JP2002050366A - Solid polymer fuel cell metal separator and fuel cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer electrolyte fuel cell metal separator that has a small surface resistance and an excellent acid resistance, and a fuel cell using the same. SOLUTION: This is a solid polymer fuel cell metal separator in which the surface of the metal substrate is coated with a resin composite comprised of conducting particles containing conducting ceramics particles, or conducting particles containing conducting ceramics particles and carbon particles, and a resin, and a fuel cell using the separator is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel separator for a solid polymer electrolyte fuel cell, a solid polymer electrolyte fuel cell using the same, and a conductive paint.

[0002]

2. Description of the Related Art There are known fuel cells of a polymer electrolyte type, a molten carbonate type, a phosphoric acid type, a solid oxide type and the like based on an electrolyte used. The polymer electrolyte fuel cell has higher current density, longer life, less degradation due to start / stop, lower operating temperature (about 80 ° C), lower load operation, and higher precision than other fuel cells. Since the differential pressure control has such advantages as being unnecessary, a wide range of applications such as automobiles, stationary and home power supplies are expected.

A single cell of a polymer electrolyte fuel cell uses a polymer film having a proton (H ⁺ ) conductivity of about 100 μm and having a thickness of several tens of μm on both sides of the membrane. An electrode such as a carbon sheet carrying a Pt alloy catalyst is baked, and a gas flow path for supplying hydrogen (H ₂ ) to one electrode and air (oxygen (O ₂ )) to the other electrode is formed, and an electrolyte membrane and an electrode are formed. Is constituted by a housing (separator) for fixedly holding. A battery stack is constructed by stacking a plurality of the single cells. The electrode reaction is as follows: hydrogen electrode (anode): H ₂ → 2H ⁺ + 2e ⁻ , oxygen electrode (cathode): 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O. Since the H ⁺ generated at the anode is led to the cathode through the polymer electrolyte membrane (ion exchange membrane), the electrolyte membrane is maintained in a wet state. Since the electrolyte membrane has a sulfone group and is maintained in a wet state, the separator fixed with the porous thin carbon sheet interposed therebetween is exposed to strong acidity.

Conventionally, a functional material has been used as a separator material, and graphite has been used for 19 (1999) 15. Japanese Patent Application Laid-Open No. 11-345618 discloses a metal having a surface coated with a conductive carbon paint, Ag powder, Ni powder. The use of a substrate has been shown.

[0005]

In a fuel cell, since single cells are stacked, electric power is taken out through a large number of separators, and a reduction in the resistivity of the separator material is a major problem in terms of power generation efficiency. Further, since it is used in a humid and strongly acidic atmosphere, acid resistance is also required. Further, it is premised that the separator has high strength and low cost for practical use of the separator. The graphite separator according to the prior art is almost satisfied in terms of resistivity and acid resistance, but not only is the material itself expensive, but also the processing cost is high because the fuel gas flow path is manufactured by cutting. . In addition, graphite is brittle, so it is vulnerable to mechanical shock and vibration and lacks reliability when used as a power source for automobiles. Another conventional metal separator having a surface coated with a conductive carbon paint has been made to solve these problems, and is inexpensive and superior in acid resistance and strength as compared to graphite. However, the resistivity of the carbon material is on the order of 10 ^-3 Ωcm, which is 2-3 times smaller than that of metal.
Because of the order of magnitude, a sufficiently low sheet resistance (resistance per unit area) cannot be obtained with a metal separator coated with a paint using carbon powder as a conductive filler. For example, JP-A-11-
The sheet resistance of a metal separator coated with a paint using carbon powder as a conductive filler as disclosed in JP-A-345618 is 17-6.
8 mΩcm ² . The sheet resistance of the graphite separator material is 0.
It is about 50 to 220 times larger than 3 mΩcm ² . If the sheet resistance is large, a large amount of Joule heat is generated, which lowers the power generation efficiency of the fuel cell, which is not preferable.

An object of the present invention is to provide a metal separator for a polymer electrolyte fuel cell having a small sheet resistance and excellent acid resistance, a fuel cell using the same, and a conductive paint.

According to the present invention, as a result of examining the type and resin of conductive particles of a coating material applied to a metal substrate, it has been found that metal silicide, carbide, or nitride-based conductive ceramic particles or conductive particles are used. The present inventors have found that a metal separator coated with a resin in which conductive particles containing conductive ceramic particles and carbon particles are dispersed is excellent in terms of resistivity, acid resistance, and strength.

According to the present invention, the surface of a metal substrate is coated with a resin composition having conductive particles and a resin. The resin composition has a sheet resistance of 0.1 to 6.0 mΩcm ² ,
0 ° C., -1 V to 1.5 in 0.5 mol% H ₂ SO ₄ solution
The current density at the time of cleaning to V 10 ^{Tsu 4} A / cm ² or less, or 80 ° C., it is preferred that 1 mol% H ₂ SO ₄ solution for 168 hours after dipping weight loss in the 0.1% or less .

[0008] The present invention resides in a conductive paint comprising conductive resin containing conductive ceramic particles and carbon particles, and a resin.

The conductive ceramic particles include metal borides, silicides, nitrides, and carbides, and have a resistivity of about 1
0 ^-5 to 10 ^-6 Ωcm. The resistivity of graphite is 10 ^-3 Ωc
Since it is two to three orders of magnitude smaller than the order of m, a sufficiently low sheet resistance can be achieved with a metal separator coated with a resin in which conductive ceramic particles are dispersed. But,
In terms of acid resistance, a resin in which a metal boride is dispersed is small, and a metal silicide (FeSi ₂ , MoSi ₂ , ZrS
Experiments have shown that a resin in which i ₂ , TiSi), metal carbide (WC), and metal nitride (TiN) are dispersed is excellent. WC is the best in terms of price. One kind of the above-mentioned conductive ceramics may be dispersed in the resin, but two or more kinds may be dispersed and used.

Examples of the resin include thermoplastic resins such as polystyrene, polyamide, methyl methacrylate, ABS resin, and vinylidene fluoride, and thermosetting resins such as phenol resin, urea resin, melamine resin, furan resin, and epoxy resin. Among these resins, thermosetting resins such as furan resins and epoxy resins and fluorinated resins that can withstand the temperature of around 80 ° C., which is the operating environment of the solid polymer electrolyte fuel cell, and the acidic and steam environment conditions It was a fluororesin such as vinylidene. Vinylidene fluoride was the best in terms of acid resistance, but the thermosetting resin was better in terms of adhesion to a metal substrate.

Metal silicides (FeSi ₂ , MoSi ₂ , Z
rSi ₂ , TiSi), metal carbide (WC), and metal nitride (TiN) in the resin in a mixing ratio of 20 to 50.
vol% is good. At 20 vol% or less, the conductivity is poor,
If it is 50 vol% or more, the conductivity is good, but the porosity of the film becomes high, so that the acid resistance deteriorates. Further, the adhesion of the film is also reduced. The average particle size of the conductive ceramic is 1-10μ
m is preferred. Even if the particle diameter is 1 μm or less, there is no problem in terms of conductivity, but the price of the raw material powder becomes expensive. If it is 10 μm or more, the conductivity will be poor. It is preferable to use a mixture of powders having two or more kinds of average particle diameters because the porosity can be reduced.

The thickness of the resin layer in which the conductive ceramic particles or the conductive ceramic particles and the carbon particles are dispersed is 30.
It is preferably from 200 to 200 μm. When the film thickness is 30 μm or less, conductivity is improved, but reliability of acid resistance is reduced. When the film thickness is 200 μm or more, the reliability of acid resistance is improved, but the conductivity is unfavorably deteriorated. In addition, since more conductive ceramics are used, the cost is higher.

As the carbon particles, graphite powder and carbon black are used, and preferably 30 vol% or less.

The sheet resistance of the resin layer in which the conductive ceramic particles prepared under the above favorable conditions were dispersed on a stainless steel substrate was 0.12 to 5.9 mΩcm ² . The resistivity of the resin layer is preferably as small as possible. However, if the sheet resistance is 0.12 mΩcm ² or less, the conductive layer becomes thin or the conductive filler is increased, so that the porosity increases and the reliability of acid resistance deteriorates. Even when carbon is used as the conductive filler, a sheet resistance of about 10 mΩcm ² can be achieved by increasing the content, so that
At 5.9 mΩcm ² or more, the significant difference from the case of using carbon becomes small.

The metal substrate is not particularly limited, but SUS304 and SUS316 having acid resistance in terms of reliability.
And the like are preferred.

[0016]

[Embodiment 1] FIG. 1 is a schematic sectional view showing one structure of a fuel cell using a metal separator coated with a conductive ceramic paint of the present invention. There are electrodes 2a and 2b supporting Pt on carbon mesh with the Nafion-based solid polymer electrolyte membrane 1 interposed therebetween. Electrode 2a,
2 b is pressed against the electrolyte membrane 1. Electrolyte membrane 1 and electrode 2
a and 2b are sandwiched between metal separators 3 coated with a conductive ceramic paint. Fuel gas and oxidizing gas (air) mainly composed of H2 are respectively supplied to the gas passage grooves 3a and 3b of the metal separator 3. The heat generated by the power generation is cooled by water supplied to the water flow paths 4a and 4b and is maintained at about 80 ° C. Gas is sealing material 5a, 5
b.

In the metal separator 3 coated with the conductive ceramic paint, hydrogen dissociates on the surface of the catalyst at the hydrogen electrode (anode) to generate protons (H ⁺ ), so that the electrode contact portion is acidic. At the oxygen (air) electrode, protons (H ⁺ ) and oxygen that have passed through the electrolyte react with each other on the catalyst to generate water. Therefore, the electrode contact portion is under a steam atmosphere and is acidic. The metal separator according to the present invention, which is coated with a resin in which metal silicide, carbide, or nitride-based conductive ceramic particles are dispersed, can sufficiently withstand this environment.

Example 2 Borides (W ₂ B ₅ , TiB ₂ , TaB), which are conductive ceramics having an average particle diameter of 3 to 10 μm, were added to 5 g of a liquid oily shell epoxy resin (Ep806) as a conductive filler. ₂ , ZrB ₂ ), carbide (W
C, TiC, TaC, ZrC), nitride (TiN, Ta)
N, ZrN), silicides (FeSi ₂ , MoSi ₂ , ZrS)
45 vol% each of i ₂ , TiSi) powder and scale graphite made of Nippon Graphite (CSPE, average particle diameter 4.5 μm) and mesocarbon made by Osaka Gas (average diameter 10 μm) for comparison.
And kneaded using an agate bowl to prepare a paint. The size of this paint polished on the surface is 20 × 10
A test piece made of SS400 having a thickness of 4 mm and a thickness of 4 mm was substantially uniformly applied to one surface by a casting method, and heat-treated at 150 ° C. for 7 hours under vacuum. The obtained test piece was sandwiched between an indium plate and a silver plate, and the sheet resistance including the carbon steel substrate of the metal separator coated with the conductive ceramic paint was measured using a four-terminal method. Table 1 shows the measurement results.

[0019]

[Table 1]

As can be seen from Table 1, the metal separator of the present invention coated with a paint using conductive ceramic as a filler is almost the same as the metal separator coated with a paint using graphite or a carbon conductive filler of the comparative example. 1 with the same film thickness
~ 2 digits surface resistance can be reduced. The sheet resistance of the graphite separator is 0.3 mΩcm ^2, which is equal to or several times as large as that of the graphite separator and excellent in conductivity.

Example 3 Using the sample and the paint obtained in Example 2, acid resistance was evaluated by the following two methods. One is to harden a portion of the sample obtained in Example 2 where the conductive paint is not applied with an araldite resin,
Mol% H ₂ SO ₄ solution immersed in, a voltage from -1 to +1.
The current density flowing while sweeping slowly to 5 V was measured. On the other hand, the coating material obtained in Example 2 was applied to the entire surface of a carbon steel plate having a size of 20 × 60 mm and a thickness of 1.2 mm by using a casting method, and was applied at 80 ° C. and 1 mol% H. _It was immersed in a ₂ SO ₄ solution, and the weight loss rate was measured. Table 2 shows the test results.

[0022]

[Table 2]

According to Table 3, nitride: TiN, carbide: W
C, silicide: MoSi ₂ , FeSi ₂ , TiSi ₂ , Zr
It can be said that Si ₂ has excellent acid resistance.

[Example 4] MoSi ₂ , FeSi ₂ , WC, which was found to have excellent acid resistance in Example 3, and graphite as a comparative example were added to a liquid oilified shell epoxy resin (Ep806). The mixture was mixed at the ratio described above to prepare a coating material, applied to a carbon steel plate, and evaluated for sheet resistance and acid resistance, thereby examining an optimum mixing ratio. The method for preparing the conductive paint, the coating method, the baking method, and the evaluation method for the sheet resistance were performed in accordance with Example 2. The thickness of the resin layer was about 100 μm.

FIG. 2 is a diagram showing the relationship between the sheet resistance and the amount of conductive ceramic particles added. As shown in FIG. 2, the conductive ceramic has lower sheet resistance than graphite. The sheet resistance does not depend on the type of conductive ceramics,
From 20vol% to 20vol%
From 30% to about 30%
It is almost constant at% or more. The minimum sheet resistance varies slightly depending on the type of conductive ceramics, but is several mΩcm ²
It is as follows. It is considered that the reason why the sheet resistance rapidly decreases from 10 to 20 vol% is that the particles are in contact with each other to form a conductive path. If the mixing ratio of the conductive ceramics is 50 vol% or less, the viscosity of the paint becomes small and the paint becomes easy to apply. Further, since the porosity is small, the reliability of acid resistance also increases. From the above, it can be said that the mixing ratio of the conductive ceramic is preferably 20 to 50 vol%.

Example 5 The average particle diameter of MoSi ₂ , FeSi ₂ , and WC, which was found to have excellent acid resistance in Example 3, was changed by changing the liquid oilified shell epoxy resin (Ep806). A paint was prepared, applied to a carbon steel sheet, and evaluated for sheet resistance and acid resistance to determine the optimum particle size. The mixing ratio of conductive ceramics is 30vol
% Was constant, and the film thickness was about 100 μm. The method for preparing the conductive paint, the coating method, the baking method, and the evaluation method for the sheet resistance were performed in accordance with Example 2.

FIG. 3 is a diagram showing the relationship between the sheet resistance and the average particle size of the conductive ceramic particles. As shown in FIG. 3, the sheet resistance does not depend much on the type of the conductive ceramic, and the sheet resistance tends to decrease as the average particle diameter becomes smaller. If the average particle diameter is 10 μm or less, the sheet resistance is in a practical range, and therefore it can be said that the average particle diameter is 1 to 10 μm.

[Example 6] MoSi ₂ , FeSi ₂ , and WC powders, which were found to have excellent acid resistance in Example 3, were added to 30 vol% of 5 g of a liquid epoxy resin (Ep806) made of oiled shell. And then kneaded using an agate bowl to prepare a coating. This coating material was appropriately diluted with a solvent, applied to a carbon steel sheet at various thicknesses using a dipping method or a casting method, and baked to prepare a sample. The paint was applied to one surface of the sample for measuring sheet resistance and to the entire surface of the sample for acid resistance evaluation. The optimum film thickness was examined by evaluating the sheet resistance and acid resistance of the obtained sample. The measurement of the sheet resistance was performed according to Example 2, and the evaluation of the acid resistance was performed according to the measurement of the weight loss rate of Example 3.

Table 3 shows the relationship between acid resistance and film thickness due to weight loss after immersion in a 1 mol% H ₂ SO ₄ solution at 80 ° C. for 168 hours, and Table 4 shows the relationship between sheet resistance and film thickness. It is shown.

[0030]

[Table 3]

[0031]

[Table 4]

As evident from Table 3, the film thickness is preferably 30 μm or more for acid resistance, and as evident from Table 4, MoSi ₂ as conductive ceramic particles has a sheet resistance of 10 mΩcm ² or less. The thickness is preferably 200 μm or less. Other conductive ceramic particles can have a thickness up to about 500 μm.

Example 7 In order to investigate the effect of the type of resin on the properties of the conductive coating film, commercially available thermoplastic resins such as polystyrene, polyamide, methyl methacrylate, and vinylidene fluoride were used, and phenol was used as the thermosetting resin. resin,
Urea resin, melamine resin, furan resin, epoxy resin,
A coating material was prepared using a commercially available diallyl phthalate resin and WC having an average particle diameter of 3 μm as a conductive filler.
WC was added to 30 vol% with respect to the resin amount (3 g), and the mixture was kneaded for several minutes in an agate bowl to prepare a paint. At this time, the viscosity was adjusted by adding an appropriate amount of a solvent as needed.

The obtained paint was applied to an SS400 plate having a size of 10 × 40 × 1 mm by a dipping method so as to have a film thickness of about 100 μm. In the case of thermosetting resin,
The polymer was heated at a temperature of about 50 ° C. for several hours for polymerization. In the case of a thermoplastic resin, the conductive film was formed by heating under vacuum to evaporate the solvent. The obtained sample was heated at 80 ° C. and H ₂ SO ₄ concentration 1
An acid resistance test was performed by exposing it to a mol% and 1 atmosphere environment. Evaluation of acid resistance was performed by measuring the sheet resistance after immersion for 7 days.

Table 5 shows the results of the acid resistance test of the resin. From Table 5, it is clear that thermoplastic vinylidene fluoride, thermosetting furan resin, and epoxy resin have excellent acid resistance.

[0036]

[Table 5]

Example 8 A single fuel cell having the schematic structure shown in Example 1 was experimentally manufactured, and the assembly of the separator according to the present invention in a battery was evaluated. As a separator constituting a polymer electrolyte fuel cell, stainless steel (S
US316) 150 mm × 150 mm × 2.5 mm thick
1mm width and 1m depth by machining in the area of 00mm
m gas flow paths and gas introduction holes were prepared. 70 vol% of epoxy resin,
WC (average particle size 2.5 μm) 25 vol% paint is applied based on the spray method, and the film thickness is about 100 μm
Was formed.

A single cell of a solid polymer fuel cell was manufactured by combining the obtained two separators with a Gore membrane with a gas diffusion electrode interposed therebetween so that the gas flow became a cross flow. This battery was used at 80 ° C., a fuel utilization rate of 70%, an oxygen utilization rate of 40%, and a charge density of 0.5 A / cm ² .
A continuous power generation test for hours was performed. After the test, the battery was disassembled and the change in the sheet resistance and the corrosion state of the separator were visually observed and observed by an optical microscope. As a result, there was almost no change in the sheet resistance and no corrosion was observed. From the above, it is determined that the separator according to the present invention can be used for a fuel cell.

EXAMPLE 9 5 g of WC having an average particle size of 3 μm was added to 5 g of an epoxy resin (Ep806) made by Yuka Shell.
Carbon powders having 0, 15, 20, 25 vol% and an average particle diameter of 6 μm were added to make 25, 20, 15, 10, 5 vol%, and a total of 30 vol% was added, and kneaded using an agate bowl to prepare a paint. did. This coating material was applied on a carbon steel sheet having a size of 10 × 15 × 4 mmt and 10 × 40 × 2 mmt using a casting method with a film thickness of about 100 μm.
The sample was prepared by baking at 0 ° C. for 6 hours.

Using a sample having a size of 10 × 15 × 4 μmt
The sheet resistance and the polarization characteristics are 10 × 40 × 2 mmt.
80 ° C, 1 mol% H using sample_TwoSO_FourAcid resistance test in
Was carried out by As for the sheet resistance, the mixing ratio of WC is 5 to 25 vo.
46.5 to 0.58 mΩcm over the entire range of 1%^TwoAnd small
In addition, the polarization characteristics are 10 in the range of voltage -1 to 1.5V.
^{Tsu Four}A / cm^Two The following was excellent. In addition, 7 days of H_TwoSO
_FourExcellent in weight reduction rate of 0.05% or less even in immersion test in air
I was From the above, conductive ceramic particles and charcoal
A resin composition having elementary particles and a resin is applied to the surface of a metal substrate.
Excellent separator can be obtained by coating
it is obvious.

[0041]

According to the present invention, a metal separator for a polymer electrolyte fuel cell having low sheet resistance and excellent acid resistance can be obtained, and a solid polymer electrolyte fuel cell having high performance and high reliability can be obtained. Can be

[Brief description of the drawings]

FIG. 1 is a sectional view of a metal separator for a polymer electrolyte fuel cell according to the present invention.

FIG. 2 is a diagram showing the relationship between sheet resistance and the amount of conductive ceramic particles added.

FIG. 3 is a diagram showing a relationship between a sheet resistance and an average particle size of conductive ceramic particles.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Degradation film, 2a, 2b ... Electrode, 3 ... Metal separator coated with conductive ceramic paint, 3a, 3b ... Gas flow channel,
4a, 4b: cooling water passage grooves, 5a, 5b: sealing members.

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[Procedure amendment]

[Submission date] December 5, 2000 (200.12.
5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

The present invention relates to relates to a novel solid polymer electrolyte fuel cell separator and a solid polymer electrolyte fuel cells using the same.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

According to the present invention, the surface of a metal substrate is coated with a resin composition having conductive particles and a resin. The resin composition has a sheet resistance of 0.1 to 6.0 mΩcm ² ,
0 ° C., -1 V to 1.5 in 0.5 mol% H ₂ SO ₄ solution
The current density at the time of cleaning up V is 10 ^{- 4} A / cm ² or less, or 80 ° C., it is preferred that 1 mol% H ₂ SO ₄ solution for 168 hours after dipping weight loss in the 0.1% or less .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Deleted

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

Using a sample having a size of 10 × 15 × 4 μmt
The sheet resistance and the polarization characteristics are 10 × 40 × 2 mmt.
80 ° C, 1 mol% H using sample_TwoSO_FourAcid resistance test in
Was carried out by As for the sheet resistance, the mixing ratio of WC is 5 to 25 vo.
46.5 to 0.58 mΩcm over the entire range of 1%^TwoAnd small
In addition, the polarization characteristics are 10 in the range of voltage -1 to 1.5V.
^{- Four}A / cm^Two The following was excellent. In addition, 7 days of H_TwoSO
_FourExcellent in weight reduction rate of 0.05% or less even in immersion test in air
I was From the above, conductive ceramic particles and charcoal
A resin composition having elementary particles and a resin is applied to the surface of a metal substrate.
Excellent separator can be obtained by coating
it is obvious.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanori Yoshikawa 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Hirofumi Yamauchi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi, Ltd.Hitachi Research Laboratory (72) Inventor Kazuhisa Higashiyama 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory (72) Inventor Yuichi Kamo Hitachi, Ibaraki Prefecture 7-1-1, Omikacho Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shuichi Ohara 7-1-1, Omikamachi, Hitachi, Ibaraki F-term Hitachi Research Laboratory, F-term (reference) 5G301 CA01 CA03 CA06 CD02 5H026 AA06 CC03 EE02 EE05 EE11

Claims (11)

[Claims] 1. A metal separator for a polymer electrolyte fuel cell, wherein a surface of a metal substrate is coated with a resin composition having conductive particles containing conductive ceramics and a resin. 2. A metal separator for a polymer electrolyte fuel cell, wherein a surface of a metal substrate is coated with a resin composition having a resin and conductive particles including conductive ceramic particles and carbon particles. 3. The method of claim 1 or 2, wherein the resin composition, 20 ° C., 0.5 mol% H ₂ SO ₄ current density when swept from over 1V to 1.5V in a solution of 10 ^{Tsu 4} A / cm ²
A metal separator for a polymer electrolyte fuel cell, wherein a weight reduction rate after immersion in a 1 mol% H ₂ SO ₄ solution at 80 ° C. for 168 hours is 0.1% by weight or less. 4. The metal separator for a polymer electrolyte fuel cell according to claim 1, wherein said conductive ceramic is made of at least one of a metal silicide, a metal carbide and a metal nitride. . 5. The metal separator for a polymer electrolyte fuel cell according to claim 1, wherein the conductive particles are contained in the resin composition in an amount of 20 to 50% by volume. 6. The metal separator for a polymer electrolyte fuel cell according to claim 1, wherein the conductive particles have an average particle size of 1 to 10 μm. 7. The metal separator for a polymer electrolyte fuel cell according to claim 1, wherein said resin composition layer has a thickness of 30 to 200 μm. 8. The metal separator for a polymer electrolyte fuel cell according to claim 1, wherein the resin composition layer has a sheet resistance of 0.12 to 5.9 mΩcm ² . 9. A metal separator for a polymer electrolyte fuel cell according to claim 1, wherein said resin is one of a furan resin, an epoxy resin and a vinylidene fluoride resin. 10. A solid polymer fuel cell comprising a fuel cell having a solid polymer electrolyte membrane, electrodes provided on both sides of the electrolyte membrane, and separators disposed on each of the electrodes. In the separator, claims 1 to 1
A polymer electrolyte fuel cell comprising the separator according to any one of claims 9 to 13. 11. A conductive paint comprising conductive resin containing conductive ceramic particles and carbon particles and a resin.