reddish purple oxide film was formed on the aluminum alloy.
Another electrolysis was effected for 60 minutes under the same conditions as described above to form a deep reddish purple oxide film having a thickness of 10 ~ .
Figure l shows the treating conditions in thls Example l.
Example 2 Aluminum alloy 6063 was degreased by immersing in an 8.0% NaOH aqueous solution at 60C for 3 minutes, and washed with water~ Then, the alloy was immersed in a 10% HNO3 aqueous solution at room temperature for 30 seconds to effect neutraliza-tion, and was then washed with water.
The thus treated aluminum alloy was used as both anode and cathode. The electrodes were subjected alternately to a positive direct current and a negative direct current at an ,-~.. , f ~059059 alternating time of 30 seconds for 60 minutes in an aqueous solution containing 15.0~ by weight of H2SO4 and 0.0025% by weight of AgNO3 at room temperature to effect electrolysis. In this case, the voltage of the positive and negative direct currents was 15 V, and the current density thereof was 1.5 A/dm2.
As the result, a uniform yellowish brown oxide film havlng a thickness of 7.5 ~ was formed on the aluminum alloy.
Example 3 The same aluminum alloy as used in Example 1 was de-greased and washed with water in the same manner as described in Example 1 and was used as both anode and cathode. The electrodes were subjected alternately to a positive direct current and a negative current at an alternating time of 10 seconds for 60 minutes in an aqueous solution containing 5.0~ by weight of C2H2O4 and 0.5% by weight of Na2SeO3 at room temperature to effect electrolysis. In this case, the voltage of the positive and negative direct currents was 50 V and the current density thereof was 2 A/dm2. As the result, a uniform orange oxide film having a thic~ness of 8.0/~ was formed on the aluminum alloy.
Example 4 The same aluminum alloy as used in Example 1 was de-greased and washed with water in the same manner as described in Example 1. The thus treated aluminum alloy was used as one electrode and carbon having a surface area of 2 dm2 was used as the other electrode. The aluminum alloy was subjected to electro-lysis in an aqueous solution containlng 15% by weight of H2SO4 and lo 0~ by weight of SnSO4 at room temperature in the following manner. In a first stage, the aluminum alloy electrode was subjected to a positive DC voltage of 14 V at a current density of 1 A/dm2 for 10 seconds and then subjected to a negatlve DC

r ~059059 voltage of 12 V at a current density of 1.5 A/dm2 for 2 seconds, and such steps were repeated for 30 minutes as shown in Figure 2a. Then, in a second stage, electrolysis was continued for 10 minutes at a positive direct current of 5 V and an alternating time of 2 seconds and at a negative direct current of 14 V and an alternating time of 2 seconds as shown in Figure 2b. After the first stage, a light amber-colored oxide film was formed on the aluminum alloy, and after the second stage, a deep amber-~ colored oxide film was formed on the aluminum alloy.
Example 5 The same aluminum alloy as used in Example 2, which had been degreased and washed with water in the same manner as des-cribed in Example 2, was used as an anode and subjected to a conventional anodic oxidation for 30 minutes in an aqueous solu-tion containing 15.0% by weight of H2SO4 to form a porous oxide film on the aluminum alloy.
Then, the thus treated aluminum alloy was used as one electrode, and carbon was used as the other electrode, and electro~-tic treatmentof the aluminum alloy was effected in an aqueous solution containing 10% by weight of H2SO4 and 0.5% by weight of SnSO4 a~ room temperature, in the following manner. The aluminum alloy electrode was subjected to a positive DC voltage of 3 V at a current density of not more than 0.1 A/dm2 for 2 seconds, and was then subjected to a negative DC voltage of 15 V at a current density of 1 A/dm2 for 10 seconds, and such steps were repeated for 30 minutes. As a result, a light amber-coloured oxide film was formed on the aluminum alloy after 2 minute treatment, a yellowish brown oxide film was formed after 5 minute treatment, a brown oxide film was formed after 10 minute treatment and a black oxide film was formed after 30 minute treatment.

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~059059 When the above described aluminum alloy coated with the porous oxide film was used as the cathode in electrolysis (-15 V, 1 A/dm2) in the electrolytic bath, the oxide film was removed within 2-3 minutes. Therefore, it was confirmed that an electrolytic treatment only by the negative current affects adversely the formation of a colored oxide film.
Example 6 The same aluminum alloy as used in Example 1, which was degreased and washed with water in the same manner as described in Example 1, was used as an anode, and subjected to an anodic oxidation in the same manner as described in Example 5 to form a porous oxide film on the aluminum alloy.
Then, the thus treated aluminum alloy was used as one electrode, and carbon was used as the other electrode, andelectroly-tic treatment of the aluminum alloy was effected in an aqueous solution containing 10.0% by weight of H2SO4 and 1.0% by weight of CuSO4 at room temperature in the following manner. In the positive direct current the applied voltage was 5 V and the current density was 0.2 A/dm2, and in the negative direct current the applied voltage was 25 V and the current density was 2.5 A/dm2. The alternating time was 2 seconds and the electrolysis time was 15 minutes. A light reddish purple oxide film was formed on the aluminum alloy after 3 minutes and a brown oxide film was formed after 15 minutes.
Example 7 The same aluminum alloy as used in Example 1 was de-greased and washed with water in the same manner as described in Example 1 and the thus treated alloy was used to form both anode and cathode. 10% by weight of H2SO4, 0.005% by weight of HAu.C14.4H2O and 0.01~ by weight of Ag2SO4 were added to water ~ . , i: .

lOS9OS9 and the formed silver chloride was filtered off, the filtrate then being used as an electrolytic bath. The electrodes were subjected alternately to a positive direct current and a negative direct current at an alternating time of 5 seconds for 60 minutes in the electrolytic bath at room temperature to effect electroly-sis. In this case, the voltage of the positive and negative direct currents was 18 V and the current density thereof was 1.5 A/dm2. As a result, a reddish brown oxide film having a thickness of 8.0~ was formed on the aluminum alloy, and it was confirmed that a colored oxide film could be obtained by~means of a mixture of metal salts.
_ample_ 8 Aluminum alloy 1100 or 6063 was degreased and washed with water in a conventional manner. The alloy was used as an anode and subjected to an anodic oxidation for 30 minutes in an aqueous solution of a sulfuric acid to form an alumina film having a ~thickness of about 7~X on the alloy. Then, the aluminum alloy bearing the oxide film was used as one electrode and the same aluminum alloy, which had however only been degreased and washed with water, was used as the other electrode, and electrolysis was effected under the conditions shown in Table 1. As a result, the aluminum alloy having the previously formed oxlde film was colored as shown in Table 1, whlle an oxide film was formed on the aluminum alloy which had been only degreased and washed with water. The colored aluminum alloy was removed from .he electro-lytic bath, and replaced by an aluminum alloy which had been de-greased and washed with water. Electrolysis was made then performed as shown in Table 1. The same colored oxide film as that of the removed aluminum alloy was formed on the aluminum alloy on which the oxide film had already been formed, and an oxide film on the new electrode of the aluminum alloy which had been only degreased and washed with water.

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_~ ,. _l ~D ~ ~ ~ ~ , ~ z Example 9 -Aluminum alloy 6063 was degreased and washed with water in a conventional manner and used as anode and cathode. A two stage electrolysis treatment was effected in one electrolytic bath by applying a positive direct current and a negative direct current alternately to the electrodes under the conditions shown below.
As a result, a colored oxide film was formed on one aluminum alloy electrode at the same time as an oxide film was-formed on the other.
10 1. Composition of electrolytic bath: -Base solution: H2SO4 15% by weight Added metal Salt: SnSO4 1.0% by weight 2. Electrolysis condition:
a. First stage electrolysis treatment:

Alternating Current Electrolysis Voltage time density -time (V) - (Sec.) (A/dm2) (min.) (+) 19 5 2 ) 50 (-) 19 5 2 In the first stage electrolysis treatment, oxide films were formed on both the aluminum alloy electrodes.
b. Second stage electrolysis treatment:
The above treated aluminum alloys were used as anode and cathode and successively subjected to a second stage treatment in the same electrolytic bath under the following conditions.

Alternatlng Current Electrolysls Voltage time denslty time (V) (Sec.) (A/dm2) (mln.) . _ (+) 8 2 0.2 ) 30 (-) 19 8 2-3 In the second stage electrolysis treatment, the oxide film formed on one of the aluminum alloys was colored yellowish brown while the oxide film formed on another aluminum alloy in the first stage electrolysis treatment maintained its original thickness.
Accordingly, the following treatment was able to be effected in this Example 9 similarly to Example 8. When the colored aluminum alloy was removed from the electrolytic bath, and an electrolytic treatment was effected in the same electrolytic bath under the same conditions as described above by introducing a new electrode of the aluminum alloy, which had been only de-greased and washed with water, to act with the aluminum alloy remaining in bath, on which the oxide film had been already formed in the above procedure. An oxide film was formed on the new aluminum alloy, and on the other aluminum alloy the film already formed became colored yellowish brown. In this way aluminum alloy was used as both electrodes in one electrolytic bath whereby an oxide film was formed on the aluminum alloy and the oxide film became colored alternately.
As described above, the present invention has the following merits.
1. Since electrolytic treatment of aluminous material is effected by applying alternately positive and negative direct currents to the material, a stable oxide film can be formed on one electrode of the material and at the same time metal of the added metal salt can be deposited efficiently on an oxide film of the other electrode. Accordingly, uniformly colored oxide films can be obtained easily and inexpensively with high reproductivity.
2. The thickness of the oxide film layer and the depth of color can be varied according to the requirements of users by ,, il , selecting appropriate values of the duration of the current in each direction, and the voltage current density of the current in each direction.
3. Aluminous material to be electrolytically treated can be used as one electrode or as both electrodes. Particularly, when aluminous materials are used as both electrodes, colored oxide films can be formed inexpensively with a high productivity.
4. Metal salts can be added to base solution singly or in admixture. Accordingly,_complicated color tones which cannot be obtained by conventional methods can be obtained.
Moreover, even when a metal salt which, in previously-proposed methods, forms deposits with difficulty on the oxide film is added to the base solution, the metal can be deposited with a high efficiency by the present method.

5. Electrolytic treatment of aluminous material can be effected at both electrodes, whereby formation of oxide film on the aluminous material and coloration of the oxide film can be effected alternately in one electrolytic bath.

6. Stable colored oxide film can be obtained with a high reproductivity. Even when a metal salt which forms deposits with difficulty is used, a stable colored oxide film can be obtained.
Moreover, the color tone of colored oxide films can be more complex.

7. The treatment described in the above item 5 can be effected efficiently and inexpensively on a commercial scale.

'.~

Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A method of producing a colored oxide coating on aluminum or aluminum alloy, comprising forming an oxide coating on the aluminum or aluminum alloy by anodic oxidation, and providing the coated aluminum or aluminum alloy as a first of a pair of electrodes and aluminum, aluminum alloy or carbonaceous material as a second electrode in an electrolytic bath containing metal ions and alternately applying first and second voltages across the electrodes to produce first and second direct currents respectively flowing in opposite directions, wherein the voltage across the electrodes when the first electrode is cathodic is applied at intervals of less than five minutes in such a manner that the negative charge applied to the first electrode is equal to or larger than the positive charge applied thereto when the first electrode is anodic to cause electrolytic deposition of the metal ions on the oxide coating, thereby coloring the coating.
2. A method as claimed in claim 1, wherein the formation of the oxide coating on the first electrode and the coloration of the coating occur successively in the same bath and with the same electrodes.
3. A method as claimed in claim 2, wherein the second of the pair of electrodes is aluminum or aluminum alloy, and the voltage across the electrodes when the second electrode is anodic is sufficiently large to cause formation of oxide on the second electrode and the voltage across the electrodes when the second cathode is cathodic is sufficiently large to cause electrolytic deposition of the metal ions on the thus formed oxide coating of the second electrode so that both electrodes receive a colored oxide coating.
4. A method as claimed in claim 2, wherein the anodic oxidation is performed by periodically reversing the direction of the current, and during said anodic oxidation the current flowing when the first electrode is cathodic is smaller than the current flowing when the first electrode is anodic.
5. A method as claimed in claim 4, wherein after formation of the oxide coating the current flowing when the first electrode is cathodic is greater than the current flowing when the first electrode is anodic so that the oxide coating formed on the first electrode becomes colored.
6. A method as claimed in claim 1, wherein neither the first nor the second voltage across the electrodes exceeds 70 V.
CA172,956A 1972-06-06 1973-05-31 Producing a coloured oxide on an article of aluminium or aluminium alloy Expired CA1059059A (en)

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CA172,956A Expired CA1059059A (en) 1972-06-06 1973-05-31 Producing a coloured oxide on an article of aluminium or aluminium alloy

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US (1) US3892636A (en)
AU (1) AU465572B2 (en)
CA (1) CA1059059A (en)
CH (1) CH581705A5 (en)
DE (1) DE2328538A1 (en)
GB (1) GB1438383A (en)

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JPS5425898B2 (en) * 1974-08-29 1979-08-31
JPS5512196B2 (en) * 1975-08-27 1980-03-31
US4147598A (en) * 1975-08-27 1979-04-03 Riken Keikinzoku Kogyo Kabushiki Kaisha Method for producing colored anodic oxide films on aluminum based alloy materials
GB1548689A (en) * 1975-11-06 1979-07-18 Nippon Light Metal Res Labor Process for electrograining aluminum substrates for lithographic printing
ES482210A0 (en) * 1979-07-04 1982-08-01 Process for the electrolytic coloration of a-nodized aluminum.
JPS5852038B2 (en) * 1980-03-26 1983-11-19 Nippon Keikinzoku Sogo Kenkyusho Kk
ES490784A0 (en) * 1980-04-22 1981-02-16 Empresa Nacional Aluminio Process to electrolytically color aluminum and its alloys
AU533310B2 (en) * 1980-12-27 1983-11-17 K.K. Chiyoda Chemically producing anodic oxidation coat on al or al alloy
DE3127330C2 (en) * 1981-07-10 1990-02-01 United Chemi-Con, Inc., Rosemont, Ill., Us
US4517059A (en) * 1981-07-31 1985-05-14 The Boeing Company Automated alternating polarity direct current pulse electrolytic processing of metals
US4666567A (en) * 1981-07-31 1987-05-19 The Boeing Company Automated alternating polarity pulse electrolytic processing of electrically conductive substances
US4478689A (en) * 1981-07-31 1984-10-23 The Boeing Company Automated alternating polarity direct current pulse electrolytic processing of metals
GB9825043D0 (en) * 1998-11-16 1999-01-13 Agfa Gevaert Ltd Production of support for lithographic printing plate
CN1181228C (en) * 2000-10-25 2004-12-22 有限会社创研 Aluminium or its alloy surface treatment
US20100143622A1 (en) * 2006-11-23 2010-06-10 Anox B.V. Process for providing aluminium cookware with a copper coating
US8101059B2 (en) * 2008-02-28 2012-01-24 Corning Incorporated Methods of making titania nanostructures
JP5691135B2 (en) * 2009-03-31 2015-04-01 スズキ株式会社 Anodized film and anodizing method
AR102806A1 (en) * 2015-07-21 2017-03-29 Consejo Nac De Investig Científicas Y Técnicas (Conicet) Method of anodizing aluminum structural color by forming photonic crystals by current pulses

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US2930741A (en) * 1960-03-29 Electrolytic capacitors
US3382160A (en) * 1960-03-31 1968-05-07 Asada Tahei Process for inorganically coloring aluminum
DE1948552B2 (en) * 1968-09-26 1971-04-22 A process for the electrolytic production of dyed oxide layers on aluminum
FR1596808A (en) * 1968-12-06 1970-06-22
US3654100A (en) * 1969-05-31 1972-04-04 Riken Almite Industry Co Ltd Process of forming colored anode oxidized film on aluminummaterial
US3639221A (en) * 1969-12-22 1972-02-01 Kaiser Aluminium Chem Corp Process for integral color anodizing
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US3773631A (en) * 1970-10-16 1973-11-20 Blasberg Gmbh & Co Kg Friedr Aqueous electrolytic bath for coloring anodic oxide layers on aluminum and aluminum alloy substrates and process for coloring said substrates
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US3751350A (en) * 1972-03-03 1973-08-07 Aiden Kk Process for coloring an aluminum anodic oxide film

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US3892636A (en) 1975-07-01
DE2328538A1 (en) 1973-12-20
CH581705A5 (en) 1976-11-15
GB1438383A (en) 1976-06-03
AU465572B2 (en) 1975-10-02
AU5641373A (en) 1974-12-05
CA1059059A1 (en)

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