JP2014028988A - Electrode, electrolytic device and electrodeposition coating method using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode and an electrolytic device that enable an electrolyte and an electrodeposition coating to be efficiently cooled for stabilization of a bath temperature, and an electrodeposition coating method using them.SOLUTION: An electrode includes cooling means inside it. An electrolytic device includes a counter electrode comprising the electrode, and a working electrode. The cooling means uses water as a cooling medium, and preferably has a passage for water conduction from the lower side to the upper side.

Description

  The present invention relates to an electrode for efficiently cooling a bath and stabilizing the bath temperature, an electrolysis apparatus, and an electrodeposition coating method using them.

  Electrolysis (including electrodeposition) is used in a wide range of fields for the purpose of improving functionality and aesthetics or preventing rust. For example, electrolysis (anodization) performed with aluminum or an aluminum alloy material is used in the field of capacitors for the purpose of improving corrosion resistance and wear resistance, or coloring. Electroplating and electrodeposition coating are used in the fields of home appliances, architecture and automobiles for the purpose of corrosion resistance and imparting aesthetics, and have a wide range of application examples.

  The electrolytic solution in the above electrolysis, the plating solution, and the electrodeposition coating in the electrodeposition coating (hereinafter sometimes collectively referred to as a bath) obtain a specified film thickness, impart appropriate functionality to the sample, and ensure safety. From the standpoint of maintaining the temperature, the operating temperature range is often set for each electrolyte, plating solution, and electrodeposition paint, and the temperature of the electrolyte, plating solution, and electrodeposition paint (hereinafter referred to as bath temperature). Control is also very important. When electrolysis or electrodeposition coating is actually performed, current flows between the electrode to be electrolyzed or the electrodeposition coating sample (working electrode) and the counter electrode to generate Joule heat, increasing the bath temperature. Therefore, it is necessary to cool the bath temperature. For example, there is a method of cooling the bath temperature by incorporating a cooling function in the apparatus, but it is difficult to keep the bath temperature constant.

  In order to solve the above problem, for example, in Patent Document 1, in an electrodeposition coating apparatus, when the temperature of the electrodeposition liquid rises or falls, the electrodeposition liquid is circulated, cooled or heated, and electrodeposition is performed. A method for controlling the temperature of the liquid has been proposed. At this time, when the temperature of the electrodeposition liquid is high, cooling is performed by a cooling heat exchanger via a cooling control valve, and when the temperature of the electrodeposition liquid is low, heating is performed via a heating control valve. The temperature of the electrodeposition liquid can be controlled by heating with a heat exchanger.

  Further, in Patent Document 2, in the electrolytic processing apparatus, the cooling liquid is allowed to flow on the outer periphery of the electrolytic cell, and further, the heat radiation fins are projected from the outer peripheral wall of the electrolytic cell. It is possible to do.

JP 2005-256096 A JP-A-5-239700

  However, in the technique proposed in Patent Document 1, a new tank is required to cool or heat the electrodeposition liquid, and the opening / closing control of the valve is required, which makes the apparatus large. In addition, since the reaction occurs in the electrodeposition tank even when the electrodeposition liquid is circulated, when the electrodeposition liquid after circulation and the electrodeposition liquid in the electrodeposition tank are mixed, There is a possibility that it may be different from the concentration of the electrodeposition solution, and there is a problem that a uniform film thickness cannot be obtained.

  Although it is conceivable that the cooling function can be improved by expanding the contact area as in the technique proposed in Patent Document 2, since the cooling is performed through the electrolytic cell, a significant improvement in the cooling capacity cannot be expected.

  The present invention has been made in view of such circumstances, and provides an electrode, an electrolysis apparatus, and an electrodeposition coating method using the same for enabling the bath to be efficiently cooled and stabilizing the bath temperature. With the goal.

  Therefore, the present inventors paid attention to an electrode serving as a counter electrode disposed inside the electrolytic cell. As a result, it has been found that the bath temperature can be efficiently controlled by providing a cooling means inside the electrode and providing a cooling function.

The present invention has been completed as a result of intensive studies based on the above findings, and the gist thereof is as follows.
[1] An electrode having cooling means inside.
[2] The electrode according to [1], wherein the cooling means cools using water as a refrigerant.
[3] The electrode according to [2], wherein the cooling means has a path through which water flows from the lower part to the upper part.
[4] An electrolysis apparatus comprising a counter electrode composed of the electrode according to any one of [1] to [3] and a working electrode.
[5] The electrolysis apparatus according to [4], wherein a distance between the counter electrode and the working electrode can be changed.
[6] Using the electrolytic apparatus according to [4] or [5], the counter electrode is an anode, the working electrode is a cathode made of a metal material, and the electrodeposition paint is used as an electrolytic solution, and the electrodeposition is applied to the metal material An electrodeposition coating method characterized by

  According to the present invention, it is possible to efficiently and stably cool a bath that has risen due to Joule heat without causing a concentration distribution in the electrolytic cell. As a result, for example, it is possible to perform electrodeposition coating with a uniform film thickness on an electrolytic sample of a metal material such as a steel plate.

It is one of the one embodiment of the electrolysis device by the present invention, and is a section schematic diagram. It is one of the one Embodiment of the electrolysis apparatus by this invention, and is an upper surface schematic diagram. 1 is a schematic view of the inside of an electrode according to the present invention. It is the schematic of an example of the conventional electrolysis apparatus.

The present invention is described in detail below.
1 and 2 show an electrolysis apparatus according to an embodiment of the present invention. 1 is a schematic sectional view, and FIG. 2 is a schematic top view. According to FIGS. 1 and 2, a direct current that applies a voltage between an electrolytic cell 3 in which the electrolytic solution 1 is stored and a working electrode 2 that is an electrolyzed sample is immersed, and the working electrode 2 and its counter electrode 5 is applied. A power source 4 and a stirring means 6 such as a stirrer for stirring the electrolytic solution 1 are provided at the bottom of the electrolytic cell 3. The counter electrode (electrode) 5 is connected to the anode side of the DC power supply 4 and the working electrode 2 is connected to the cathode side, and a voltage is applied between both electrodes.

  Here, the counter electrode (electrode) 5 has means for cooling the electrolytic solution 1, and for example, a coolant for cooling is stored in the counter electrode (electrode) 5. For example, water can be used as the refrigerant. Thus, by using the counter electrode (electrode) 5 having a means for cooling the electrolytic solution 1 inside, the electrolytic solution 1 can be efficiently cooled and the bath temperature can be controlled. As a result, when the electrolysis apparatus is used for electrodeposition coating, it is possible to perform electrodeposition coating with a film thickness with little variation.

  Further, inside the counter electrode (electrode) 5, there is a path through which water flows from the lower part to the upper part as shown in FIG. 3, so that the direction of travel of the refrigerant is gradually increased so that bubbles that enter from the inlet side do not accumulate. Such a structure is preferable. According to FIG. 3, the refrigerant flows from the refrigerant inlet side 7, accumulates from the lower part, flows from the lower part to the upper part of the counter electrode 5, and flows out from the refrigerant outlet side 8. Thus, the refrigerant inside the counter electrode (electrode) 5 flows from the lower part to the upper part of the counter electrode (electrode) 5 so that the refrigerant is filled from the lower part, and bubbles in the refrigerant stay inside the counter electrode (electrode) 5. Thus, the refrigerant can flow stably at a constant flow rate, and the cooling efficiency is improved.

  The material of the counter electrode (electrode) 5 is not particularly limited, but it is desirable that the counter electrode (electrode) 5 itself has a small characteristic change even when a large current flows.

  As described above, the electrolysis apparatus of the present invention includes the counter electrode (electrode) 5 having the means for cooling the electrolyte solution 1 and the working electrode 2. A plurality of counter electrodes (electrodes) 5 are preferably arranged so as to face the surface of the working electrode 2 and be symmetrical about the working electrode 2. By disposing it directly on the surface of the working electrode 2, the distance between the electrodes becomes constant, and a stable film thickness can be obtained. In addition, by arranging a plurality of symmetrically, it is possible to obtain a constant film thickness on both surfaces of the working electrode 2, and a plurality of counter electrodes (electrodes) 5 are arranged to sandwich the electrolytic solution 1. And it can cool stably.

  Furthermore, the positions of the counter electrode (electrode) 5 and the working electrode 2 are variable so that the distance between the counter electrode (electrode) 5 and the working electrode 2 (hereinafter referred to as the interelectrode distance) can be changed. Is preferred. The distance between the electrodes is often determined by the specifications of the electrolytic solution 1, and the distance between the electrodes needs to be appropriately changed with respect to the thickness of the working electrode 2. Therefore, it is preferable that the position of the counter electrode (electrode) 5 and the working electrode 2 can be varied in the direction perpendicular to the surface of the counter electrode (electrode) 5 or the surface of the working electrode 2.

  As described above, according to the electrode and the electrolysis apparatus of the present invention, Joule heat is generated when a current flows from the DC power source 5 to the counter electrode (electrode) 5 and the working electrode 2, but the counter electrode (electrode) 5 is directly connected to the electrolyte solution 1. Because of the contact, heat exchange is easily performed, and bath temperature control is greatly facilitated compared to the conventional case. Furthermore, by using an electrode having a cooling path for passing water from the lower part to the upper part inside the counter electrode (electrode) 5, the cooling efficiency is improved, and a significant cooling effect can be obtained as compared with the conventional electrolyzer. .

  The electrolysis apparatus to which the electrode and electrolysis apparatus of the present invention are applied is not particularly limited, and covers all electrolysis apparatuses such as anodization, electroplating, and electrodeposition coating. In particular, it is particularly preferable to use the electrolysis apparatus of the present invention to perform electrodeposition coating on a metal material using the counter electrode as an anode, the working electrode as a cathode made of an electrodeposition coating sample, and the electrodeposition paint as an electrolyte. This is because electrodeposition coating greatly affects the bath temperature on the film thickness of the electrodeposition coating film, and the bath temperature control must be strict, and the electrolysis apparatus of the present invention facilitates bath temperature control. The electrodeposition coating sample is not particularly limited and is intended for metal materials in general, but is particularly suitable for steel plates that have many application examples of electrodeposition coating. Furthermore, in the electrodeposition coating method using the electrode and the electrolysis apparatus of the present invention, the bath temperature can be easily controlled even when the number of processed steel sheets to be electrolyzed is increased, and stable film thickness control is possible. Therefore, the present invention can be applied to a production line for automobile members such as door panels.

  Using the electrolytic apparatus of the present invention, electrodeposition coating was performed on a steel sheet (cold rolled steel sheet).

As pretreatment for electrodeposition coating, degreasing is first performed by immersing in a cold-rolled steel sheet specimen at 40 ° C. in an alkaline degreasing solution: FC-E2001 (manufactured by Nihon Parkerizing Co., Ltd., alkalinity: 18.3 pt or 18.5 pt) for 120 seconds. Treated. Thereafter, a surface conditioning treatment and a zinc phosphate treatment were sequentially performed to form a chemical conversion film having an adhesion amount per side of 3 g / m ² . The surface conditioning treatment was performed by immersing the test piece after the degreasing treatment in a room temperature surface conditioning agent: PL-ZTH (manufactured by Nippon Parkerizing Co., Ltd.) for 20 seconds. Further, the zinc phosphate treatment was performed by immersing in PB-SX35 (manufactured by Nippon Parkerizing Co., Ltd., total acidity 21.5pt, free acidity 0.7pt, accelerator concentration 4.0pt) for 120 seconds. .

After the above pretreatment, electrodeposition coating was performed using the electrolytic apparatus shown in FIG. 1 and a cationic electrodeposition paint as the electrolyte. The counter electrode (electrode) 5 is connected to the anode side of the DC power source 4, and a cold-rolled steel sheet test piece on which a chemical conversion film is formed is used as the working electrode 2. The working electrode 2 is connected to the cathode side, and a voltage is applied between both electrodes. The By applying a voltage as described above, the cationic paint particles in the cationic electrodeposition paint are attracted to the working electrode 2 by electrophoresis, and an electrodeposition coating film is formed on the steel sheet. Each condition is as follows.
Electrodeposition conditions Electrodeposition paint: Trade name GT-100 (manufactured by Kansai Paint Co., Ltd.)
Initial electrodeposition paint temperature (bath temperature): 30 ° C
Load voltage: 100V, 160V, 220V
Energization method: 30 seconds slow start + 2 minutes 30 seconds Constant voltage energization energization time: 3 minutes (including slow start 30 seconds)
Pole ratio: (Cold rolled steel plate specimen (working electrode) area: counter electrode area) is (1: 2)
Distance between electrodes: 15cm
Baking temperature: 170 ° C. (steel plate temperature) × 20 minutes Counter electrode cooling condition Refrigerant: Water (30 ° C.)
Refrigerant flow rate: 0.1 L / s
Refrigerant flow rate: 0.88 m / s
In addition, using the conventional electrolysis apparatus of FIG. 4 as Comparative Example 1, electrodeposition coating was performed in the same manner as in the above example under other conditions. In addition, in the conventional electrolysis apparatus of FIG. 4, the cooling tank was provided in the outer side of the electrolytic cell 3, and it cooled using the refrigerant | coolant. Further, as Comparative Example 2, an electrodeposition coating film was formed using the apparatus of FIG. 1 except that no coolant was allowed to flow inside the counter electrode (electrode) 5 and other conditions were the same as in the above example.

  The test was performed 10 times, and the temperature change rate of the bath temperature was examined. The temperature fluctuation rate was calculated by (10th bath temperature-1st bath temperature) ÷ initial bath temperature (30 ° C.) × 100 (%).

  Moreover, since the electrodeposition coating film thickness also changes when bath temperature changes, the electrodeposition coating film thickness of the 1st time and the 10th time was measured. The electrodeposition coating thickness was measured using an electromagnetic film thickness meter (LZ-200, manufactured by Kett Scientific Laboratory), and one location at the center of the test piece was measured.

  The results obtained as described above are shown in Table 1.

  From Table 1, in the present invention example, the bath temperature was stabilized, and as a result, a uniform electrodeposition coating film thickness was obtained. On the other hand, in the comparative example, the bath temperature was not stable, and the electrodeposition coating film thickness varied.

1: Electrolytic solution 2: Working electrode (electrolyzed sample)
3: Electrolytic cell 4: DC power supply 5: Counter electrode (electrode)
6: Stirring means 7: Refrigerant inlet side 8: Refrigerant outlet side

Claims (6)

  An electrode having cooling means inside.   The electrode according to claim 1, wherein the cooling means cools using water as a coolant.   The electrode according to claim 2, wherein the cooling means has a path through which water flows from the lower part to the upper part.   An electrolysis apparatus comprising: a counter electrode comprising the electrode according to claim 1; and a working electrode.   The electrolysis apparatus according to claim 4, wherein a distance between the counter electrode and the working electrode is changeable.   An electrolysis apparatus according to claim 4 or 5, wherein the counter electrode is an anode, the working electrode is a cathode made of a metal material, and an electrodeposition paint is used as an electrolytic solution, and the electrode material is electrodeposited on the metal material. Dressing method.

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