JPH1096099A - Electrodeposition coating method for aluminum surface treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain uniform coating films good in throwing power of electrolytic coloring even if simultaneous electrodeposition coating is executed by supplying two energizing frames for one electrolytic bath in a method for electrodeposition coating of aluminum works framed by the energizing frames. SOLUTION: DC power sources or current rectifiers 5A, 5B and internal switches 6A, 6B are connected respectively to the two energizing frames 4A, 4B. Controllers 7A, 7B which turn off the internal switches by detecting the prescribed quantity of currents are connected to these current rectifiers 5A, 5B and the internal switches 6A, 6B. The Coulomb quantity (current × time) meeting the surface areas of the works 3A, 3B of the respective energizing frames 4A, 4B is previously set and a simultaneous electrolysis is executed by immersing the two energizing frames 4A, 4B into the same electrolytic bath a. The internal switches 6A, 6B are turned off by the controllers 7A, 7b which detect the set Coulomb quantity described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition coating of aluminum or an aluminum alloy, and more particularly, to a uniform electrodeposition coating method with good throwing power.

[0002]

2. Description of the Related Art Electrodeposition coating of an aluminum profile or the like is performed by integrating a plurality of workpieces made of a profile or the like by forming a frame with a conductive transfer frame and supplying the transfer frame to a battery case as a current supply frame. Then, immersed in an electrolytic bath in a battery case, i.e., a bath containing an anionic or cationic electrodeposition coating solution made of a conductive aqueous resin or the like, and the object to be coated attached to the current-carrying frame is treated as an anode or a cathode. As a direct current voltage is applied between the counter electrode in the battery case and the coating component is migrated, and the coating is deposited on the object to be coated.The deposited coating is gradually dehydrated and it becomes difficult for the current to pass. There is a feature that the surface moves and a coating film having a relatively uniform film thickness can be formed as a whole as compared with other coating methods.

As shown in FIG. 2A, such an electrodeposition coating method generally includes a rectifier connected to an AC power supply for each of electrolytic baths b and c in a two-bath type electric tank 10. Energizing frame 13A including 11A and internal switch 12A
And a current-carrying frame 13B provided with the same rectifier 11B and internal switch 12B is supplied between the pair of battery-tank-electrodes 14A and 14B provided for each of the electrolytic baths b and c by a one-bath-one-frame method. A voltage is applied between the electrode 13B and the counter electrodes 14A, 14B to perform electrodeposition coating of the objects 15A, 15B.

In consideration of workability and work scale, FIG.
As shown in (b), two electrolytic baths 19A and 19B are simultaneously supplied to an electrolytic bath d in one electric container 16 so as to share a set of a rectifier 17 and an internal switch 18. According to the method, a voltage is applied between the pair of counter electrode plates 20 provided on both sides of the battery case 16 to apply two frames of the objects to be coated 21A and 21B.
May be simultaneously electrodeposited.

[0005]

However, the former one for supplying a current-carrying frame provided with a rectifier for each electrolytic bath one by one.
In the case of the bath 1 frame method, the flow of current to the workpiece is uniform,
Although the coverage of the coating film is good, the number of electrode plates in the battery case is large for the object to be coated, and a two-bath type battery case in which electrolytic baths are arranged in parallel is necessary in terms of work efficiency. There is a problem that the initial cost, mainly the equipment cost, becomes high, such as an increase in the width of the tank and an increase in the installation area of the battery case.

In the latter one-bath, two-frame system, in which two current-carrying frames are simultaneously supplied to one electrolytic bath, the non-opposite surface of the object facing the opposite sides of the two current-carrying frames is displaced around the current. Therefore, there is a problem that the film thickness of the electrodeposition coating film is apt to be reduced, and when performing electrodeposition coating of two frames simultaneously in this one electrolytic bath, the supply current is controlled without discriminating between both current frames. Since it is carried out for the amount, especially in the simultaneous processing of the energizing frame with the workpieces with different processing areas attached,
For example, the film thickness of the workpiece with a small processing area becomes excessively thick.
There has been a problem that the throwing power of the paint becomes worse as compared with the former one-bath one-frame system in which a counter electrode plate is disposed on both sides of one energizing frame to perform electrodeposition coating.

The present invention has been made in view of the above-mentioned problems, and in the electrodeposition coating of aluminum surface treatment, even if two electrode frames are supplied simultaneously for one electrolytic bath to perform simultaneous electrodeposition coating, the present invention is not limited thereto. It is an object of the present invention to provide an electrodeposition coating method which can provide a coating film having good throwing power and can cope with restrictions on a building and equipment area.

[0008]

In order to achieve the above-mentioned object, the present invention provides an electrodeposition coating method for electrodepositing an aluminum object to be framed with an energizing frame. A DC power supply and an internal switch are connected to each other, and a controller for detecting a set coulomb amount and turning off the internal switch is connected to the DC power supply and the internal switch. A coulomb amount was set in accordance with the processing area, and the two current-carrying frames were simultaneously immersed in the same electrolytic bath to apply a voltage, and the internal switch was turned off by detecting the set coulomb amount. It is another object of the present invention to provide an electrodeposition coating method in aluminum surface treatment.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG.
A predetermined electrodeposition coating liquid a is accommodated, and a pair of cathodes 2 or anodes are arranged on both sides.
A, 3B, two energizing frames 4A, 4 integrated with each other
B, rectifiers 5A and 5B connected to an AC power supply (not shown) as DC power supplies and internal switches 6A and 6B are connected to the rectifiers 5A and 5B and the switches 6A and 6B.
Are connected to controllers 7A and 7B, respectively.
A predetermined amount of current, that is, a predetermined amount of coulomb (current × time) corresponding to the processing area of the workpieces 3A and 3B attached is input to 7B, and the switch is turned off when the amount of coulomb is reached. Set to.

When the two current supply frames 4A and 4B are supplied as anodes or cathodes to the battery case 1 and a predetermined voltage is applied, the coating material of the electrodeposition coating liquid a migrates and each of the current supply frames 4A and 4B, the objects 3A and 3
In B, the coating material corresponding to the amount of electricity is coagulated and deposited, and the coating is performed. When the energization amount reaches a predetermined coulomb value, the switches 6A and 6B are turned off through the respective controllers 7A and 7B, and the electrodeposition coating ends. Therefore, even for an energization frame with a small processing area, no excessive current flows,
Electrodeposition similar to the case of the energizing frame having a large processing area is performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG.
The controller 7A connected to the controller 7 detects the amount of current flowing through the workpiece 3A of the energizing frame 4A, and performs a coulomb control to turn off the energization by the internal switch 6A when the amount of coulomb reaches a preset coulomb amount. In the second system, the controller 7B also performs the same control of detecting the set coulomb amount and turning off the internal switch 6B based on the amount of current flowing through the workpiece 3B of the energizing frame 4B.

As a conventional example 1, a conventional one-bath, one-frame method using a two-bath type battery case shown in FIG.
Electrodeposition coating is performed by the conventional one-bath, two-frame method in which electrodeposition coating is performed using the same power supply shown in FIG. 2B, and the coulomb amount is supplied by the individual power supply shown in FIG. Electrocoating was carried out by the one-bath, two-frame system of the method of the present invention in which control could be performed for each frame, and the throwing power of the paint was compared.

[0013] As the object to be coated, an aluminum alloy extruded shape members according to the provisions of the A6063-T ₅ in JIS H 4100, width 100 mm, vertical width 33 mm, surface area length 5.0m long of 1.7 m ² C Mold members were used. For each electrolytic bath component, a first current-carrying frame (surface area meter: 40.8 m ² ) having 24 C-shaped members attached thereto, and a ^second current-carrying frame (surface area meter) also having 24 C-shaped members attached thereto. 40.8 m ² ) was prepared, immersed as an anode in an electrolytic bath in a battery case of each type containing a cationic electrodeposition coating solution, and electrolyzed at a set voltage of 150 V as in the past. In the method of the present invention, the set coulomb was set to 650 coulomb / m ^2, and the voltage was set to 150 V after a soft start by a low voltage for 30 seconds.

The thickness of the coating film was measured for each of the thus-obtained treated coatings at six positions, that is, the counter electrode surface and the non-counter electrode surface at the upper 50 cm, the center, and the lower 50 cm. Average thickness X of the obtained coating films in Conventional Examples 1 and 2 and Example 1
Table 1 shows _mean and its variation σ.

[0015]

[Table 1]

According to the results, according to the method of the present invention, the conventional one bath 2
It can be seen that a coating film having a better throwing power and less variation than in the case of the frame method is obtained, and a coating film having a good throwing power comparable to the conventional one-bath one-frame method is obtained.

Further, as in the case of the first embodiment, the processing area of the object to be coated of the current-carrying frame is changed. Electrodeposition coating was performed using a bath 2 frame 1 power supply system, and as Example 2, electrodeposition coating was performed using the same electrolytic bath 2 frame 2 power supply system of the present invention, and the results were compared. The object to be processed is a C-type aluminum alloy extruded material having the same dimensions as in the first embodiment. Twelve objects are attached to the first frame as the current-carrying frame, the processing surface area is 20.4 m ^2, and the second 2 in the frame
Four of them were attached to make the processing surface area 40.8 m ² . Other processing conditions and measurement conditions of the coating film thickness were the same as those in Comparative Examples 1 and 2 and Example 1. The average thickness X _mean of the obtained coating film and its variation σ are shown in Table 2 as Comparative Examples 3 and 4 and Example 2.

[0018]

[Table 2]

According to the method of the present invention, even when the processing areas of the objects to be processed in the energizing frame are different, the two electrolytic baths of the same type can be sufficiently used as compared with the conventional one-bath, two-frame, one-power system. A coating film having excellent throwing power was obtained, and a coating film having a uniform thickness and a good rotation was obtained, which was almost equivalent to the conventional one-bath one-frame system.

[0020]

As described above, according to the method of the present invention,
Although the same electrolytic bath two-frame system is used, similar good results can be obtained as in the conventional one-bath one-frame system. Therefore, the width of the conventional two-bath type battery case can be shortened, and therefore, the building and site can be shortened. There is an effect that the initial cost can be greatly reduced, such as a reduction in the number of return electrode plates without any concern, and a reduction in equipment costs.

[Brief description of the drawings]

FIG. 1 is a schematic front sectional view showing a battery case for carrying out the method of the present invention.

FIG. 2 is a schematic front sectional view showing a battery case for carrying out a conventional method, wherein (a) shows a case of the same electrolytic bath one-frame method and (b) shows a case of the same electrolytic bath two-frame method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Counter electrode 3A, 3B Workpiece 4A, 4B Energizing frame 5A, 5B Rectifier 6A, 6B Internal switch 7A, 7B Controller a Electrolytic bath

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuhiko Sawai 13-13 Nagonoe, Shinminato City, Toyama Prefecture Inside Toyama Light Metal Industry Co., Ltd. (72) Inventor Hironobu Kato 13-13 Nagonoe, Shinminato City, Toyama Prefecture 3 Toyama Light Metal Industry Inside the corporation

Claims (1)

[Claims] In an electrodeposition coating method for electrodepositing an aluminum object framed by an energizing frame, a DC power supply and an internal switch are connected to each of the two energizing frames and a set coulomb amount is detected. A controller for turning off the internal switch is connected to the DC power supply and the internal switch, and a coulomb amount is set in accordance with the processing area of the object to be coated framed in each of the current supply frames. An electrodeposition coating method in aluminum surface treatment, wherein a frame is simultaneously immersed in the same electrolytic bath to apply a voltage, and the internal switch is turned off by detecting the set coulomb amount.