CA1060838A - Process for continuous electrolytic coloring of aluminum or aluminum base alloy strip and wire - Google Patents
Process for continuous electrolytic coloring of aluminum or aluminum base alloy strip and wireInfo
- Publication number
- CA1060838A CA1060838A CA239,988A CA239988A CA1060838A CA 1060838 A CA1060838 A CA 1060838A CA 239988 A CA239988 A CA 239988A CA 1060838 A CA1060838 A CA 1060838A
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- Prior art keywords
- colouring
- wire
- aluminum
- strip
- bath
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/04—Anodisation of aluminium or alloys based thereon
- C25D11/18—After-treatment, e.g. pore-sealing
- C25D11/20—Electrolytic after-treatment
- C25D11/22—Electrolytic after-treatment for colouring layers
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electroplating Methods And Accessories (AREA)
- Printing Plates And Materials Therefor (AREA)
- Chemical Or Physical Treatment Of Fibers (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An improved process for electrolytically colouring an anodically oxidized aluminum or aluminum base alloy strip or wire which comprises, while continuously travelling the strip or wire through an electrolytic colouring means, subjecting the anodically oxidized strip or wire as a cathode to direct current electrolysis using an electrolytic colouring means comprising at least one hollow body having an opening for con-tinuously supplying a colouring bath onto the surface of the oxidized strip or wire and an electrode acting as an anode therein, and continuously supplying the colouring bath through the opening of the hollow body onto the surface of the oxidized strip or wire.
An improved process for electrolytically colouring an anodically oxidized aluminum or aluminum base alloy strip or wire which comprises, while continuously travelling the strip or wire through an electrolytic colouring means, subjecting the anodically oxidized strip or wire as a cathode to direct current electrolysis using an electrolytic colouring means comprising at least one hollow body having an opening for con-tinuously supplying a colouring bath onto the surface of the oxidized strip or wire and an electrode acting as an anode therein, and continuously supplying the colouring bath through the opening of the hollow body onto the surface of the oxidized strip or wire.
Description
BACKGROUND OF THE INVENTION
1. Field of the I_v ti.on This invention rela-tes to a process for the continuous electrolytic colouring of an article of aluminum or an aluminum base alloy (hereinafter referred to aluminum) in a windable shape, such as an aluminum strip or wire.
1. Field of the I_v ti.on This invention rela-tes to a process for the continuous electrolytic colouring of an article of aluminum or an aluminum base alloy (hereinafter referred to aluminum) in a windable shape, such as an aluminum strip or wire.
2. Descri~tion of the Prior Art Various processes for the electrolytic colouring of 0 aluminum comprising subjecting aluminum which has previously been anodically oxidized to electrolysis in an electrolytic colouring bath comprlsing an aqueous solution of at least one nickel salt, cobalt salt, tin salt, iron salt, copper salt or selenious acid, the aluminum serving as an electrode, are well known in the art. These electrolytic colouring processes are known to be economically advantageous as they enable one to produce electrolytically coloured aluminum articles with ex-~ellent reproducibility which are uniform in colour. In addition, because of their excellent weatherability or fade resistance, the resulting electrolytically coloured aluminum generally can be used as structural materials such as extrusions, plates and the like.
Known electrolytic colouring processes can be classified as alternating current electrolysis processes as disclosed in U.S. Patent 3,382,160 or direct current electrolysis processes as disclosed in U.S. Patent 3,761,362, depending upon the kind of electric current which is passed through the electrolytic colouring bath.
The process disclosed in U.S. Patent 3,761,362 is characterized by the colouration of a previously anodized ~k 1C~60~33B
1 aluminum by subjecting the aluminum to a direct current elec-tro-lysis, with the aluminum as a cathode, in an electrolytic colouring bath comprising an aqueous solution containing at least one nickel salt, cobalt salt, tin salt, iron salt, copper salt or selenious acid.
In this direct current electrolysis, the composition of the electrolytic colouring bath is suitably selected from the above-described components depending on the desired colour.
Generally, the colour formed on the surface of the aluminum is ~0 bronze when a nickel salt is used, reddish-brown when a copper salt is used, bronze to black when a tin salt is used, bronze when a cobalt salt is used, yellow when an iron salt is used, and yellow to reddish-orange when selenious acid is used.
The above direct current electrolytic colouring process can be carried out in a continuous manner which is advantageous in that electrolytically coloured aluminum can be obtained economically by continuously anodically oxidizing a windable aluminum article such as strips, wires and the like, and then subjecting the resulting anodically oxidized aluminum article to a direct.current electrolytic colouring process, followed by conventional final treatments such as a sealing treatment or various coating treatments. However, when the electrolytic colouring process is effected in a conventional electrolytic cell containing an electrolytic colouring bath by continuously supplying aluminum as a cathode from one end of the electrolytic colouring cell which is provided with an anode on an inside wall or on the bottom of the cell and with agitation means for the colouring bath, e.g., by injecting air ~r the colouring bath into the cell, it is very difficult to
Known electrolytic colouring processes can be classified as alternating current electrolysis processes as disclosed in U.S. Patent 3,382,160 or direct current electrolysis processes as disclosed in U.S. Patent 3,761,362, depending upon the kind of electric current which is passed through the electrolytic colouring bath.
The process disclosed in U.S. Patent 3,761,362 is characterized by the colouration of a previously anodized ~k 1C~60~33B
1 aluminum by subjecting the aluminum to a direct current elec-tro-lysis, with the aluminum as a cathode, in an electrolytic colouring bath comprising an aqueous solution containing at least one nickel salt, cobalt salt, tin salt, iron salt, copper salt or selenious acid.
In this direct current electrolysis, the composition of the electrolytic colouring bath is suitably selected from the above-described components depending on the desired colour.
Generally, the colour formed on the surface of the aluminum is ~0 bronze when a nickel salt is used, reddish-brown when a copper salt is used, bronze to black when a tin salt is used, bronze when a cobalt salt is used, yellow when an iron salt is used, and yellow to reddish-orange when selenious acid is used.
The above direct current electrolytic colouring process can be carried out in a continuous manner which is advantageous in that electrolytically coloured aluminum can be obtained economically by continuously anodically oxidizing a windable aluminum article such as strips, wires and the like, and then subjecting the resulting anodically oxidized aluminum article to a direct.current electrolytic colouring process, followed by conventional final treatments such as a sealing treatment or various coating treatments. However, when the electrolytic colouring process is effected in a conventional electrolytic cell containing an electrolytic colouring bath by continuously supplying aluminum as a cathode from one end of the electrolytic colouring cell which is provided with an anode on an inside wall or on the bottom of the cell and with agitation means for the colouring bath, e.g., by injecting air ~r the colouring bath into the cell, it is very difficult to
3~ obtain a uniformly coloured aluminum in a stable manner. That is, ~060838 1 satisfactory colourin~ is difficult to conduct due to the problems hereinafter described, whereby the resulting colour tone tends to be non-uniform, for example, a stripe-pattern com-prising a deeply-coloured portion and an unat-tractive lightly-coloured portion results, and the electrolytically coloured film on the aluminum tends to be partially spalled. These phenomina are frequently observed with an electrolytic colouring proces5 conducted on a large industrial scale, and are liable to occur as the travelling speed of the aluminum passing through the colouring bath increases and the electric current applied to the colouring bath increases.
SUMMARY OF THE INVENTION
An object of this invention is to provide a direct current process for the continuous electrolytic colouring of a windable aluminum strip or wire.
Another object of this invention is to provide a process for producing an uniformly coloured aluminum s-trip or wire in a stable manner by a direct current electrolytic colouring process which eliminates the problems associated with con-~0 ventional processes such as irregular stripe-pa-ttern colouration and spalling of the electrolytically coloured oxide film on the aluminum strip or wire.
As a result of studies on processes for the con-tinuous electrolytic colouring of aluminum, it was found that the above-described disadvantages associated with conventional processes are due to the fact that during electrolytic colouring the electric current is partially concentra-ted, in particular, at portions of the aluminum which come into contact with the colouring bath, and that hydrogen gas generated on the surface of the aluminum as a cathode is difficult to completely remove.
~060~
1 The present invention provides an improved process for electrolytically colouring an anodically oxidized aluminum strip or wire which comprises, while continuously travelling the strip or wire through an electrolytic colouring means, subjecting the anodically oxidized aluminum strip or wire as a cathode to direct current electrolysis using an electrolytic colouring means comprising at least one hollow body having an opening for con-tinuously supplying a colouring bath onto the surface of the aluminum strip or wire and an electrode acting as an anode in the hollow body, and continuously supplying the colouring bath through the opening of the hollow body onto the surface of the aluminum strip or wire.
BRIEF DESCRIPTION OF ~HE DRAWINGS
Figures 1 and 2 are schematic drawings illustrating embodiments of an electrolytic colouring system in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The anodic oxidation carried out prior to the electro-lytic colouring treatment of this invention is usually carriedout in an anodic oxidation bath comprising an aqueous solution of about 10 to 55% sulfuric acid with a current density of from 3 to 50 A/dm2, but, if desired, the anodic oxidation bath may further contain a small amount of a salt such as magnesium chloride, sodium sulfate, magnesium sulfate, sodium chloride, etc.; a carboxylic acid; an organic sulfonic acid; and/or an amine. The electric current used for the anodic oxidation can be a direct current or direct and alternating superposed currents.
The direct current electrolysis for colouring of an 106~838 1 aluminum strip or wire according to the present invention can be carried out using conventional electrolytic colouring baths.
The main component of the electrolytic colouring bath used herein is one or more water-soluble metal salts such as water-soluble nickel salts (such as nickel sulfate, nickel chloride, nickel acetate and the like~, copper salts (such as cupric sulfate and the like), tin salts (such as stannous chloride, stannous sulfate and the like), cobalt salts (such as cobalk sulfate, cobalt acetate and the like), iron salts (such as ferrous sulfate and the like), like mekal salts, and selenious acid. Further, if desired, the electrolytic bath may contain a suitable amount of boric acid or sulfuric acid to control the pH and the electric conductivity of the bath. For example when the main component is nickel sulfate, ~oric acid is often used in combination with nickel sulfate, with both components being capable of use over a relatively wide range of con-centrations, for example, about lS to 100 g/liter of nickel sulfate and about 10 to 50 g/liter of boric acid producing a superior coloured oxidè film.
The term ~Idirect current" as used herein means an electric current which always flows in a fixed direction, as is well known. Therefore~ the direct current is not limited by - the wave form thereof and it includes all electric currents which have a wave form periodically changing in current strength, so long as the direction of the current flow is no-t changed.
The current density used in the electrolytic colouring process for this invention can range from about 0.05 to 3.0 ~/dm , but a range of 0.1 to 2.0 A/dm2 is preferred from an operational point of view. Further, bath temperatures in the vicinity of room temperature are sufficient, but a temperature of from about 1~i0~3~3 1 10 to 40 can also be used for colouring.
The period during which time the colouring phenomenon occurs, i.e., the actual colouring time, varies depending upon the distance between the surface of the aluminum strip or wire and the opening of the hollow body employed in the present invention, but is generally adjusted to be less than about 30 seconds, preferably from 2 to 15 seconds. The colouring time used herein means the actual time when the aluminum strip or wire contacts the colouring bath and the colouring phenomenon actually occurs. Therefore, the colouring time is not always identical with the contact time of the aluminum strip or wire with the colouring bath That is, the region where the colouring phenomenon occurs is not determined with reference to the length of aluminum strip or wire contacting with the colouring bath, rather, it is determined by the region of current distribution having the specified current density through the opening of the hollow body from the anode into the surface(s~ of the aluminum strip or wire treated. The time when the aluminum strip or wire passes through this region corresponds to the colouring time as defined above.
The narrower the distance between the lower portion of tha opening provided in the hollow body and the surface(s) of the aluminum strip or wire to be treated, the easier the colouring operation is. The minimum distance can be easily determined by a simple pre-experiment from the viewpoint of the size of the apparatus used, the bending degree of the aluminum strip or wire, the uniformity of colouring, etc. The maximum distance is not particularly limited, but is preferably controlled to be less than about 100 mm from the viewpoint of the electric power consumed.
The amount of the colouring bath which is supplied to the surface(s) of aluminum strip or wire via the opening of ~6083~
hollow body is not particularly limited, and can generally be varied dependiny upon the degree of desorption of hydrogen gas generated on the surface(s) of the aluminum strip or wire during the electrolysis step.
The process of this invention will be further illus trated in greater detail by reference to the accompanying drawings.
Figure 1 is a schematic sectional side view of an embodiment of the apparatus used in the process of this invention. In Figure 1, 1 is an aluminum strip or wire which has t previously been anodically oxidized by a conventional process~
This anodically oxidized aluminum strip or wire 1 is used as a cathode by applying electric current using the liquid electric supply method or the roll electric supply method. 2 is an electrolytic colouring cell containing a colouring bath 3 for obtaining the desired colour as earlier described. 4 represents a pair of rollers for travelling the aluminum strip or wire to be electrolytically coloured, which rollers can be provided at any convenient positions. 5 is a heat exchanger for con-trolling the temperature of the colouring bath. 6 is a pump for ~ supplying the colouring bath to an electrolytic colouring means comprising a hollow body 7 while circulating the colouring bath. The hollow body 7 which characterizes this invention is provided with an anode 8 inside the cavity of the hollow body, which anode 8 is electrically insulated from the hollow body, and has an opening 9 for continuously supplying the colouring bath onto the surface of the travelling aluminum strip or wire and has at least one inlet 10 for introducing the circulating colouring bath into the hollow body 7.
In Figure 1, two hollow bodies are positioned facing the upper surface and the lower surface of the aluminum strip or wire 1, respectively, but this pair of hollow bodies can be ~060831~
1 modified so as to integrate the two hollow bodies into a single hollow body or, alternatively, two or more hollow bodies can be provided at each of the upper and lower surfaces of the alu~inum strip or wire to be electrolytically coloured.
In carrying out the process of this invention, the anodically oxidized aluminum strip or wire 1 is first thoroughly rinsed with water and then introduced by means o-f driving rollers, guide rollers or the like into the electrolytic colouring cell 2 where the aluminum strip or wire is brought into.contact with the colouring~bath 3. The aluminum strip or wire 1 further travels in the colouring bath and approaches the hollow bodies 7 where the aluminum strip or wire is to be electrolytically coloured. The colouring rate of the aluminum strip or wire increases as the aluminum strip or wire approaches the hollow bodies and decreases as the strip.or wire travels away from the hollow bodies. A
strip or wire which is completaly coloured finally emerges from the colouring bath.
Of course, during the above colouring procedure)direct~
current is passed through the colouring bath between the aluminum strip or wire as a cathode and the anode provided in the hollow body or bodies 7.
As described above, the characteristic feature of the present invention resides in that colouring occurs at areas where the aluminum strip or wire to be electrolytically coloured appro-aches close to the hollow bodies 7.
The hollow body 7 used in the present invention as the the electrolytic colouring means includes any type of hollow member which can be provided with an anode therein electrically insulated from other portions of the hollow body, and which has at least one inlet for introducing a colouring bath and an opening for supplying a colouring bath by flowing the same toward a travelling aluminum strip or wire disposed adjacent the bath supply opening. The hollow body can be of any shape, for example, 1~6~33~3 1 cylindrical or box-like. The opening in the hollow body is preferably a slit shape, the longitudina:l direction of the slit being perpendicular to the travelling direction of the aluminum strip or wire, but it may be of any shape so long as the opening is capable of flowing the colouring bath uniformly toward the travelling aluminum strip or wire.
The anode is also preferably arranged perpendicular to the travelling direction of the aluminum strip or wire,and is advantageously made from a material which is convenient for the maintenance of the colouring bath used, for example, a nickel plate when the colouring bath contains nickel ions. The amount of the colouring bath flowing or ejected through the opening can be controlled by liquid flow control means such as a valve, after pump 6.
The flow rate of the colouring bath and the slit width of the opening are not critical, and vary depending upon various parameters used in the process, but in large s/ le industrial apparatus it is preferred to use higher in-~ee~
rates and larger slit widths as the travelling rate of the aluminum strip or wire increases.
In another embodiment of the process of this invention, it is possible to electrolytically colour only one surface of an aluminum strip by, for example, using an apparatus as illustrated in Figure 2.
Referring now to Figure 2, members 1 to 10 have the same meanings as explained with reference to Figure 1, an~ the shape and the function of these members is the same as in Figure l; there are, however, two significant differences between the systems shown in Figures 1 and 2.
Firstly, aluminum strip 1 is not contacted with ~L~6~8 1 colouring bath 3 contained in colouring cell 2, but is contacted only with a colouring bath layer 12 formed on the surface of the travelling aluminum strip. When direct current is applied in this state between anode 8 and aluminum strip 1 while travelling the aluminum strip, an aluminum strip electrolytically coloured on only one surface (the surface which is contacted with the colouring bath layer 12) is obtained. Secondly, in this embodi-ment the colouring time can be adjusted by changing the distance between colouring-adjustment rollers 11 and 11', i.e., the longer the distance between the rollers, the longer the colouring time at constant rates of travel. Rollers 11 and 11' function only to adjust the length of the colouring bath layer 12, and can be made from a wide variety of materials, such as rubber, sponge, plastic and the l`ike. Rollers 11 and 11' may be eliminated i the rollers 4 are shifted to a position closer to each other so as to function as rollers 11 and 11'.
The characteristic feature of the embodiment of Figure 2 is that electrolytic colouring occurs only at the area i near the hollow body 7 a~d the colouring bath layer 12. Thus, a hollow body can be provided facing the lower surface of the aluminum strip to thereby electrolytically colour the lower surface of the aluminum strip, or the hollow body can be pro-vided facing both the upper and lower surfaces of the aluminum strip, thereby electrolytically colouring both surfaces o~
the aluminum strip. Further, it is possible to electrolytically colour the aluminum strip in special patterns, for example, in a stripe-pattern, by providing a particular type of hollow body.
For example, a stripe-pattern colouring in which deeply-coloured portions and lightly-coloured portions are parallel to the 106~38 travelling direction of the aluminum strip can be attained when the opening of one or more hollow bodies i5 partiall~ covered with an appropriate member, such as a rubber plate or sponye, and electrolytic colouring is conducted while setting the partiall~
covered hollow body or bodies close to the surface of the travelling aluminum stripO
In Figure 2, the hollow body 7 is provided at the upper surface of the aluminum strip, but as previously described, two or more hollow bodies can be provided at the upper and/or lower surface of the aluminum strip.
In the embodiment illustrated in Figure 2, the colouring bath sometimes tends to flow down to the edge portions of the lower surface of the aluminum strip, thereby partially colouring the edge portions. Such undesirable colouring can be prevented by increasing the flow rate of the colouring bath or by blowing pressurized air toward the lower surface of the al~inum strip.
~ he aluminum thus coloured is then washed with water and can then be subjected to a conventional sealing treatment `20 ~ various lacquer coating methods including electrodeposition, dipping and spraying, as are known in the art.
As will be apparent to one skilled in the art, when the electric polarity is reversed and an aqueous solution of sulfuric acid is used in place of the colouring bath in the embodiment shown in Figure 2, only one surface of the aluminum strip can be anodically oxidized; such as embodiment is not contemplated in the present invention.
As previously described, in accordance with the process of this invention, a stable, uniformly coloured aluminum strip or wire can be obtained without partial spalling of the 1~6l~8;3~3 ~
1 coloured film. Also, since the process of this invention makes it possible to electrolytically colour only one surface of an aluminum strip and, if desired, to colour an aluminum strip in a stripe-pattern, various coloured aluminum strips suitable for use in a wide variety of utilities can be obtained.
In addition, as a most significant feature of the process of this invention, anodically oxidized aluminum having a very thin anodic oxide film thereon, for example, an anodic oxide film having a thickness of 1 to 2 ~,which could not be effectively electrolytically coloured by conventional electrolytic colouring processes, can be coloured stably and uniformly by the process of this invention. The above fact indicates that electrolytically coloured strips and wires having an excellent resistance to weathering can be produced at low cost and, therefore, the effects brought about by the present invention are vexy important economically.
The present invention will be illustrated in further detail by reference to the following Examples~ but is not restricted thereto as the examples were conducted on a small ~ scale for purposes of illustration.
A coiled aluminum strip 65 mm (width) x 0.3 mm ~thick-ness) having an aluminum content of 99.2~ was mounted on the uncoiling means of an apparatus comprising an uncoiler, etching cel~, washing cell, current supplying cell, anodic oxidation cell, washing cell, electrolytic colouring cell, washing cell, seal-ing cell and a recoiler, and passed through the recited units in the order given. The apparatus used was substantially identical to that disclosed in Canadian Patent No. 1,032,106 filed March 6, 1974, except, of course, for the novel colouring .
~J . .
,., ~.
-` ~06083~
1 means of the present invention.
In the electrolytic colouring cell, the aluminum strip was immersed in a colouring bath and two hollow bodies were positioned ~acing both sur~aces of the aluminum strip, as shown in Figure 1. Each of the hol:Low bodies was in the form o~
a circular cylinder havlng a diameter of 30 mm and a length oE
lO0 mm. The hollow body was provided with a slit extending axially throughout the length thereof, the width of the slit beiny 1 mmO An anode plate of nickel was housed along the 1~ axis thereof, the dimensions of the anode plate being 20 ~m x 80 mm x 0.5 mm. The hollow bodies were disposed perpendicularly to the travelling direction of the strip, the distance between the strip and each hollow body being 1 m~. The aluminum strip was treated as described hereinafter.
The aluminum strip was introduced into the etching cell through the uncoiler at a rate of 20 cm/min, and contacted therein with a 10% aqueous sodium hydroxide solution at a bath temperature of 50C for one minute, and passed therethrough to the washing cell where the aluminum strip was passed through a water bath-The resulting strip was then introduced into the current supplying cell which contained a 30% aqueous sulfuric acid solution in which was disposed a carbon anode plate, wherein the aluminum strip was subjected to electrolysis at a current density o~ 2.0 A/dm2 at a bath temperature of 25 C for
SUMMARY OF THE INVENTION
An object of this invention is to provide a direct current process for the continuous electrolytic colouring of a windable aluminum strip or wire.
Another object of this invention is to provide a process for producing an uniformly coloured aluminum s-trip or wire in a stable manner by a direct current electrolytic colouring process which eliminates the problems associated with con-~0 ventional processes such as irregular stripe-pa-ttern colouration and spalling of the electrolytically coloured oxide film on the aluminum strip or wire.
As a result of studies on processes for the con-tinuous electrolytic colouring of aluminum, it was found that the above-described disadvantages associated with conventional processes are due to the fact that during electrolytic colouring the electric current is partially concentra-ted, in particular, at portions of the aluminum which come into contact with the colouring bath, and that hydrogen gas generated on the surface of the aluminum as a cathode is difficult to completely remove.
~060~
1 The present invention provides an improved process for electrolytically colouring an anodically oxidized aluminum strip or wire which comprises, while continuously travelling the strip or wire through an electrolytic colouring means, subjecting the anodically oxidized aluminum strip or wire as a cathode to direct current electrolysis using an electrolytic colouring means comprising at least one hollow body having an opening for con-tinuously supplying a colouring bath onto the surface of the aluminum strip or wire and an electrode acting as an anode in the hollow body, and continuously supplying the colouring bath through the opening of the hollow body onto the surface of the aluminum strip or wire.
BRIEF DESCRIPTION OF ~HE DRAWINGS
Figures 1 and 2 are schematic drawings illustrating embodiments of an electrolytic colouring system in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The anodic oxidation carried out prior to the electro-lytic colouring treatment of this invention is usually carriedout in an anodic oxidation bath comprising an aqueous solution of about 10 to 55% sulfuric acid with a current density of from 3 to 50 A/dm2, but, if desired, the anodic oxidation bath may further contain a small amount of a salt such as magnesium chloride, sodium sulfate, magnesium sulfate, sodium chloride, etc.; a carboxylic acid; an organic sulfonic acid; and/or an amine. The electric current used for the anodic oxidation can be a direct current or direct and alternating superposed currents.
The direct current electrolysis for colouring of an 106~838 1 aluminum strip or wire according to the present invention can be carried out using conventional electrolytic colouring baths.
The main component of the electrolytic colouring bath used herein is one or more water-soluble metal salts such as water-soluble nickel salts (such as nickel sulfate, nickel chloride, nickel acetate and the like~, copper salts (such as cupric sulfate and the like), tin salts (such as stannous chloride, stannous sulfate and the like), cobalt salts (such as cobalk sulfate, cobalt acetate and the like), iron salts (such as ferrous sulfate and the like), like mekal salts, and selenious acid. Further, if desired, the electrolytic bath may contain a suitable amount of boric acid or sulfuric acid to control the pH and the electric conductivity of the bath. For example when the main component is nickel sulfate, ~oric acid is often used in combination with nickel sulfate, with both components being capable of use over a relatively wide range of con-centrations, for example, about lS to 100 g/liter of nickel sulfate and about 10 to 50 g/liter of boric acid producing a superior coloured oxidè film.
The term ~Idirect current" as used herein means an electric current which always flows in a fixed direction, as is well known. Therefore~ the direct current is not limited by - the wave form thereof and it includes all electric currents which have a wave form periodically changing in current strength, so long as the direction of the current flow is no-t changed.
The current density used in the electrolytic colouring process for this invention can range from about 0.05 to 3.0 ~/dm , but a range of 0.1 to 2.0 A/dm2 is preferred from an operational point of view. Further, bath temperatures in the vicinity of room temperature are sufficient, but a temperature of from about 1~i0~3~3 1 10 to 40 can also be used for colouring.
The period during which time the colouring phenomenon occurs, i.e., the actual colouring time, varies depending upon the distance between the surface of the aluminum strip or wire and the opening of the hollow body employed in the present invention, but is generally adjusted to be less than about 30 seconds, preferably from 2 to 15 seconds. The colouring time used herein means the actual time when the aluminum strip or wire contacts the colouring bath and the colouring phenomenon actually occurs. Therefore, the colouring time is not always identical with the contact time of the aluminum strip or wire with the colouring bath That is, the region where the colouring phenomenon occurs is not determined with reference to the length of aluminum strip or wire contacting with the colouring bath, rather, it is determined by the region of current distribution having the specified current density through the opening of the hollow body from the anode into the surface(s~ of the aluminum strip or wire treated. The time when the aluminum strip or wire passes through this region corresponds to the colouring time as defined above.
The narrower the distance between the lower portion of tha opening provided in the hollow body and the surface(s) of the aluminum strip or wire to be treated, the easier the colouring operation is. The minimum distance can be easily determined by a simple pre-experiment from the viewpoint of the size of the apparatus used, the bending degree of the aluminum strip or wire, the uniformity of colouring, etc. The maximum distance is not particularly limited, but is preferably controlled to be less than about 100 mm from the viewpoint of the electric power consumed.
The amount of the colouring bath which is supplied to the surface(s) of aluminum strip or wire via the opening of ~6083~
hollow body is not particularly limited, and can generally be varied dependiny upon the degree of desorption of hydrogen gas generated on the surface(s) of the aluminum strip or wire during the electrolysis step.
The process of this invention will be further illus trated in greater detail by reference to the accompanying drawings.
Figure 1 is a schematic sectional side view of an embodiment of the apparatus used in the process of this invention. In Figure 1, 1 is an aluminum strip or wire which has t previously been anodically oxidized by a conventional process~
This anodically oxidized aluminum strip or wire 1 is used as a cathode by applying electric current using the liquid electric supply method or the roll electric supply method. 2 is an electrolytic colouring cell containing a colouring bath 3 for obtaining the desired colour as earlier described. 4 represents a pair of rollers for travelling the aluminum strip or wire to be electrolytically coloured, which rollers can be provided at any convenient positions. 5 is a heat exchanger for con-trolling the temperature of the colouring bath. 6 is a pump for ~ supplying the colouring bath to an electrolytic colouring means comprising a hollow body 7 while circulating the colouring bath. The hollow body 7 which characterizes this invention is provided with an anode 8 inside the cavity of the hollow body, which anode 8 is electrically insulated from the hollow body, and has an opening 9 for continuously supplying the colouring bath onto the surface of the travelling aluminum strip or wire and has at least one inlet 10 for introducing the circulating colouring bath into the hollow body 7.
In Figure 1, two hollow bodies are positioned facing the upper surface and the lower surface of the aluminum strip or wire 1, respectively, but this pair of hollow bodies can be ~060831~
1 modified so as to integrate the two hollow bodies into a single hollow body or, alternatively, two or more hollow bodies can be provided at each of the upper and lower surfaces of the alu~inum strip or wire to be electrolytically coloured.
In carrying out the process of this invention, the anodically oxidized aluminum strip or wire 1 is first thoroughly rinsed with water and then introduced by means o-f driving rollers, guide rollers or the like into the electrolytic colouring cell 2 where the aluminum strip or wire is brought into.contact with the colouring~bath 3. The aluminum strip or wire 1 further travels in the colouring bath and approaches the hollow bodies 7 where the aluminum strip or wire is to be electrolytically coloured. The colouring rate of the aluminum strip or wire increases as the aluminum strip or wire approaches the hollow bodies and decreases as the strip.or wire travels away from the hollow bodies. A
strip or wire which is completaly coloured finally emerges from the colouring bath.
Of course, during the above colouring procedure)direct~
current is passed through the colouring bath between the aluminum strip or wire as a cathode and the anode provided in the hollow body or bodies 7.
As described above, the characteristic feature of the present invention resides in that colouring occurs at areas where the aluminum strip or wire to be electrolytically coloured appro-aches close to the hollow bodies 7.
The hollow body 7 used in the present invention as the the electrolytic colouring means includes any type of hollow member which can be provided with an anode therein electrically insulated from other portions of the hollow body, and which has at least one inlet for introducing a colouring bath and an opening for supplying a colouring bath by flowing the same toward a travelling aluminum strip or wire disposed adjacent the bath supply opening. The hollow body can be of any shape, for example, 1~6~33~3 1 cylindrical or box-like. The opening in the hollow body is preferably a slit shape, the longitudina:l direction of the slit being perpendicular to the travelling direction of the aluminum strip or wire, but it may be of any shape so long as the opening is capable of flowing the colouring bath uniformly toward the travelling aluminum strip or wire.
The anode is also preferably arranged perpendicular to the travelling direction of the aluminum strip or wire,and is advantageously made from a material which is convenient for the maintenance of the colouring bath used, for example, a nickel plate when the colouring bath contains nickel ions. The amount of the colouring bath flowing or ejected through the opening can be controlled by liquid flow control means such as a valve, after pump 6.
The flow rate of the colouring bath and the slit width of the opening are not critical, and vary depending upon various parameters used in the process, but in large s/ le industrial apparatus it is preferred to use higher in-~ee~
rates and larger slit widths as the travelling rate of the aluminum strip or wire increases.
In another embodiment of the process of this invention, it is possible to electrolytically colour only one surface of an aluminum strip by, for example, using an apparatus as illustrated in Figure 2.
Referring now to Figure 2, members 1 to 10 have the same meanings as explained with reference to Figure 1, an~ the shape and the function of these members is the same as in Figure l; there are, however, two significant differences between the systems shown in Figures 1 and 2.
Firstly, aluminum strip 1 is not contacted with ~L~6~8 1 colouring bath 3 contained in colouring cell 2, but is contacted only with a colouring bath layer 12 formed on the surface of the travelling aluminum strip. When direct current is applied in this state between anode 8 and aluminum strip 1 while travelling the aluminum strip, an aluminum strip electrolytically coloured on only one surface (the surface which is contacted with the colouring bath layer 12) is obtained. Secondly, in this embodi-ment the colouring time can be adjusted by changing the distance between colouring-adjustment rollers 11 and 11', i.e., the longer the distance between the rollers, the longer the colouring time at constant rates of travel. Rollers 11 and 11' function only to adjust the length of the colouring bath layer 12, and can be made from a wide variety of materials, such as rubber, sponge, plastic and the l`ike. Rollers 11 and 11' may be eliminated i the rollers 4 are shifted to a position closer to each other so as to function as rollers 11 and 11'.
The characteristic feature of the embodiment of Figure 2 is that electrolytic colouring occurs only at the area i near the hollow body 7 a~d the colouring bath layer 12. Thus, a hollow body can be provided facing the lower surface of the aluminum strip to thereby electrolytically colour the lower surface of the aluminum strip, or the hollow body can be pro-vided facing both the upper and lower surfaces of the aluminum strip, thereby electrolytically colouring both surfaces o~
the aluminum strip. Further, it is possible to electrolytically colour the aluminum strip in special patterns, for example, in a stripe-pattern, by providing a particular type of hollow body.
For example, a stripe-pattern colouring in which deeply-coloured portions and lightly-coloured portions are parallel to the 106~38 travelling direction of the aluminum strip can be attained when the opening of one or more hollow bodies i5 partiall~ covered with an appropriate member, such as a rubber plate or sponye, and electrolytic colouring is conducted while setting the partiall~
covered hollow body or bodies close to the surface of the travelling aluminum stripO
In Figure 2, the hollow body 7 is provided at the upper surface of the aluminum strip, but as previously described, two or more hollow bodies can be provided at the upper and/or lower surface of the aluminum strip.
In the embodiment illustrated in Figure 2, the colouring bath sometimes tends to flow down to the edge portions of the lower surface of the aluminum strip, thereby partially colouring the edge portions. Such undesirable colouring can be prevented by increasing the flow rate of the colouring bath or by blowing pressurized air toward the lower surface of the al~inum strip.
~ he aluminum thus coloured is then washed with water and can then be subjected to a conventional sealing treatment `20 ~ various lacquer coating methods including electrodeposition, dipping and spraying, as are known in the art.
As will be apparent to one skilled in the art, when the electric polarity is reversed and an aqueous solution of sulfuric acid is used in place of the colouring bath in the embodiment shown in Figure 2, only one surface of the aluminum strip can be anodically oxidized; such as embodiment is not contemplated in the present invention.
As previously described, in accordance with the process of this invention, a stable, uniformly coloured aluminum strip or wire can be obtained without partial spalling of the 1~6l~8;3~3 ~
1 coloured film. Also, since the process of this invention makes it possible to electrolytically colour only one surface of an aluminum strip and, if desired, to colour an aluminum strip in a stripe-pattern, various coloured aluminum strips suitable for use in a wide variety of utilities can be obtained.
In addition, as a most significant feature of the process of this invention, anodically oxidized aluminum having a very thin anodic oxide film thereon, for example, an anodic oxide film having a thickness of 1 to 2 ~,which could not be effectively electrolytically coloured by conventional electrolytic colouring processes, can be coloured stably and uniformly by the process of this invention. The above fact indicates that electrolytically coloured strips and wires having an excellent resistance to weathering can be produced at low cost and, therefore, the effects brought about by the present invention are vexy important economically.
The present invention will be illustrated in further detail by reference to the following Examples~ but is not restricted thereto as the examples were conducted on a small ~ scale for purposes of illustration.
A coiled aluminum strip 65 mm (width) x 0.3 mm ~thick-ness) having an aluminum content of 99.2~ was mounted on the uncoiling means of an apparatus comprising an uncoiler, etching cel~, washing cell, current supplying cell, anodic oxidation cell, washing cell, electrolytic colouring cell, washing cell, seal-ing cell and a recoiler, and passed through the recited units in the order given. The apparatus used was substantially identical to that disclosed in Canadian Patent No. 1,032,106 filed March 6, 1974, except, of course, for the novel colouring .
~J . .
,., ~.
-` ~06083~
1 means of the present invention.
In the electrolytic colouring cell, the aluminum strip was immersed in a colouring bath and two hollow bodies were positioned ~acing both sur~aces of the aluminum strip, as shown in Figure 1. Each of the hol:Low bodies was in the form o~
a circular cylinder havlng a diameter of 30 mm and a length oE
lO0 mm. The hollow body was provided with a slit extending axially throughout the length thereof, the width of the slit beiny 1 mmO An anode plate of nickel was housed along the 1~ axis thereof, the dimensions of the anode plate being 20 ~m x 80 mm x 0.5 mm. The hollow bodies were disposed perpendicularly to the travelling direction of the strip, the distance between the strip and each hollow body being 1 m~. The aluminum strip was treated as described hereinafter.
The aluminum strip was introduced into the etching cell through the uncoiler at a rate of 20 cm/min, and contacted therein with a 10% aqueous sodium hydroxide solution at a bath temperature of 50C for one minute, and passed therethrough to the washing cell where the aluminum strip was passed through a water bath-The resulting strip was then introduced into the current supplying cell which contained a 30% aqueous sulfuric acid solution in which was disposed a carbon anode plate, wherein the aluminum strip was subjected to electrolysis at a current density o~ 2.0 A/dm2 at a bath temperature of 25 C for
4.5 minutes (electrolysis time), the aluminum strip acting as a cathode.
The aluminum strip was then introduced into the anodic oxidation cell which contained a 30% aqueous sulfuric acid solution in which was disposed a carbon cathode plate, wherein 3 C3 6(~1~31 3 1 the aluminum strip was subjected to anodic oxidation at a current density of 2.0 A/dm~ and a bath temperature of 25C for
The aluminum strip was then introduced into the anodic oxidation cell which contained a 30% aqueous sulfuric acid solution in which was disposed a carbon cathode plate, wherein 3 C3 6(~1~31 3 1 the aluminum strip was subjected to anodic oxidation at a current density of 2.0 A/dm~ and a bath temperature of 25C for
5 minutes (electrolysis time) to thereb~ form an oxide film of a thickness of about 3 microns on the aluminum strip.
After subsequently passing through a washing cell as above, the aluminum strip was introduced into the electrolytic colouring cell in which the hollow bodies were disposed, as earlier described, and subjected to cathodic electrolysis. The electrolytic bath in the electrolytic colouring cell comprised an aqueous solution of 50 g/liter o~ nickel sul~ate and 30 g/
liter o~ boric acid. While injecting this electrolytic bath at a rate of 8 liter/min per l cm2 of the opening area of the hollow body, the aluminum strip was subjected to cathodic electrolysis at a current density of 1.0 A/dm2 and at a bath temperature of 25C for a colouring time o~ 20 seconds (electrolysis time). As a result, both surfaces of the aluminum strip were uniformly coloured bronze without undesirable defects such as stripe-pattern or film-breakage~
The aluminum strip thus coloured was then passed through a washing cell as above described, then introduced into the sealing cell in which the aluminum strip was sealed with pure water at 93C for 8 minutes (the colour tone of the aluminum strip thus treated did not chang-e) and coiled.
The coloured aluminum strip thus obtained had excellent processability, and cracks in the oxide film on the aluminum strip were hardly encountered even when the aluminum strip was subjected to press processing or roll processing.
An aluminum strip was coloured on one sur~ace usin~
the same apparatus as employed in Example l except that a hollow 83~
1 body was provided at only one surface of the aluminum strip as shown in Figure 2.
The aluminum strip was treated under the same con-ditions as employed in Example 1 to -the anodic oxidation cell.
After passing through the anodic oxldation cell, the aluminum strip was further passed through the washing cell and then introduced into the electrolytic co:Louring ~ell containing therein the same electrolytic bath as was employed in Example 1.
In this step, while injecting the electrolytic bath at a rate of 10 liter/min. per 1 cm2 of the opening area of the hollow body, the aluminum strip was subjected to cathodic electrolysis at a current density of 1.0 A/dm2 and at a bath temperature of 25C for a colouring period of 10 seconds (electrolysis time). After completion of this treatment, the aluminum strip was successively passed through the washing cell and the sealing cell under the same conditions as employed in Example 1 and then coiled.
As a result only the surface of the aluminum strip facing the hollow body was uniformly coloured bronze. The ~ aluminum strip thus obtained was found to have excellent processability the same as that obtained in Example 1.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one s~illed in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
3~ - 15 -
After subsequently passing through a washing cell as above, the aluminum strip was introduced into the electrolytic colouring cell in which the hollow bodies were disposed, as earlier described, and subjected to cathodic electrolysis. The electrolytic bath in the electrolytic colouring cell comprised an aqueous solution of 50 g/liter o~ nickel sul~ate and 30 g/
liter o~ boric acid. While injecting this electrolytic bath at a rate of 8 liter/min per l cm2 of the opening area of the hollow body, the aluminum strip was subjected to cathodic electrolysis at a current density of 1.0 A/dm2 and at a bath temperature of 25C for a colouring time o~ 20 seconds (electrolysis time). As a result, both surfaces of the aluminum strip were uniformly coloured bronze without undesirable defects such as stripe-pattern or film-breakage~
The aluminum strip thus coloured was then passed through a washing cell as above described, then introduced into the sealing cell in which the aluminum strip was sealed with pure water at 93C for 8 minutes (the colour tone of the aluminum strip thus treated did not chang-e) and coiled.
The coloured aluminum strip thus obtained had excellent processability, and cracks in the oxide film on the aluminum strip were hardly encountered even when the aluminum strip was subjected to press processing or roll processing.
An aluminum strip was coloured on one sur~ace usin~
the same apparatus as employed in Example l except that a hollow 83~
1 body was provided at only one surface of the aluminum strip as shown in Figure 2.
The aluminum strip was treated under the same con-ditions as employed in Example 1 to -the anodic oxidation cell.
After passing through the anodic oxldation cell, the aluminum strip was further passed through the washing cell and then introduced into the electrolytic co:Louring ~ell containing therein the same electrolytic bath as was employed in Example 1.
In this step, while injecting the electrolytic bath at a rate of 10 liter/min. per 1 cm2 of the opening area of the hollow body, the aluminum strip was subjected to cathodic electrolysis at a current density of 1.0 A/dm2 and at a bath temperature of 25C for a colouring period of 10 seconds (electrolysis time). After completion of this treatment, the aluminum strip was successively passed through the washing cell and the sealing cell under the same conditions as employed in Example 1 and then coiled.
As a result only the surface of the aluminum strip facing the hollow body was uniformly coloured bronze. The ~ aluminum strip thus obtained was found to have excellent processability the same as that obtained in Example 1.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one s~illed in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
3~ - 15 -
Claims (8)
1. In a process for electrolytically colouring an anodically oxidized aluminum or aluminum base alloy strip or wire as a cathode in a colouring bath comprising an aqueous solution containing at least one nickel salt, cobalt salt, tin salt, iron salt, copper salt or selenious acid while continuously travelling said anodically oxidized aluminum or aluminum base alloy strip or wire, the improvement which comprises subjecting said anodically oxidized aluminum or aluminum base alloy strip or wire as a cathode to direct current electrolysis using an electrolytic colouring means comprising at least one hollow body having an anode therein and an opening for continuously supplying the colouring bath onto at least one surface of said strip or wire, while continuously supplying said colouring bath onto at least one surface of said aluminum or aluminum base alloy strip or wire.
2. The process according to claim 1, wherein said hollow body is provided at one surface of the anodically oxidized aluminum or aluminum base alloy strip or wire.
3. The process according to claim 1, wherein said colouring bath is in the form of a layer on the surface of the anodically oxidized aluminum or aluminum base alloy strip or wire.
4. The process according to claim 1, wherein said direct current electrolysis in said colouring bath is conducted for a period of about 30 seconds or less.
5. The process according to claim 4, wherein said direct current electrolysis in said colouring bath is conducted for a period of 2 to 15 seconds.
6. The process according to claim 1, wherein the distance between the lower portion of said opening provided in said hollow body and the surface of said strip or wire facing said opening is controlled to be less than about 100mm.
7. The process according to claim 1, wherein said open-ing of the hollow body is a slit shape and the longitudinal dir-ection of the slit is perpendicular to the travelling direction of said strip or wire.
8. The process according to claim 1, wherein said anode in the hollow body is arranged perpendicular to the travelling direction of said strip or wire.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13343474A JPS5159040A (en) | 1974-11-19 | 1974-11-19 | Aruminiumuobiita oyobi sennorenzokudenkaichakushokuhoho |
| JP13343374A JPS5159039A (en) | 1974-11-19 | 1974-11-19 | Aruminiumuobiita oyobi senno renzokudenkaichakushokuho |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1060838A true CA1060838A (en) | 1979-08-21 |
Family
ID=26467797
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA239,988A Expired CA1060838A (en) | 1974-11-19 | 1975-11-18 | Process for continuous electrolytic coloring of aluminum or aluminum base alloy strip and wire |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1060838A (en) |
| DE (1) | DE2551947C3 (en) |
| FR (1) | FR2292058A1 (en) |
| GB (1) | GB1518979A (en) |
| NO (1) | NO143671C (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58107498A (en) * | 1981-12-18 | 1983-06-27 | Fuji Photo Film Co Ltd | Method and apparatus for electrolytic treatment of strip like metal plate |
| DE102015009944B4 (en) * | 2015-06-29 | 2019-03-14 | Diehl Metal Applications Gmbh | Connector made of a band of an aluminum alloy |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1434701A (en) * | 1974-02-20 | 1976-05-05 | Alcan Res & Dev | Process and apparatus for electrolytic colouration of anodised aluminium |
-
1975
- 1975-11-14 GB GB47003/75A patent/GB1518979A/en not_active Expired
- 1975-11-18 CA CA239,988A patent/CA1060838A/en not_active Expired
- 1975-11-18 NO NO753877A patent/NO143671C/en unknown
- 1975-11-19 DE DE2551947A patent/DE2551947C3/en not_active Expired
- 1975-11-19 FR FR7535345A patent/FR2292058A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| NO753877L (en) | 1976-05-20 |
| NO143671C (en) | 1981-03-25 |
| NO143671B (en) | 1980-12-15 |
| FR2292058B1 (en) | 1978-07-28 |
| GB1518979A (en) | 1978-07-26 |
| DE2551947C3 (en) | 1979-06-28 |
| DE2551947A1 (en) | 1976-05-20 |
| DE2551947B2 (en) | 1978-10-05 |
| FR2292058A1 (en) | 1976-06-18 |
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