Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Forming nonmetal coating
Reexamination Certificate
2000-03-28
2001-11-27
Dawson, Robert (Department: 1712)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Forming nonmetal coating
C205S316000, C205S323000, C204S222000, C204S273000
Reexamination Certificate
active
06322689
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an anodizing method of a metal body using vibrationally, fluidly stirring and an apparatus for performing the same.
2. Description of the Related Art
In the field of manufacturing metal articles such as those made of aluminum, aluminum alloy, magnesium, magnesium alloy, etc. having an anodic oxide film on the surface of a metal body by using the anodizing process, it has been required to reduce the energy consumption and to improve the productivity and, in particular, to realize speeding up of the anodizing process, improvement in efficiency of oxide film forming. Furthermore, it has been required to realize the speeding up of the anodizing process under the condition that the higher temperature or room temperature treatment bath is used.
In fact, the most significant problem in the conventional anodizing process is that very long period of process time is necessary even if thinner oxide film having the thickness of 10 to 15 &mgr;m is formed. Therefore, in the manufacturing line for the metal article, for example a sash window, made of anodized aluminum, the anodizing process must be performed with use of a plurality of treatment apparatuses arranged in parallel to each other in order to avoid stagnation of the line, because the anodizing process takes about 10 to 15 times of the duration of time as compared with the pre-treatment process and post-treatment process.
The inventor has proposed an anodizing process in which micro bubbles having a diameter of 50 to 80 &mgr;m are continuously supplied to the treatment surface of alumimum body so that the anodizing rate is increased to the extent of 2 to 3 times of that of the conventional anodizing process. However, this process is still insufficient in the treatment rate and the treatment temperature.
On the other hand, in Japanese Patent Application Publication No. Sho-60-9600, there is disclosed an anodizing method in which numerous bubbles having a diameter of 0.001 to 4 mm are generated by the aeration apparatus in the electrolytic bath, and the bubbles are subjected to vibration of frequency of 10 to 200 Hz and allowed to move upwardly so that the efficiency of the anodizing process is improved. However, this technique is still insufficient, because oxygen generated by the electrolysis around the anode tends to form bubbles which is transferred to the atomosphere, and therefore the oxidative function thereof on the metal body becomes lowered. In addition, oxygen bubble formation results in increase of electrical resistance of the surface of the metal body and the higher voltage is required for the treatment so that the greater electric power is necessary and thus the heat release and energy loss become greater. Accordingly, it is considered that this conventional technique is practically used with the lower current density, for example 2 to 3 A/dm
2
, and therefore cannot realize the speeding up of the anodizing process under the condition that the higher temperature or room temperature treatment bath is used.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an anodizing method with higher anodizing rate, less energy consumption and higher efficiency of oxide film formation.
Another object of the present invention is to provide an anodizing method in which an excellent, uniform oxide film can be obtained without burning of the metal body even if the metal body has a complicated profile.
According to a first aspect of the present invention, in order to attain the above object, there is provided an anodizing method of a metal body, comprising an anodizing treatment process in which an anodic oxide film is formed on a surface of the metal body immersed in a treatment bath, the anodizing treatment process being performed while the following steps (a) and (b) are simultaneously carried out:
(a) a step of vibrationally fluidly stirring the treatment bath, wherein the treatment bath is vibrationally fluidly stirred by vibrating a vibration vane at an amplitude from 0.5 to 3.0 mm and at a vibrational frequency of 200 to 800 times per minute; and
(b) a step of performing an aeration in the treatment bath by using air bubbles generated by a diffuser having a pore opening of 10 to 400 &mgr;m.
In the anodizing method, the anodizing treatment process may be performed while at least one of the following steps (c) and (d) are simultaneously carried out:
(c) a step of applying vibration to the metal body, wherein the metal body is vibrated at an amplitude from 0.5 to 1.0 mm and at a frequency of 100 to 300 times per minute; and
(d) a step of swinging the metal body, wherein the metal body is swung at a swing amplitude from 10 to 100 mm and at a swing frequency of 10 to 30 times per minute.
According to a second aspect of the present invention, there is provided an anodizing method, comprising an anodizing treatment process in which an anodic oxide film is formed on a surface of a metal body immersed in a treatment bath, the anodizing treatment process being performed while the following apparatuses (A) and (B) are simultaneously operated:
(A) a vibrationally fluidly stirring apparatus for the treatment bath, which comprises a vibration generating means containing a vibration motor, a vibrationally fluidly stirring means for vibrating a vibration vane at an amplitude of 0.5 to 3.0 mm and at a vibrational frequency of 200 to 800 times per minute to generate vibrational flow in the treatment bath, the vibration vane being fixed in one stage or in multistage to a vibrating bar which vibrates in the treatment bath interlockingly with the vibration generating means, and a vibration stress dispersing means at a connection portion of the vibration generating means and the vibrationally fluidly stirring means; and
(B) an aeration apparatus for the treatment bath, which comprises a ceramic diffusing pipe having a pore-size of 10 to 400 &mgr;m.
The apparatus (A) further comprises an inverter for controlling the vibration motor of the apparatus (A) to generate any frequency in the range from 10 to 500 Hz. The power of the vibration motor is set to an appropriate value according to volume of the treatment bath.
The ceramic diffusing pipe of the apparatus (B) may have a porosity of 30 to 40%. For example, in case of a diffusing pipe which is obtained by forming many holes each having a pore size of about 1 mm in a pipe of synthetic resin such as PVC, electrolytic heat cannot be effectively removed because air bubble size is excessively large, and there occurs a dispersion in electrical resistance of the system. On the other hand, the aeration apparatus (B) according to the present invention uses a ceramic porous pipe as a diffusing pipe, and thus the above problem can be avoided, that is, Joule heat generated in the system can be removed. A high-temperature sintered ceramic pipe which contains alumina grain such as ALUNDUM (trade name) as bone material is preferably used as the ceramic porous pipe. The pore-size of the diffusing pipe is suitably set to 10 to 400 &mgr;m, preferably 10 to 120 &mgr;m, and the porosity (the ratio of the area of pores to the surface area) is preferably set to about 30 to 40%. The outer diameter of the diffusing pipe is typically set to 50 to 100 mm, and the length thereof is typically set to about 1000 to 1500 mm although it is varied in accordance with the length of the treatment tank. A method of disposing the diffusing pipe is not limited to a specific one, however, if plural diffusing pipes are used, they are disposed so that the air bubbles generated by the aeration come around the metal body uniformly. The interval between the diffusing pipes is preferably set to 100 to 120 mm, and the interval in the vertical direction between the diffusing pipe and the metal body is preferably set to 100 to 300 mm. According to such an arrangement, the aeration can be strengthened as twice degree as compared with the conventional aeration.
In the anodizing method, the anodizing treatment process may be performed while at lea
Dawson Robert
Feely Michael J
Japan Techno Co. Ltd.
Pitney Hardin Kipp & Szuch LLP
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