JP4577040B2 - Manufacturing method of fuel cell separator - Google Patents

Description

The present invention relates to a process for the production of separators for use in fuel cells.

  The fuel cell separator is installed between adjacent single cells in a fuel cell configured by stacking a plurality of single cells. The separator has an uneven shape on the surface, and a fuel gas flow path or an air flow path is formed between the uneven shape and an adjacent member.

  Metal separators (metal separators) are required to have sufficient corrosion resistance and conductivity. Therefore, as a metal separator, for example, a metal separator in which a noble metal layer is formed on the surface of a metal material such as stainless steel or aluminum and a carbon coating layer is further formed on the noble metal layer is provided (Patent Document 1). And 2). These metal separators are excellent in corrosion resistance and conductivity.

JP 2002-63914 A JP 2001-307747 A

  The metal separators of Patent Documents 1 and 2 are excellent in corrosion resistance and conductivity due to the presence of the metal layer and the carbon coating layer. However, today's separators are required to have a sufficient thickness (particularly, a carbon coating layer having a uniform thickness) as well as ensuring sufficient corrosion resistance and conductivity. When the film thickness of the carbon coating layer becomes uniform, the fuel gas flow path or air flow path of the metal separator is reliably secured, and the fuel gas and air are reliably supplied to the entire fuel electrode and air electrode of the single cell, respectively. It becomes easy. In particular, there is a demand for further miniaturization of fuel cells today, and therefore a technology for forming a carbon coating film uniformly on the surface of the groove-shaped uneven portion of the groove-shaped uneven portion is desired. It is rare.

The present invention provides a separator base, a noble metal coating formed on the separator base, and a carbon coating formed by applying a carbon paint on the noble metal coating as means for solving the above-mentioned problems. The carbon coating film is formed by spraying a carbon paint composed of particles of 60 μm or less onto the noble metal film and volatilizing the solvent without flowing. The manufacturing method of the separator for fuel cells characterized by the above-mentioned is provided.

  In the fuel cell separator manufacturing method, the carbon paint preferably contains graphite, carbon black, styrene-butadiene rubber, and xylene.

According to the present invention, it is possible to provide a method for producing separators for fuel cells to form a carbon coating film having a uniform film thickness on the surface.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic view of a fuel cell separator 1 according to this embodiment. The fuel cell separator 1 has a gas supply path 6 (fuel gas supply path or air supply path) for supplying fuel gas or air on the front and back surfaces thereof. These gas supply paths 6 are composed of a plurality of grooves formed in the longitudinal direction of the fuel cell separator 1. The cross section of these gas supply paths 6 has an uneven shape as shown in FIG. The gas supply path only needs to be able to supply fuel gas or air to the electrode of the single cell, and the cross-sectional shape, the length, width, and depth of the groove are appropriately set. The cross-sectional shape of another gas supply path is shown in FIG.

  The fuel cell separator 1 includes a separator substrate 2, a noble metal coating 3 formed on the separator substrate 2, and a carbon coating 5 formed on the noble metal coating 3.

  As the separator base material 2, a material excellent in strength, conductivity, and moldability is used. As this separator base material, metal materials, such as aluminum and stainless steel, are used, for example. As the stainless steel, it is preferable to use an austenitic stainless steel having high corrosion resistance. For example, a stainless steel plate can be mechanically pressed to obtain a separator substrate 2 having a predetermined uneven shape.

  The noble metal used for the noble metal coating 3 is gold, silver or the like. The noble metal coating 3 is formed on the separator substrate 2 by a method such as a dry coating method or a wet coating method (plating or the like). The noble metal coating 3 is applied over the entire surface of the separator substrate 2. In addition, before forming the noble metal coating 3, a surface treatment may be performed on the separator substrate 2 in advance, or an underlayer may be provided.

  The carbon coating 5 is formed by applying a carbon coating 4 containing graphite and carbon black on the noble metal coating 3. Examples of the graphite used for the carbon coating 4 include artificial graphite, scaly graphite, scaly graphite, and earthy graphite. These graphites can be used alone or in combination of two or more. The particle size of the graphite used is in the range of 1 μm to 150 μm, desirably in the range of 5 μm to 30 μm. Further, only graphite having a single particle size may be used, or two or more types of graphite having different particle sizes may be used in combination.

  As the carbon black, channel black, furnace black, acetylene black, ketjen black and the like can be used. These carbon blacks can also be used alone or in combination of two or more. The particle size of the carbon black used is in the range of 1 μm to 100 μm, desirably in the range of 10 μm to 30 μm. Only carbon black having a single particle size may be used, or two or more carbon blacks having different particle sizes may be used in combination.

  The mass ratio of graphite to carbon black contained in the carbon coating is desirably 1 or more, and more desirably 2 or more. In addition, you may use only graphite or carbon black for a carbon coating material, without using graphite and carbon black together.

  The carbon coating film 5 includes a resin binder for binding the graphite and carbon black. Examples of the resin binder include fluorine resin, acrylic resin, polyester resin, urethane resin, phenol resin, phenol epoxy resin, styrene-butadiene rubber, butyl rubber, ethylene-propylene rubber, fluorine rubber, nitrile rubber, and chloroprene rubber. I can do it. These resin binders can be used alone or in combination of two or more.

  Examples of the solvent used for the carbon paint include xylene (o-xylene, m-xylene, p-xylene), toluene, isopropyl alcohol, water, methyl ethyl ketone, and the like. These solvents can be used alone or in combination of two or more.

  The solid content (% by mass) with respect to the total mass of the carbon coating is 10% by mass to 30% by mass, preferably 15% by mass to 25% by mass. When solid content exceeds 30 mass%, it will become difficult to control the particle size of a carbon coating material to 60 micrometers or less. Further, when a carbon coating film is formed on the separator surface using the carbon coating material, there arises a problem that aggregated powder of the carbon coating material or bubbles are generated in the carbon coating film. On the other hand, when the solid content is less than 10% by mass, the fluidity of the coating is increased, and the coating thickness tends to vary. In particular, when the wall surface 7 of each gas supply path 6 has a gradient in the gas supply path 6 of the separator, as in the fuel cell separator 11 of the reference example shown in FIG. 4, for example, The carbon coating film 5 becomes thin, and the carbon coating film 5 between the bottom surface 8 and the wall surface 7 of the supply path 6 becomes thick. The solid content of the carbon paint 4 is graphite, carbon black, and a resin binder.

  The carbon coating 5 is obtained by applying a carbon coating 4 controlled to a particle size of 60 μm or less, a separator substrate 2 on which a noble metal coating 3 is formed (hereinafter, a separator substrate 2 on which a noble metal coating 3 is formed) It may be formed by spray coating on top. For spray coating, for example, it is desirable to use a spray gun 9 that sprays the paint in the form of a mist with air.

  When the particle size of the carbon coating material 4 is 60 μm or less, the flow of the carbon coating material 4 applied on the separator can be suppressed. In particular, even when the wall surface 7 of the gas supply path 6 has a gradient as shown in FIG. 3, the flow of the carbon coating material 4 on the separator substrate 2 can be prevented. On the other hand, when the particle diameter of the carbon coating material 4 exceeds 60 μm, it becomes difficult to suppress the flow of the carbon coating material.

  The particle size of the carbon paint 4 was measured using a laser type particle counter (Laser Analyzer, manufactured by Tohnichi Computer Applications Co., Ltd.).

  An example of forming the carbon coating film 5 on the separator substrate 2 using the spray gun 9 will be described below. FIG. 5 is an explanatory view showing a state in which the carbon paint 4 is applied on the separator base 2 using the spray gun 9. The carbon paint 4 stirred by the stirring device 21 in the predetermined tank 20 is supplied to the paint storage chamber 25 of the spray gun 9 through the paint supply line 24 including the pump 22 and the pressure regulator 23. The spray gun 9 is supplied with first air 26 for atomizing the carbon paint 4 and adjusting the particle diameter. Further, the second air 27 for controlling the application range of the carbon paint 4 is supplied. The carbon paint 4 in the paint storage chamber 25 is discharged from the discharge port 28, and the opening and closing of the discharge port 28 is controlled by a discharge port adjusting valve (not shown). The atomized carbon paint 4 discharged from the spray gun 9 adheres to the separator substrate 2. The carbon coating 4 adhered on the separator substrate 2 does not flow, but the solvent in the carbon coating 4 gradually evaporates to form a carbon coating film 5.

  For example, the carbon paint 4 is applied by traversing a plurality of spray guns 9 on the separator base material 2 arranged in parallel as shown in FIG. When the width of the gas supply path 6 (strip groove) on the separator substrate 2 is 1.2 mm and the groove depth is 0.6 mm, the pitch (arrow P in FIG. 6) for moving the spray gun 9 is 40 mm to The range is set to 70 mm.

  The method of applying the carbon paint 4 with the spray gun 9 is not limited to the method of applying the spray gun 9 across the separator substrate 2 as described above. For example, the carbon paint 4 is applied around the separators 2 arranged in a plurality. A method of installing a plurality of spray guns 9 may be used, and any method may be used as long as the carbon coating film 5 can be uniformly formed on the separator 2.

  The thickness (film thickness) of the carbon coating film 5 according to this embodiment is in the range of 35 μm to 75 μm. Further, the variation in the film thickness of the carbon coating film 5 is desirably a standard deviation σ = 4.00 or less. The standard deviation of the film thickness of the carbon coating film 5 in the present embodiment is obtained based on the film thickness data on the wall surface 7 (elevation surface) of the gas supply path 6 in particular. In obtaining this standard deviation, in this embodiment, an abnormal value (outlier) is not particularly excluded. When obtaining the standard deviation, it is obtained by measuring at least 30 film thicknesses of the wall surfaces 7 of the plurality of gas supply paths 6 in one separator 1.

  After the carbon coating film 5 is formed on one surface of the separator 2 as described above, the carbon coating film 5 is formed on the other surface of the separator 2 in the same manner.

  As the spray gun 9, for example, spray gun: T-AGHV 546FX (manufactured by Devilvis) is preferably used. The case where the carbon coating film 5 is formed using the spray gun 9 will be described below.

  Using a spray gun 9 (T-AGHV 546FX) in which the atomizing air pressure is set to 0.3 MPa, the pattern air pressure is set to 0.4 MPa, and the discharge amount is set to 150 (cc / min), FIG. The separator 2 shown was painted. The atomizing air pressure is the pressure of the first air 26 shown in FIG. 5, and the pattern air pressure is the pressure of the second air 27. Here, when the respective masses of graphite, carbon black, and styrene butadiene rubber are expressed as Wg, Wcb, and Ws, the carbon coating 4 at this time is composed of graphite, carbon black, and styrene butadiene rubber as solid components. What was prepared in the ratio was used. The carbon paint 4 had a solid content of 10 to 30% by mass. The viscosity of the carbon paint 4 was 0.4 Pa · s (4 poise).

  When painting with the spray gun 9, the moving speed of the spray gun 9 was set to 370 mm / min and moved on the separator 2 along the wavy line shown in FIG. 6. The pitch P at the time of painting was set to 50 mm. Further, the spray gun 9 was moved six times on the wavy line. After the carbon paint 4 was applied on the separator substrate 2, the solvent of the carbon paint 4 was volatilized.

  As shown in FIGS. 7 and 3, the film thickness measurement method in the present embodiment measured the film thickness of the wall surface 7 (elevation surface) and the bottom surface 8 of the gas supply path 6. A laser microscope (manufactured by Lasertec Corporation) was used for measuring the film thickness.

  As shown in FIG. 7, three gas supply paths 6a, 6b, and 6c were arbitrarily selected from the plurality of gas supply paths 6 of the separator 1. For example, in the gas supply path 6a, the thicknesses of the wall surfaces 7a to 7j were measured at 10 locations. Similarly, in the gas supply paths 6b and 6c, the thicknesses of the respective wall surfaces are measured at locations corresponding to the positions of the wall surfaces 7a to 7j of the gas supply path 6a, and the standard deviation is obtained based on the measurement results. It was. It was confirmed that the standard deviation σ = 3.98.

  As described above, according to the present embodiment, it is possible to manufacture a fuel cell separator in which a carbon coating film having a uniform film thickness is formed.

  According to the present invention, as shown in FIG. 3, even when the wall surface of the gas supply path of the fuel cell separator has a gradient, the fuel cell separator has a carbon coating film having a uniform film thickness. Can be provided.

It is the schematic of the separator for fuel cells which concerns on this embodiment. It is AA sectional drawing of the separator for fuel cells in FIG. It is a fragmentary sectional view of the separator for fuel cells of other embodiments. It is a fragmentary sectional view of the separator for fuel cells of the reference example whose film thickness of a carbon coat is non-uniform. It is the schematic of a mode that a separator base material is apply | coated with a spray gun. It is explanatory drawing of the method of the movement of a spray gun in the case of apply | coating with the spray gun on the separator base material arranged in multiple numbers. It is explanatory drawing showing an example of the film thickness measurement location in the case of calculating | requiring the standard deviation of the film thickness of the carbon coating film of the separator for fuel cells.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Fuel cell separator, 2 Separator base material, 3 Precious metal coating, 4 Carbon coating, 5 Carbon coating, 6 Gas supply path, 7 Wall surface (elevation) of gas supply path, 8 Bottom surface of gas supply path, 9 Spray gun .

Claims (2)

A separator substrate;
A noble metal coating formed on the separator substrate;
A fuel cell separator comprising: a carbon coating film formed by coating a carbon paint on the noble metal coating,
The carbon coating film is formed by spraying a carbon coating comprising particles of 60 μm or less onto the noble metal coating, and volatilizing the solvent without flowing, thereby producing a fuel cell separator. .   The carbon paint contains graphite, carbon black, styrene-butadiene rubber, and xylene, and the solid content in the carbon paint is in the range of 15 to 25% by mass with respect to the total mass of the carbon paint. The manufacturing method of the separator for fuel cells of Claim 1.

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