JP5580444B2 - Manufacturing method of fuel cell separator - Google Patents

Description

The present invention relates to a method for manufacturing a fuel cell separator, and more particularly to a technique for shortening a process in manufacturing a metal separator.

  As a fuel cell, a laminated body in which separators are laminated on both sides of a flat membrane electrode assembly (MEA) is used as a unit cell, and a plurality of unit cells, for example, several hundred layers are laminated to form a fuel cell stack. A fuel cell configured as is known. The membrane electrode structure has a three-layer structure in which an electrolyte membrane made of an ion exchange resin or the like is sandwiched between a pair of electrodes constituting a positive electrode (air electrode, cathode) and a negative electrode (fuel electrode, anode). According to such a fuel cell, for example, when a fuel gas is caused to flow through a gas passage facing the gas diffusion electrode on the fuel electrode side and an oxidant gas is caused to flow through a gas passage facing the gas diffusion electrode on the air electrode side, A chemical reaction occurs, generating electricity.

  Here, as a separator for a fuel cell, since high conductivity is required, a carbon plate is cut to form a flow path for a gas or a cooling medium, or a metal plate is press-formed. ing. In particular, in recent years, as development as an energy source for transportation means such as automobiles has progressed, it has become necessary to reduce the size of the fuel cell itself, and the development of metal separators that can be made thinner is promoted. ing.

  Here, in the reaction of the fuel cell, water is generated and the proton (H +) is responsible for charge transfer in the electrolyte membrane, so that an acidic atmosphere is formed inside the fuel cell. Therefore, when using a metal separator, it is necessary to ensure corrosion resistance as well as conductivity. Although stainless steel can be used as the metal material having excellent corrosion resistance, there is a disadvantage that the surface of the stainless steel is inferior in conductivity because a passive film exists on the surface. Therefore, in Patent Document 1, the unevenness is formed on the stainless steel plate by press forming, and then etching (acid treatment) is performed to uniformly rebuild the passive film over the entire material, and then the conductivity of the separator is required. Part of the passive film is removed by mechanical polishing, and noble metal plating is applied to the part. In the case where etching is not performed, there is a problem that plating easily deposits on a defect of a passive film caused by press molding or the like, and a noble metal is deposited even on an unnecessary portion.

WO2006 / 129806

  However, the technology described in Patent Document 1 and the like requires etching for re-creating the passive film uniformly and a mechanical polishing process for removing the passive film in the portion where noble metal plating is performed. There is a problem that it takes a lot of production time.

  Accordingly, an object of the present invention is to provide a method of manufacturing a fuel cell separator that does not require etching and mechanical polishing of the separator, and that can omit production equipment and production time.

  The present inventors diligently studied a technique for plating a conductive metal on a separator by omitting etching and mechanical polishing. As a result, the inventors focused on strike plating, which is generally performed as a pretreatment before plating. Strike plating is a method in which current is passed at a high density in a dilute plating solution, and hydrogen is generated on the surface of stainless steel, which is a cathode, due to water electrolysis. At that time, when the experiment was repeated under the hypothesis that hydrogen would contact the stainless steel and reduce the passive film, the passive film was removed by strike plating, and the conductive metal was removed. It was found that plating was deposited.

The manufacturing method of the separator for a fuel cell of the present invention is based on the above knowledge, and includes a press molding process for forming a metal material plate with a concavo-convex shape, and a projection of the material plate formed with a concavo-convex shape. A plating step of plating a conductive metal only on the portion, and the plating step is performed by bringing a plating solution holding material holding a plating solution containing conductive metal ions into contact with only the convex portion, and the plating solution holding material and the material plate Is formed by energizing at a predetermined current density ( excluding an average current density of 5 to 26 A / dm ² ) and generating hydrogen on the surface of the material plate to form the surface of the material plate with the hydrogen. The conductive plate is plated with a conductive metal while reducing the passive film.

In the method for manufacturing the fuel cell separator, plating can be selectively performed on the convex portion by performing plating by bringing the plating solution holding material into contact with only the convex portion. Therefore, it is possible to suppress the deposition of noble metal on unnecessary portions other than the convex portions even in the presence of defects in the passive film due to press formation, so that conventionally required etching can be omitted. it can. Furthermore, since the plating is performed under the condition of generating hydrogen on the surface of the material plate, the passive film can be reduced and removed simultaneously with the plating, and mechanical polishing that has been conventionally required is unnecessary. Therefore, a process can be shortened compared with the conventional plating method, and manufacturing cost can be reduced. In addition, in order to improve the insulation as a separator more, you may rebuild a passive film by performing an etching and heat processing before a plating process as needed. Even in this case, since the mechanical polishing treatment is unnecessary, the manufacturing process can be simplified.

In the present invention, the configuration of the plating solution holding material is arbitrary. For example, a roller in which the surface of a roll made of a conductive material is covered with a porous material can be used. In this case, cloth, sponge, rubber or the like can be used as the porous material, and urethane or polyvinyl alcohol (PVA) can be used as the material of the sponge. Further, as the material of the roll, carbon, Ti—Pt alloy, Ti—Au alloy, or Ti _{2 in} which Ir ₂ O ₃ is dispersed can be used. Then, the porous material is impregnated with the plating solution, and the front and back of the material plate on which the unevenness is formed by press molding is sandwiched between rollers. In this state, by rotating the roller while energizing the roll and the material plate, the strike plating is continuously performed on all the uneven portions. In the present invention, as the conductive metal, a metal having corrosion resistance against an acidic atmosphere inside the fuel cell can be used, and gold or platinum is preferably used.

  In the case of a metal separator, one side of the separator may contact the membrane electrode structure, and the other side may be used as a cooling water flow path. In this case, since it is not necessary to plate the other surface with a conductive metal, it is sufficient to impregnate only the porous material of one roller with the plating solution and energize between the roll and the material plate.

  Moreover, the stamp which provided the porous material in the single side | surface of the flat plate comprised with the electroconductive material similar to the above can be used. Then, the porous material is impregnated with the plating solution, and the front and back of the material plate on which the unevenness is formed is sandwiched between stamps. By energizing the flat plate and the material plate in this state, strike plating can be performed on all of the convex and concave portions at once. Even in such an embodiment, it is possible to impregnate only the porous material of one stamp with the plating solution and to energize between the stamp and the material plate.

  Furthermore, a brush with a hair tuft fixed to the tip of a shaft made of a conductive material can be used. Then, the plating solution is impregnated at the tip of the brush, the brush is brought into contact with the uneven convex portion, and the shaft and the material plate are energized to perform the strike plating on the uneven convex portion.

  According to the present invention, it is not necessary to perform mechanical polishing on the plating portion of the separator, and production equipment and production time therefor can be omitted, and the surface property of the separator is not deteriorated and adhesion to the plating layer is improved. The effect that it can be made is acquired.

It is a figure explaining the main processes of one Embodiment of this invention. It is a side view which shows the plating apparatus for implementing the process of one Embodiment of this invention. It is a side view which shows the plating apparatus in one Embodiment of this invention. It is a side view which shows the other example of the plating apparatus for implementing the process of one Embodiment of this invention. It is a figure which shows the other example of the plating apparatus in other embodiment of this invention, Comprising: (A) is a perspective view of a roller, (B) is a front view of a roller. It is a flowchart which shows the separator manufacturing process of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a manufacturing method of a fuel cell separator according to an embodiment, and FIG. 2 is a view showing a plating apparatus A for carrying out the manufacturing method. As shown in FIG. 6, the main processes performed in this manufacturing method are a press molding process and a gold plating process. Hereinafter, each process is demonstrated in order.

1. Press forming step The press forming step is a step for forming the material plate 10 into a concave-convex shape (cross-sectional wave shape) by press forming, and the material plate 10 has a desired shape as shown in FIG. For example, stainless steel (SUS304 or the like) having a thin plate shape cut to a length is used. By subjecting this material plate 10 to press working, as shown in FIG. 1 (B), predetermined portions of the material plate 10 are formed in a concavo-convex shape, and have a convex portion 11 formed.

  Next, each step after the press forming step is performed by a plating apparatus A shown in FIG. In the plating apparatus A, a degreasing stage 20, a rinsing stage 30, and a gold plating stage 40 are sequentially provided from the upstream side to the downstream side, and the material plate 10 is processed at each stage while being conveyed by the roller conveyor 50.

2. Degreasing / Washing Step In the degreasing step, for example, in the degreasing stage 20, a strong alkaline degreasing agent is brought into contact with the material plate 10, and the oil and fat adhering to the surface of the material plate 10 is removed. In the water washing step, a water shower is sprayed on the material plate 10 in the water washing stage 30 to perform water washing.

3. Gold Plating Step The gold plating step is a step of removing the passive film 12 on the convex portion 11 of the material plate 10 and applying gold plating K thereto. FIG. 3 shows a stamp 41 provided on a gold plating stage 60. The stamp 41 is provided with a porous material 43 on one side of a flat plate 42 made of a conductive material, and a shaft 44 at the center of the flat plate 42. It is fixed and outlined.

As the material of the flat plate 42, carbon, a Ti—Pt alloy, a Ti—Au alloy, a material in which Ir ₂ O ₃ is dispersed in Ti, or the like is used. As the material of the porous material 43, cloth, sponge, rubber or the like is used, and as the material of the sponge, urethane or polyvinyl alcohol (PVA) is used. In addition, means (not shown) for supplying a plating solution to the porous material 43 is provided. The stamp 41 approaches each other and sandwiches the convex portion 11 of the material plate 10. In this state, a direct current is passed so that the convex portion 11 becomes a cathode and the stamp 61 becomes an anode.

Here, as the plating treatment solution, for example, a cyan gold potassium solution is used, the gold concentration in the plating solution is set to 10 to 30 g / L, and the current density is set to 0.75 to 1.5 A / dm ² . The condition is strike plating. As a result, electrolysis of water occurs in the electrolytic system composed of the flat plate 42, the plating solution, and the material plate 10, and hydrogen is generated on the surface of the convex portion 11 serving as the cathode. At that time, hydrogen ions come into contact with the projections 11 to reduce the passive film 12, and gold plating K is deposited at the place where the passive film 12 is removed. Here, the thickness of the gold plating K applied to the material plate 10 is not particularly limited. However, when the amount of gold used is reduced and economy is taken into consideration, the thickness is set to about 20 to 100 nm. In addition, the water washing process and the drying process which wash away a plating solution can be provided after a gold plating process.

  Next, FIG. 4 and FIG. 5 are diagrams showing another embodiment of the present invention. The plating apparatus B of this embodiment is different from the above embodiment in that a roller 61 is used for the gold plating stage 60. As shown in FIG. 5B, the roller 61 is schematically configured by providing a porous material 63 on the outer periphery of a roll 62 made of a conductive material and fixing a rotating shaft 64 at the center of the roll 62. .

  As the material of the roll 62, carbon, a Ti—Pt alloy, a Ti—Au alloy, a material in which Ir 2 O 3 is dispersed in Ti, or the like is used. As the material of the porous material 63, cloth, sponge, rubber or the like is used, and as the material of the sponge, urethane or polyvinyl alcohol (PVA) is used. In addition, means (not shown) for supplying a plating solution to the porous material 63 is provided. The roller 61 sandwiches the convex portion 11 of the material plate 10, and in this state, a direct current is passed so that the convex portion 11 becomes a cathode and the roller 61 becomes an anode.

  Here, the material plate 10 can also carry and process all the stages of the plating apparatus B in a horizontal state. However, when gold plating is performed in a horizontal state, a plating solution is accumulated on the upper surface of the material plate 10. There is a concern that the quality of the gold plating on the bottom surface varies. However, when gold plating is performed only on the convex portion 11 on one side of the material plate 10, there is no such concern.

  Therefore, before the material plate 10 is transported to the gold plating stage 70, the material plate 10 can be twisted by 90 ° and transported vertically. FIG. 5A shows a state in which the material plate 10 is placed vertically and gold plating is performed. As shown in this figure, the roller 61 sandwiches the convex portion 11 of the material plate 10, and in this state, a direct current is passed so that the convex portion 11 becomes a cathode and the roller 61 becomes an anode. Also in the embodiment, gold plating can be performed with the material plate 10 placed vertically.

A stainless steel plate made of SUS304 having a thickness of 0.1 mm was press-molded to obtain a material plate having a rectangular shape in plan view and a cross-sectional uneven shape (corrugated plate shape) as shown in FIG. Each treatment of degreasing, washing with water and gold plating was performed on the material plate according to the flow shown in FIG. In gold plating, while supplying a cyanogen gold potassium solution having a gold concentration of 10 g / L to the porous material 43 of the stamp 41 in FIG. 3, a direct current having a current density of 1.5 A / dm ² is applied to the material plate. The plate 42 was allowed to flow for 10 minutes.

  When the material plate after gold plating was investigated, it was confirmed that almost no plating was observed in the portions other than the convex portions of the raw material plate, and that the gold plating was selectively formed on the convex portions.

  The present invention is very promising as a method for manufacturing an inexpensive fuel cell because the step of removing the passive film can be omitted and the conductive metal can be plated only on the portion where the conductivity of the separator is required.

DESCRIPTION OF SYMBOLS 10 Material board 11 Convex part 12 Passive film 43, 63 Porous material (plating solution holding material)

Claims (3)

A press forming step of forming a metal material plate with a concavo-convex section, and
A plating step of plating a conductive metal only on the convex portion of the material plate formed in the concavo-convex shape of the cross section,
In the plating step, a plating solution holding material holding a plating solution containing ions of the conductive metal is brought into contact with only the convex portion, and a predetermined current density (average) is provided between the plating solution holding material and the material plate. performed by energizing with the exception of current density 5~26A / dm ^2), and, while reducing the passive film formed on the surface of the material plate to generate hydrogen by hydrogen at the surface of the blank A method for producing a fuel cell separator, comprising plating the conductive metal on the material plate. A press forming step of forming a metal material plate with a concavo-convex section, and
A plating step of plating a conductive metal only on the convex portion of the material plate formed in the concavo-convex shape of the cross section,
The plating step is performed by bringing a plating solution holding material holding a plating solution containing ions of the conductive metal into contact with only the convex portion and energizing between the plating solution holding material and the material plate, And the manufacturing method of the separator for fuel cells which generates the hydrogen on the surface of the said raw material plate, and plating the said conductive metal on the said raw material plate, reducing the passive film formed on the surface of the said raw material plate by this hydrogen Because
The plating solution holding material includes a pair of stamps provided with a porous material on one side of a flat plate made of a conductive material, impregnated with plating solution on one or both of the porous materials of the stamp, A method for manufacturing a fuel cell separator, wherein the material plate on which the substrate is formed is sandwiched between stamps, and the flat plate and the material plate are energized in this state. A press forming step of forming a metal material plate with a concavo-convex section, and
A plating step of plating a conductive metal only on the convex portion of the material plate formed in the concavo-convex shape of the cross section,
The plating step is performed by bringing a plating solution holding material holding a plating solution containing ions of the conductive metal into contact with only the convex portion and energizing between the plating solution holding material and the material plate, And the manufacturing method of the separator for fuel cells which generates the hydrogen on the surface of the said raw material plate, and plating the said conductive metal on the said raw material plate, reducing the passive film formed on the surface of the said raw material plate by this hydrogen Because
The plating solution holding material includes a pair of rollers in which a surface of a roll made of a conductive material is covered with a porous material. One or both of the rollers are impregnated with the plating solution, and uneven by press molding. A method for producing a fuel cell separator, wherein the roller is rotated while energizing the roll and the material plate in this state.

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