JPH07173699A - Gas diffusion electrode device for electroplating - Google Patents

Abstract

PURPOSE:To facilitate the exchange and repair of electrodes and improve air permeability and gas hermeticity by forming grooves having a circular section on the discharge surface side of a conductive unit frame, inserting the peripheral edges of thin films into these grooves and fixing the thin films by means of O-rings. CONSTITUTION:Plural pieces of tap holes 4 are formed in conductive unit frames 3 of plural pieces of unit electrodes 2 constituting a gas diffusion electrode device so that these unit electrodes 2 are easily mounted. Each unit electrode 2 consists of the conductive unit frame 3, the thin film 6 mounted at this frame and a current collector 7 in contact with a power feeder. The peripheral edge of the thin film 6 is inserted into the groove 8 of the circular section formed on the discharge surface side of the conductive unit frame 3 and is fixed by the expandable O-ring 10. Plural pieces of the unit electrodes 2 are preferably mounted to electrode holders 1 zigzag in at least two rows in the moving direction of objects to be plated.

Description

Detailed Description of the Invention

[0001]

This invention relates to an electroplating tank,
It relates to a gas diffusion electrode device arranged as an anode.

[0002]

2. Description of the Related Art When an electroplating method is used to electroplate an object to be plated, which moves continuously, such as a metal strip, as an anode, an insoluble electrode that does not wear itself is used as an anode. However, plating is often performed in a sulfate electroplating solution.

However, in order to save energy and improve efficiency, when electroplating is performed at a high current density, when an insoluble anode is used and electroplating is performed in a chloride electroplating solution, harmful chlorine is generated from the insoluble anode. The problem of gas generation arises. Even if sulfuric acid electroplating solution is used to avoid the generation of chlorine gas,
Since a large amount of oxygen gas generated from the anode is always present between the anode and the cathode, the apparent electrical conductivity of the plating solution is lowered, and there is a problem that the plating coating itself is adversely affected.

As a means for solving the above-mentioned problems, a gas diffusion electrode in which a gas diffusion layer and a reaction layer are joined is arranged as an anode in an electroplating tank, and the reaction layer side of the gas diffusion electrode is filled with a plating solution. Then, hydrogen gas is supplied to the gas diffusion layer side of the gas diffusion electrode, the hydrogen gas is oxidized and diffused in the plating solution, and thereby electroplating is performed on the surface of the continuously moving metal strip. An electroplating method using a gas diffusion electrode is known, and in JP-A-3-188299, as an electrode device used in such a method, a thin film in which a gas diffusion layer and a reaction layer are bonded to an electrode holder is used. A supported gas diffusion electrode device (hereinafter referred to as prior art) is disclosed.

[0005]

However, the prior art has the following problems. That is, the gas diffusion electrode has a thickness of 100 μm in which a gas diffusion layer composed of hydrophobic carbon black and a fluororesin and a reaction layer composed of hydrophilic carbon black carrying a catalyst and a fluororesin are joined.
Since it is composed of a thin film of m, it has poor rigidity and is easily damaged. Therefore, the electrodes must be replaced and repaired frequently, the replacement and repair work is not easy, the repair cost increases, and there are many problems in terms of electrical conductivity and gas tightness.

Therefore, an object of the present invention is to provide an efficient and economical gas diffusion electrode device which solves the above-mentioned problems, is easy to replace and repair, and is excellent in electrical conductivity and gas tightness. To do.

[0007]

The present invention relates to a gas diffusion electrode device in which a thin film in which a gas diffusion layer and a reaction layer are joined is supported by an electrode holder, wherein the gas diffusion electrode device is attached to the electrode holder. The unit electrode is composed of a plurality of unit electrodes detachably attached in one or more rows, each of the unit electrodes including a conductive unit frame, a thin film attached to the unit frame, and a current collector in contact with the power supply body. On the discharge surface side of the conductive unit frame, a groove having a circular cross section is continuously formed over the entire circumference thereof, and the thin film is expandable by inserting the peripheral edge thereof into the groove. O
It is characterized by being fixed to the conductive unit frame by a ring.

The plurality of unit electrodes are preferably attached to the electrode holder in a zigzag manner in at least two rows in the moving direction of the object to be plated. Further, the power feeding body, which is attached to the electrode holder and is in contact with the current collectors of the plurality of unit electrodes, is a power feeding rod rotatable about its axis. A notch having a width substantially equal to the width is formed stepwise in the lengthwise direction of the power feeding rod, or the power feeding body is a plate-shaped power feeding plate that is horizontally movable in the widthwise direction. A notch having a width substantially equal to the width of the current collector is formed in the width direction of the plate in a stepwise manner in the length direction of the power feeding plate so that the plating current for the object to be plated can be controlled. Good.

[0009]

The gas diffusion electrode device of the present invention comprises a plurality of unit electrodes removably attached to the electrode holder in one or more rows, and the thin film constituting each unit electrode is made of a conductive unit frame. On the discharge surface side, a peripheral edge is inserted into a groove having a circular cross section formed over the entire circumference, and is fixed by an inflatable O-ring. Therefore, replacement and repair are easy, and the electrical conductivity and gas tightness are excellent.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic plan view of a gas diffusion electrode device of the present invention, FIG. 2 is a schematic perspective view seen from the holder side of an electrode piece, FIG. 3 is a schematic perspective view seen from the plating solution side, and FIG. 4 is a sectional view taken along the line AA of FIG. As shown in FIG. 1, the gas diffusion electrode device of the present invention comprises a plurality of unit electrodes 2 detachably attached to an electrode holder 1 in one row. The conductive unit frame 3 of the unit electrode 2 has a plurality of tap holes 4 formed therein. By inserting the tap holes 4 into a bolt 5 having corrosion resistance and insulation attached to the electrode holder 1, The electrode 2 can be easily and easily attached to the electrode holder 1.

As shown in FIGS. 2 to 4, the unit electrode 2
Is the conductive unit frame 3 and the thin film 6 attached to it.
And a current collector 7 that contacts the power supply. The conductive unit frame 3 is, for example, made of copper having a rectangular cross section coated with titanium in order to improve conductivity and corrosion resistance,
It has a small square shape of 50 x 200 mm. On the discharge surface side of the conductive unit frame 3, a groove 8 having a circular cross section is continuously formed over the entire circumference thereof, and the inner surface of the groove 8 is plated with platinum to enhance the electrical conductivity. . The discharge side of the unit frame 3 is covered with a corrosion-resistant insulating material 9 such as a rubber lining. The current collector 7 is made of copper and is provided so as to project toward the holder.

The thin film 6 is composed of a gas diffusion layer made of hydrophobic carbon black and a fluororesin, and a reaction layer made of hydrophilic carbon black carrying a catalyst and a fluororesin, which are joined together. Is inserted into a groove 8 having a circular cross section provided on the discharge surface side of the conductive unit frame 3, and is fixed by an inflatable O-ring 10.

The O-ring 10 is composed of an expandable and contractible tube, for example, as shown in FIG. Therefore, when a thermosetting or age-hardening resin 10 'is injected into a syringe or the like, the O-ring 10 expands to the full volume of the groove 9 as shown in FIG. Therefore,
The peripheral edge of the thin film 6 inserted into the groove 8 is pressed firmly against the periphery of the thin film 6, whereby the thin film 6 can be easily and reliably fixed to the conductive unit frame 3.

A plurality of unit electrodes 2 having the above structure
As shown in FIG. 1, if the unit electrodes 2 are attached in a row to the electrode holder 1 that also serves as a gas chamber to which hydrogen gas is supplied, even if the unit electrodes 2 are brought into close contact with each other, the thin film 6 of the unit electrode 2
It is inevitable that a gap corresponding to the unit frame 3 is formed between them. As a result, as shown in FIG. 7, in the metal strip A which is the object to be plated, unevenness with a small amount of plating adhered, which corresponds to the above-mentioned gap, occurs, and a plurality of streaks are formed in the length direction of the strip. , The product appearance deteriorates.

Therefore, FIG. 8 is a schematic plan view, and FIG.
As shown in the sectional view taken along the line A-A of FIG. 1, the plurality of unit electrodes 2 can be attached to the electrode holder 1 in a zigzag manner in at least two rows with respect to the moving direction of the metal strip A to be plated. preferable. In this way, the plurality of unit electrodes 2 are attached to the electrode holder 1 in a zigzag manner, so that the lengthwise direction of the metal strip due to the above-mentioned gaps formed between the thin films 6 of the plurality of unit electrodes 2. No streaks occur, and therefore deterioration of the appearance of the product can be prevented.

As shown in the schematic front view of FIG. 10 and the schematic perspective view of FIG. 11, the electrode holder 1 is arranged so as to come into contact with the current collectors 7 of the plurality of unit electrodes 2 mounted on the electrode holder 1. A power feeding rod 11 as a power feeding body is provided across the width direction. A plating current is supplied from the power supply rod 11 to each of the plurality of unit electrodes 2 through each current collector 7 in contact therewith.

In the example shown in FIGS. 10 and 11, the power feeding rod 11 as a power feeding member is formed of a rod-shaped body rotatable about its axis. A plurality of cutouts 12 are formed in the power feeding rod 11 in the circumferential direction. Cutout
The reference numeral 12 has a width substantially equal to the width of the current collector 7, and is formed stepwise from the central portion of the power feeding rod 11 where the notch is not formed to both ends thereof.

Therefore, the power feeding rod 11 is provided with the notch 12
When all of the parts where no is formed are in contact with the current collectors 7 of the plurality of unit electrodes 2,
A plating current can be passed over all of the plurality of unit electrodes 2. When the power supply rod 11 is slightly rotated, the power supply rod 11 is not in contact with the current collectors 7 of the unit electrodes 2 at both ends due to the first step cutouts 12 at both ends thereof. Further, when the power feeding rod 11 is rotated, the power feeding rod 11 is not connected to the current collectors 7 of the two unit electrodes 2 at both ends by the first and second stepped notches 12 at both ends thereof. Get in touch. Thereafter, in the same manner, the non-contact state can be successively formed from the both ends of the plurality of unit electrodes 2 by the rotation of the power feeding rod 11.

1 as an anode provided in the plating layer
When the metal strip is continuously moved between the pair of gas diffusion electrodes, and when the electroplating film is formed on the surface of the metal strip by the gas diffusion electrode, the plating current is concentrated on both ends in the width direction of the metal strip. A so-called overcoat occurs in which the amount of plating adhered on both ends of the metal strip is excessive. In order to prevent such overcoating, conventionally, an edge mask whose position is variable according to the plate width of the metal strip is provided in the plating tank, and the plating current can be interrupted by this edge mask. It was done.

However, if the feeding rod 11 is rotated as described above and the feeding of the plating current to each current collector 7 of the plurality of unit electrodes 2 is controlled in accordance with the width of the metal strip A, the inside of the plating layer is controlled. The overcoat can be appropriately prevented without installing the above-mentioned edge mask.

FIG. 12 is a schematic plan view showing another example of the power feeding body. In this example, the power supply body is composed of a plate-shaped power supply plate 13 extending in the width direction of the electrode holder 1. A plurality of cutouts 14 are formed in the width direction of the power supply plate 13 from the center to both ends. The notch 14 has a width that is substantially equal to the width of the current collector 7, and is formed in a stepwise manner from the central portion of the power supply plate 13 where the notch is not formed to both ends thereof.

The power supply plate 13 is horizontally movable in the width direction by a drive mechanism (not shown). Therefore,
When the power supply plate 13 is positioned so that all the portions where the notches 14 are not formed are in contact with the current collectors 7 of the plurality of unit electrodes 2, a plating current flows through all of the plurality of unit electrodes 2. be able to. Power supply plate 13
Is moved slightly horizontally, the first-stage notches on both ends
Due to 14, the power supply plate 13 is not in contact with the current collectors 7 of the unit electrodes 2 at both ends. Further, when the power feeding plate 13 is moved horizontally, the first and second notches 14 at both ends thereof are formed.
As a result, the power supply plate 13 is not in contact with the current collectors 7 of the two unit electrodes 2 at both ends. Thereafter, in the same manner, the horizontal movement of the power supply plate 13 allows the plurality of unit electrodes 2 to be successively formed in a non-contact state from both ends thereof. Therefore, as described above, overcoating can be appropriately prevented without disposing an edge mask in the plating layer.

[0023]

As described above, according to the present invention,
An efficient and economical gas diffusion electrode that is easy to replace and repair and has excellent electrical conductivity and gas tightness is obtained, and a uniform amount of electroplated film is formed on the surface of the object to be plated. It is possible to bring about an industrially useful effect.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a gas diffusion electrode device of the present invention.

FIG. 2 is a schematic perspective view of a unit electrode of the device of the present invention viewed from the holder side.

FIG. 3 is a schematic perspective view of a unit electrode of the apparatus of the present invention as viewed from the plating solution side.

4 is a cross-sectional view taken along the line AA of FIG.

FIG. 5 is a schematic partial front view showing a contracted state of the O-ring used in the present invention.

FIG. 6 is a schematic partial front view showing an expanded state of an O-ring used in the present invention.

FIG. 7 is a diagram showing a coating amount of a metal strip.

FIG. 8 is a schematic plan view showing how a plurality of unit electrodes are attached to an electrode holder.

9 is a cross-sectional view taken along the line AA of FIG.

FIG. 10 is a schematic front view showing a contact state between a current collector of a unit electrode and a power feeding rod as a power feeder.

FIG. 11 is a schematic perspective view showing a contact state between a current collector of a unit electrode and a power feeding rod as a power feeder.

FIG. 12 is a schematic plan view showing another example of the power feeding rod 11.

[Explanation of symbols]

 1 electrode holder, 2 unit electrode, 3 unit frame, 4 tap hole, 5 bolt, 6 thin film, 7 current collector, 8 groove, 9 insulating material, 10 O ring, 10 'resin, 11 power supply rod, 12 notch, 13 power supply plate, 14 notches.

Claims (4)

[Claims] 1. A gas diffusion electrode device in which a thin film in which a gas diffusion layer and a reaction layer are joined is supported by an electrode holder, wherein the gas diffusion electrode device is detachably attached to the electrode holder in one row. Each of the unit electrodes is composed of a conductive unit frame, a thin film attached to the conductive unit frame, and a current collector in contact with the power supply body. On the discharge surface side of the frame, a groove having a circular cross section is continuously formed over the entire circumference, and the thin film has a peripheral edge inserted into the groove, and an expandable O-ring allows the conductive unit to be formed. A gas diffusion electrode device characterized by being fixed to a frame. 2. The device according to claim 1, wherein the plurality of unit electrodes are attached to the electrode holder in a zigzag manner in at least two rows in the moving direction of the object to be plated. 3. The power supply body, which is in contact with the current collectors of a plurality of unit electrodes attached to the electrode holder,
The power feeding rod is rotatable about its axis, and the power feeding rod is provided with a notch having a width substantially equal to the width of the current collector in the circumferential direction thereof in the longitudinal direction of the power feeding rod. The device of claim 1, wherein the device is shaped like a circle. 4. The power supply body contacting the current collectors of a plurality of unit electrodes attached to the electrode holder,
The power supply plate is a plate-shaped power supply plate that can move horizontally in the width direction, and the power supply plate has a notch having a width substantially equal to the width of the current collector in the width direction. The device according to claim 1, wherein the device is formed stepwise in the direction.