JP2002134128A - Surface treatment method lowering contact resistance to carbon on passive stage metal surface and its device, and metal member for low contact resistant to carbon solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment method lowering the contact resistance to carbon on a passive state metal surface, capable of producing a passive state metal member having low contact resistance to carbon at a low cost, and to provide its device and a metal member for a low contact resistant to carbon solid polymer fuel cell. SOLUTION: A noble metal is attached to the passive state metal, immediately after a surface oxide film has been removed, by polishing the passive state metal with a polishing material to which the noble metal is attached. The rotating type or belt-type polishing material is preferable. The device is equipped with the rotating type or belt-type polishing material, its driving mechanism, a noble metal pressing jig, and a polishing load control mechanism. The passive state metal is preferably stainless steel containing 11 or higher mass.% of chromium, industrially pure titanium, or a titanium base alloy. The metal member for the low contact resistant to carbon solid polymer fuel cell manufactured by this method, and with this device has a contact resistance to carbon of 100 mΩ.cm2 or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the surface treatment of passive metal members made of stainless steel, titanium, etc., which are required to have low contact resistance with respect to carbon, such as a separator in contact with the current collector carbon of a polymer electrolyte fuel cell. The present invention relates to a surface treatment method and apparatus for reducing the contact resistance of a passive metal surface with respect to carbon so as to reduce the cost.

[0002]

2. Description of the Related Art In recent years, fuel cells for electric vehicles have been developed.
It has begun to progress rapidly with the successful development of solid polymer materials. Unlike conventional alkaline fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid electrolyte fuel cells, solid polymer fuel cells use a hydrogen ion selective permeation type organic membrane as the electrolyte. The fuel cell is characterized by using hydrogen gas obtained by reforming alcohols in addition to pure hydrogen, and electrochemically controlling the reaction with oxygen in the air to generate electric power. It is a battery of the system to take out.

In a polymer electrolyte fuel cell,
Since the solid polymer membrane functions well even when it is thin, and the electrolyte is fixed in the membrane, it functions as an electrolyte if the dew point in the battery is controlled, so that the flow of an aqueous solution electrolyte, molten salt electrolyte, etc. There is no need to use versatile media, and the battery itself can be designed to be compact and simple.

Conventionally, as stainless steel for fuel cells,
JP-A-4-247852, JP-A-4-358044
JP-A-7-188870, JP-A-8-16554
6, JP-A-8-225892, JP-A-8-3116
As disclosed in Japanese Patent No. 20 and other publications, there is a stainless steel for a fuel cell that operates in a molten carbonate environment where high corrosion resistance is required. In addition, Japanese Patent Application Laid-Open No. 6-26419.
3, JP-A-6-293941, JP-A-9-6767
As disclosed in publications such as No. 2, there is a solid oxide fuel cell material that operates at a high temperature of several hundred degrees.

On the other hand, as a constituent material of a polymer electrolyte fuel cell that operates in a region below the boiling point of a cooling aqueous solution, the temperature is not so high, and the corrosion resistance and
Carbon-based materials have been used because they can exhibit sufficient durability.However, with the aim of lowering costs and miniaturization, technological development related to the application of stainless steel and titanium is also progressing. I have.

Japanese Patent Application Laid-Open No. Hei 10-228914 discloses a stainless steel (SU) invented for the purpose of obtaining a fuel cell separator having a small contact resistance with an electrode of a unit cell.
S304) is press-formed to form a bulge formed portion having a large number of irregularities on the inner peripheral portion, and a gold plating having a thickness of 0.01 to 0.02 μm is formed on the bulge tip side end surface of the bulge formed portion. A fuel cell separator characterized by having a layer formed thereon, and as a method of using the same, a fuel cell separator is interposed between stacked unit cells when forming a fuel cell,
A technique in which the electrodes of the unit cell and the gold plating layer formed on the end surface of the bulging portion of the bulging portion are in contact with each other, and a reaction gas passage is defined between the fuel cell separator and the electrode. Is disclosed.

However, when a polymer electrolyte fuel cell was actually manufactured based on this technique, it was found that the following three technical problems were encountered. a) In an environment in a polymer electrolyte fuel cell where long-term durability is required, SUS304, which is a general-purpose steel type, may not be sufficient as an alloy component of a stainless steel separator. Cr, Ni, Mo may be used as a countermeasure. It is necessary to increase the content such as.

B) In the case of stainless steel in which the alloy components such as Cr, Ni, and Mo are increased, the passive oxide film of the stainless steel is formed between the gold plating layer and the stainless steel substrate only by the wet gold plating method during the plating process. It remains without being completely reduced, causing interlayer resistance between the stainless steel and the gold plating layer,
It may cause power loss. As a countermeasure, it is necessary to attach a noble metal while removing the film.

C) The separator is assumed to have a shape in which a bulge formed by a large number of irregularities is formed on the inner peripheral portion by press molding, but an attempt is actually made to process the member having flat portions on four sides. In addition, ductile cracks occur in the bulging molded part consisting of irregularities, and as a countermeasure, it is necessary to set up a multi-step process with low productivity, not necessarily leading to cost reduction, and furthermore, alloy components for improving long-term reliability It is difficult to press-mold a stainless steel having this increased formability into this shape because workability is lower than that of SUS304.

The present inventors have already solved the above-mentioned problems a) and b) by solving the problems described in Japanese Patent Application No. 11-0628.
No. 13, Japanese Patent Application No. 11-170142, Japanese Patent Application 2000-
No. 196526. Regarding the problem (c), measures against the problem are described in Japanese Patent Application No. 2000-081.
315 and Japanese Patent Application No. 2000-143103.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem b) and can produce a passive metal member having a low contact resistance to carbon at low cost. Resistive surface treatment method and apparatus, and
It is an object of the present invention to provide a metal member for a polymer electrolyte fuel cell having a low contact resistance to carbon manufactured by the method.

[0012]

As described above, in order to make the polymer electrolyte fuel cell system widely available to the general public, it is a major problem to reduce the member manufacturing cost to the utmost. In order to satisfy the performance, it is necessary to remove the film and attach the noble metal to a part of the surface of the passive metal having high corrosion resistance.

A method of applying a noble metal using a wet plating method or a dry process method or a method of attaching a noble metal foil requires a large number of processing steps, and inevitably results in a reduction in personnel costs including equipment costs and management overhead costs relative to material costs. The ratio increases, which hinders cost reduction. Therefore, by developing a mechanical surface continuous treatment process that directly attaches and adheres a pure noble metal or its alloy to the passive metal surface, it is possible to omit the processing and treatment process of precious metal raw materials in the middle stage by the conventional method. The present invention has been accomplished, and the gist thereof is as follows.

(1) A passive metal characterized in that a noble metal is attached to the passive metal immediately after removing a surface oxide film by polishing the passive metal with an abrasive to which a noble metal is attached. Surface treatment method with low contact resistance to carbon. (2) The passivation metal is polished with an abrasive to which a noble metal is attached, so that the noble metal is attached to the passivation metal immediately after the surface oxide film is removed, and then the precious metal is further pressed and adhered. A surface treatment method for reducing the contact resistance of a passive metal surface to carbon with respect to carbon.

(3) The surface treatment for reducing the contact resistance of a passive metal surface with respect to carbon as described in (1) or (2) above, wherein the abrasive is a rotary or belt type abrasive. Law. (4) The above-mentioned (1) to (3), wherein the noble metal is continuously supplied and adhered to the abrasive by pressing the noble metal onto the rotary or belt type abrasive.
The surface treatment method for reducing contact resistance of a passive metal surface to carbon with respect to carbon according to any one of the above.

(5) The surface treatment method for reducing contact resistance of a passive metal surface with respect to carbon as described in (2) above, wherein the pressure contact is performed while applying ultrasonic waves. (6) The above (1) to (5), wherein the polishing, adhesion and / or pressure contact are performed in an inert gas.
The surface treatment method for reducing contact resistance of a passive metal surface to carbon with respect to carbon according to any one of the above.

(7) The method according to any one of (1) to (6), wherein the noble metal is gold, platinum, palladium, nickel, copper or an alloy containing at least one of them. Surface treatment method for low contact resistance of passive metal surface to carbon. (8) The above-mentioned (1) to (1), wherein the passive metal is stainless steel, titanium or a titanium-based alloy.
(7) The method for treating a surface of a passive metal with low contact resistance to carbon with respect to carbon according to any one of (7).

(9) A rotary or belt-type abrasive for polishing a passive metal, a drive mechanism for driving the abrasive,
An apparatus for treating a passive metal surface with low contact resistance to carbon, comprising: a jig for pressing a noble metal against the abrasive; and a polishing load control mechanism connected to the jig. (10) The surface treatment apparatus for reducing contact resistance of a passive metal surface with respect to carbon according to (9), further comprising a pressure roll on the exit side of the drive mechanism.

(11) The apparatus further comprises an ultrasonic wave generating means for generating an ultrasonic wave in proximity to the pressure roll, and an ultrasonic wave applying means for applying the ultrasonic wave to the pressure roll. The surface treatment apparatus for reducing contact resistance of a passive metal surface with respect to carbon on carbon as described in (10) above. (12) The method according to any one of (9) to (11), further comprising a shielding means for shielding at least one of the abrasive, the driving mechanism, the jig, and the pressure roll with an inert gas. The surface treatment apparatus for reducing contact resistance of a passive metal surface to carbon with low contact resistance according to any one of the above.

(13) The passive metal surface according to any one of (9) to (12), further comprising a deformation correcting means for correcting deformation of the passive metal. Contact resistance surface treatment equipment. (14) The method according to any one of (9) to (13), further including a dust collection / recovery unit configured to recover and reuse the noble metal powder scattered without adhering to the abrasive. Surface treatment equipment for low contact resistance of passive metal surface to carbon.

(15) A low-polymer, low-contact-resistance solid polymer fuel comprising a passive metal to which a noble metal is attached by removing a surface oxide film and having a contact resistance to carbon of 100 mΩcm ² or less. Metal parts for batteries. (16) The above-mentioned (15), wherein the passive metal is stainless steel, titanium or a titanium-based alloy.
4. The metal member for a polymer electrolyte fuel cell having low contact resistance to carbon according to item 1.

(17) The metal for a polymer electrolyte fuel cell having low contact resistance to carbon according to (16), wherein the stainless steel is a stainless steel containing 11% by mass or more of chromium. Element. (18) The passive metal has been subjected to the surface treatment of the passive metal surface according to any one of (1) to (8) by the surface treatment method for reducing contact resistance to carbon. The metal member for a polymer electrolyte fuel cell having low contact resistance to carbon according to any one of (15) to (17).

(19) The passivating metal according to (9),
(15) The passive metal surface according to any one of (15) to (14), which has been surface-treated by a surface treatment device for reducing contact resistance to carbon with respect to carbon. Metal member for polymer electrolyte fuel cells with low contact resistance to carbon.

[0024]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below.
FIG. 1 shows an example of an apparatus belonging to the present invention, and the method and apparatus of the present invention will be described with reference to FIG. FIG.
Is an example of an apparatus using a belt-type abrasive. As the belt-type abrasive, a commercially available belt-type abrasive cloth or belt-type abrasive paper is used. The polishing may be performed as long as continuous polishing is possible. For example, a rotary abrasive may be used instead of the belt-type abrasive.

The belt type abrasive 2 is rotating at a predetermined speed while being given a constant tension by the rolls 1 and 3. The rotation direction is opposite to the feed direction of the passive metal 14 because polishing is performed. The noble metal block 5 is held by a holding jig 6 and pressed against the belt type abrasive 2 by a load transmitting jig 7. The load transmitting jig 7 is connected to a polishing load control mechanism (not shown).

The noble metal is attached and supplied to the belt type abrasive 2 from the pressed noble metal block 5. Of the noble metals pulverized by the abrasive, the powder that has not adhered is collected by the negative pressure dust cover 4 and the negative pressure dust cover 8 for reuse. In the case of this apparatus, for example, the collected gas is guided to a cyclone classifier to separate and collect the noble metal powder. Particularly when expensive precious metals are used, it is preferable to provide such a recovery means from the viewpoint of cost.

In the apparatus shown in FIG. 1, a set of the above-described apparatuses is provided in opposition to each other. A coil, a hoop, or a cut plate or foil-shaped passive metal 14 having a predetermined length is attached to the passive metal 14. By applying a predetermined load so as to sandwich the metal 14, the noble metal is adhered to the passive metal immediately after the surface oxide film is removed by the abrasive material to which the noble metal has been attached, and the passive metal surface has low contact with carbon. A resistance surface treatment is performed.

As shown in FIG. 1, a pressure roll 9 can be further provided to further enhance the adhesion of the attached noble metal. In this case, an ultrasonic wave can be applied to the pressure roll 9. The application of the ultrasonic wave can effectively improve the adhesion of the attached noble metal. These processes are
An inert gas can be more reliably adhered and pressed under pressure while preventing the oxide film from reforming on the surface of the passive metal from which the oxide film has been removed by polishing. A shield box 10 can be provided.

In the passive metal 14, the upstream rolling and
There is a possibility that internal stress may be accumulated during the annealing / cleaning process, and a slight deformation may be added after the above-mentioned surface treatment process. Therefore, the shape correcting rolls 11, 12, and 13 can be provided for the purpose of continuously performing the correction.

In these series of apparatuses, the belt-type polishing cloth or the rotary grindstone rotates in a direction in which the workpiece is driven in a reverse direction to the traveling direction of the workpiece. Although not shown, a driving roll may be separately provided, and the pressing roll 9 and the shape correcting rolls 11, 1
The driving may be performed in the forward direction using 2 and 13. The area of the portion to be processed is preferably limited to a portion in contact with the carbon paper current collector in a state used as a separator in terms of cost reduction by suppressing the amount of noble metal attached, and a belt-type abrasive or a rotary grindstone is preferable. By performing the intermittent treatment by controlling the width of the contact and the contact / separation conditions, it is possible to perform the surface treatment to a necessary minimum area.

It is not always necessary to treat both surfaces of the material to be treated, and if only one side is required, there is an option to apply a naked roll to the opposite side of the surface to be treated and rotate it freely. . The passive metal 14 is assumed to be a passive metal coil, a hoop, a cut plate, or a foil, but the shape is not limited, and the passive metal 14 may be processed into a separator shape.

The kind of the noble metal to be deposited is gold or an alloy containing gold, platinum or an alloy containing platinum, palladium or an alloy containing palladium, nickel or an alloy containing nickel, or an alloy containing copper or copper. It is effective in reducing the contact resistance. Although affected by the market price, it is preferable to use gold or a gold alloy in consideration of compatibility between corrosion resistance and cost.

As a specific type of the passive metal, stainless steel, titanium or a titanium-based alloy is practically preferable. In particular, the stainless steel is preferably a stainless steel containing 11% by mass or more of chromium, and the titanium is preferably industrially pure titanium. The passive metal member manufactured by the present invention preferably has a contact resistance value with respect to carbon of 100 mΩcm ² or less. When heat generated by energization is effectively used for heating water, as in a co-generator, etc., a contact resistance of about 100 mΩcm ² or less is sufficient. Since the efficiency is high, a contact resistance of 10 mΩcm ² or less may be required for an application such as an automobile. Therefore, it is necessary to select the type of the noble metal and the like according to the required contact resistance level.

[0034]

EXAMPLES The present invention will be described in more detail with reference to Examples. Note that the following device configuration and manufacturing conditions are merely examples for showing the effects of the present invention, and the present invention is not limited to these. An actual device was prototyped based on the schematic diagram shown in FIG. The width of the belt-type abrasive 2 is 200 mm, the roll radius of the roll 1, the pressure roll 9, and the straightening rolls 11, 12, and 13 is 15 mm, the roll radius of the roll 3 is 30 mm, and the center distance between the roll 1 and the roll 3 is 200 mm.
And Pure gold was used for the noble metal block 5, and the contact area with the abrasive was 200 × 5 mm.

The polishing / transfer device and the pressure roll can be moved up and down, and the load can be controlled. The material of the straightening rolls 11, 12, and 13 is hard rubber, and the material to be processed is driven in the forward direction by this rotation. A stainless steel roll is used for the pressure roll 9, so that wear and seizure do not occur. In addition, the material to be processed can be freely rotated in conjunction with the movement of the material to be processed, and ultrasonic vibration can be applied as required. Line speed is 50mm
/ Sec.

Silicon carbide is in close contact with the belt-type polishing cloth 2, and is # 600 and # 1000 as counts.
Was used. The rotation of the polishing / transfer device was performed by the roll 1. In this polishing / transfer apparatus, it was possible to replace the rotating body of the belt-type polishing cloth with a rotating grindstone having a width of 200 mm and a radius of 15 mm, and a test on its application was also conducted.

The length of a sample produced using the prototype surface treatment apparatus for reducing contact resistance to carbon was 300 mm.
mm, the contact resistance with carbon paper was measured under a load condition of 10 kgf / cm ² , or the same contact resistance was measured by a steam oxidation test in which the film was exposed to steam at 100 ° C. for 1000 hours. Tables 1 to 8 show test results under various conditions.

From these results, it can be seen that the contact resistance between ordinary stainless steel or titanium and carbon paper is about 600 mΩcm ² , but stainless steel (SUS316L) treated by the method of the present invention or industrial pure titanium (CP-Ti )
Shows that a low contact resistance value is realized on an order, and it can be determined that the contact resistance value reaches a level usable for a separator for a polymer electrolyte fuel cell.

The tendency is that the greater the polishing / transfer load and the pressure roll load, the lower the contact resistance, and if an inert gas shield with argon or ultrasonic treatment is applied, the contact resistance after steam oxidation increases. Is suppressed.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

[Table 8]

[0048]

As the awareness of environmental preservation has increased, the transition from the current internal combustion engine using fossil fuels to electric drive type automobiles using polymer electrolyte fuel cells using hydrogen and distributed cogeneration systems has become a worldwide trend. Is being considered. To make these new technologies widely available to the general public, we need to develop technologies for cost reduction and high reliability.
It is necessary to promote including the fuel supply system.

The present invention, among the many problems in this field, is a low-cost surface treatment method for reducing the contact resistance of carbon to high corrosion-resistant stainless steel or titanium used as a separator for polymer electrolyte fuel cells. There is significance in making it possible, and it is extremely effective as a technology for realizing a polymer electrolyte fuel cell.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a surface treatment apparatus for reducing contact resistance of a passive metal surface with respect to carbon.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Roll 2 ... Belt type abrasive 3 ... Roll 4 ... Negative pressure dust collecting cover 5 ... Precious metal block 6 ... Holding jig 7 ... Load transmission jig 8 ... Negative pressure dust collecting cover 9 ... Pressure roll 10 ... Non Active shield box 11 ... straightening roll 12 ... straightening roll 13 ... straightening roll 14 ... passive metal (before treatment) 15 ... passive metal (treated)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toru Utsumi 5-3 Tokai-cho, Tokai-shi, Aichi F-term in Nippon Steel Corporation Nagoya Works (reference) 5H026 AA06 BB00 CC03 EE02

Claims (19)

[Claims] 1. A passive metal surface, wherein a noble metal is attached to the passive metal immediately after removing a surface oxide film by polishing the passive metal with an abrasive to which a noble metal is attached. Surface treatment with low contact resistance to carbon. 2. The passivation metal is polished with an abrasive to which a noble metal has been adhered, whereby the noble metal is adhered to the passivation metal immediately after the surface oxide film is removed, and then the noble metal is further added. A surface treatment method for reducing the contact resistance of a passive metal surface with respect to carbon, which is characterized by pressure contact. 3. The method of claim 1, wherein the polishing material is a rotary or belt type polishing material. 4. The precious metal is continuously supplied to and adhered to the abrasive by pressing the precious metal against the rotary or belt type abrasive.
4. The surface treatment method of claim 3, wherein the surface of the passive metal has a low contact resistance with respect to carbon. 5. The surface treatment method according to claim 2, wherein the pressure contact is performed while applying an ultrasonic wave. 6. The method according to claim 1, wherein said polishing, adhesion and / or pressure contact are performed in an inert gas.
The surface treatment method for reducing the contact resistance of a passive metal surface with respect to carbon on carbon as described in any one of the above items. 7. The method according to claim 1, wherein the noble metal is gold, platinum, palladium,
The surface treatment method for reducing the contact resistance of a passive metal surface with respect to carbon, according to any one of claims 1 to 6, wherein the surface treatment is nickel, copper or an alloy containing at least one of them. 8. The method according to claim 1, wherein the passive metal is stainless steel, titanium or a titanium-based alloy.
8. The surface treatment method for reducing contact resistance of a passive metal surface with respect to carbon on carbon according to any one of claims 7 to 7. 9. A rotary or belt type abrasive for polishing a passive metal, a drive mechanism for driving the abrasive, a jig for pressing a noble metal against the abrasive, and a polishing tool connected to the jig A surface treatment apparatus for reducing contact resistance of a passive metal surface with respect to carbon, comprising a load control mechanism. 10. The surface treatment apparatus of claim 9, further comprising a pressure roll on the exit side of the driving mechanism. 11. Further, in the vicinity of the pressure roll,
11. The low contact resistance of a passive metal surface with respect to carbon according to claim 10, further comprising: an ultrasonic wave generating means for generating an ultrasonic wave; and an ultrasonic wave applying means for applying the ultrasonic wave to a pressure roll. Surface treatment equipment. 12. The apparatus according to claim 9, further comprising a shield means for shielding at least one of the abrasive, the driving mechanism, the jig, and the pressure roll with an inert gas. The surface treatment apparatus for reducing the contact resistance of a passive metal surface to carbon with respect to carbon according to claim 1. 13. The apparatus according to claim 9, further comprising a deformation correcting means for correcting deformation of the passive metal.
13. The surface treatment apparatus for low contact resistance of carbon on a passive metal surface according to any one of items 12 to 12. 14. The dust collecting and separating means for collecting and reusing noble metal powder scattered without adhering to the abrasive material, the dust collecting and separating means being provided. Surface treatment equipment for low contact resistance of passive metal surface to carbon. 15. A passive metal to which a noble metal is adhered by removing a surface oxide film and has a contact resistance to carbon of 10
A metal member for a polymer electrolyte fuel cell having low contact resistance to carbon, wherein the metal member has a resistance of 0 mΩcm ² or less. 16. The metal member for a polymer electrolyte fuel cell with low contact resistance to carbon according to claim 15, wherein the passive metal is stainless steel, titanium or a titanium-based alloy. 17. The metal member for a polymer electrolyte fuel cell having low contact resistance to carbon according to claim 16, wherein the stainless steel is a stainless steel containing 11% by mass or more of chromium. 18. The passive metal has been subjected to a surface treatment by the surface treatment method for reducing the contact resistance of carbon to carbon on a passive metal surface according to any one of claims 1 to 8. The metal member for a polymer electrolyte fuel cell having low contact resistance to carbon according to any one of claims 15 to 17. 19. The passive metal has been subjected to a surface treatment by the surface treatment apparatus for reducing contact resistance of carbon to carbon with respect to a passive metal surface according to claim 9. The metal member for a polymer electrolyte fuel cell having low contact resistance to carbon according to any one of claims 15 to 17.