JP4516628B2 - Metal separator for fuel cell and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solid polymer type fuel cell metal separator used for portable devices such as mobile phones and personal computers, household fuel cells, fuel cell vehicles, and the like, and a method for producing the same.

  In a polymer electrolyte fuel cell, a solid polymer electrolyte membrane sandwiched between an anode electrode and a cathode electrode is used as a single cell, and a plurality of single cells are stacked via an electrode called a separator (or bipolar plate). Configured.

  This separator material for fuel cells has a low contact resistance (which means that a voltage drop occurs due to an interfacial phenomenon between the electrode and the separator surface), which is maintained for a long time during use as a separator. The characteristic that it is done is required. In this regard, conventionally, application of metal materials such as aluminum alloy, stainless steel, nickel alloy, and titanium alloy has been studied in consideration of workability and strength.

  Further, since the inside of the fuel cell is in an acidic corrosive atmosphere, the material used for the separator is also required to have acid resistance that maintains a low contact resistance for a long time even in an acidic atmosphere.

  Metals such as stainless steel and titanium alloys have been studied as separator materials for fuel cells because they exhibit good corrosion resistance by forming a passive film on the surface. However, since this passive film has a large contact resistance (electrical resistance), when a metal such as stainless steel or titanium alloy is used as it is as a fuel cell separator, the passive film is formed on the surface in an acidic atmosphere. Tends to deteriorate significantly.

For this reason, several techniques for suppressing the increase in contact resistance and maintaining conductivity are proposed.
For example, Patent Document 1 proposes a separator in which an Au plating layer of 10 to 60 nm is attached to the surface of a base material such as stainless steel or titanium.
Patent Document 2 proposes a separator in which an acid-resistant metal film is formed on a stainless steel substrate using Ta or the like, and a noble metal film is formed thereon.
Further, Patent Document 3 discloses a metal separator formed with a conductive thin film composed of an oxide film of the metal substrate itself, an outermost layer metal, a noble metal, or carbon, and a gap between the oxide film and the conductive thin film. There has been proposed a metal separator in which an intermediate layer of Ta, Zr, Nb or the like is formed to improve the adhesion (adhesion strength) of the metal.

JP-A-10-228914 JP 2001-93538 A JP 2004-185998 A

  However, metals such as stainless steel and titanium alloys that have been studied conventionally have a tendency to remarkably deteriorate conductivity because a passive film is formed on the surface in an acidic atmosphere as described above. Therefore, when used as a separator, even if the contact resistance at the beginning of use is low, such a low contact resistance state cannot be maintained for a long period of time, and the contact resistance increases over time, causing current loss. There was a problem that. Moreover, when corroded, there also existed problems, such as degrading an electrolyte membrane with the metal ion eluted from a material.

  Moreover, in the technique described in Patent Document 1, when exposed to a severe acidic atmosphere in the fuel cell, the Au plating layer is peeled off to increase the contact resistance of the base material, and the performance of the fuel cell is lowered. There was a fear.

  Further, in the technique described in Patent Document 2, Ta, Zr, and Nb used for the acid-resistant metal film are all refractory metals having a melting point exceeding 1800 ° C., and thus are formed using a normal sputtering method. Then, pinholes are formed in the acid-resistant metal film. Since a noble metal film such as Au formed on the acid-resistant metal film is formed while leaving the pinhole of the acid-resistant metal film, the metal of the base material may be eluted from the pinhole in an acidic atmosphere. It was. In addition, the acid-resistant metal film such as Ta and the noble metal film such as Au have poor adhesion so as to be easily peeled off even in a tape peeling test. When used as a fuel cell separator, the gas diffusion layer ( There was a risk that the precious metal film such as Au would peel off due to friction between the carbon cloth and the performance of the fuel cell.

  And in the technique described in patent document 3, when forming an intermediate | middle layer on an oxide film, since these adhesiveness was bad, there existed a possibility that a conductive thin film might peel off. Further, when an intermediate layer is formed using a high melting point metal such as Ta, Zr, or Nb between the oxide film and the conductive thin film, a pinhole may be formed in the intermediate layer as in Patent Document 2. There was also a risk that the metal substrate was eluted from here. Further, when the conductive thin film is a noble metal, there is a possibility that the adhesion is poor and peels off.

  This invention is made | formed in view of the said problem, and makes it a subject to provide the metal separator for fuel cells which is excellent in acid resistance, and has low contact resistance, and its manufacturing method.

In order to solve the above-mentioned problems, the metal separator for a fuel cell according to the present invention is manufactured using a metal base material having a flat surface or a concave gas flow path formed on at least a part of the surface. a metal separator for a fuel cell, on the surface of the metal substrate, Zr, Nb, consisting of any one non-noble metals selected from Ta, and the acid-resistant metal film of less than thickness of 5nm or more 100 nm, The acid-resistant metal film includes one or more noble metals selected from Au and Pt and one or more non-noble metals selected from Zr, Nb, and Ta, and the non-noble metals are contained in 5 to 65 atoms. % including Naru in a thickness possess a more conductive alloy film 2 nm, and the acid-resistant metal coating, in PVD method while heating the metal substrate than 50 ° C., a voltage below -50V By applying It has a configuration in which was deposited on top of the Shokumotozai.

Thus, the metal separator for a fuel cell according to the present invention, the surface of the metal substrate, Zr having excellent acid resistance, Nb, acid-resistant metal film made of any one of the non-noble metals selected from Ta Thus, the elution of the metal substrate can be prevented. In addition, the fuel cell metal separator is one or more selected from the above-described non-noble metals and Au and Pt that not only have excellent acid resistance but also do not form an oxide film in an acidic atmosphere on the acid resistant metal film. The contact resistance is reduced because the adhesion between the acid-resistant metal film and the conductive alloy film can be improved while having excellent acid resistance by further having a conductive alloy film comprising a noble metal. It becomes possible.

  In the fuel cell metal separator according to the present invention, the composition of the non-noble metal in the conductive alloy film is 5 to 65 atomic%, so that the adhesion between the acid-resistant metal film and the conductive alloy film is further increased. Therefore, the possibility that the conductive alloy film peels from the acid-resistant metal film due to friction or the like can be reduced, and the contact resistance can be further reduced.

  Since the metal separator for fuel cells according to the present invention has a film thickness of the acid-resistant metal film of 5 nm or more and less than 100 nm, it prevents the formation of pinholes and makes it difficult to expose the metal substrate. The elution of the material can be prevented. That is, more excellent acid resistance can be provided.

  Since the metal separator for a fuel cell according to the present invention has a thickness of the conductive alloy film of 2 nm or more, the contact resistance can be more reliably lowered while providing excellent acid resistance.

In the metal separator for a fuel cell according to the present invention, the metal base material is preferably any metal material selected from pure titanium, titanium alloy, stainless steel, pure aluminum, aluminum alloy, pure copper, and copper alloy. .
In this way, a fuel cell metal separator made of pure titanium, titanium alloy, stainless steel, pure aluminum, aluminum alloy, pure copper or copper alloy having low acid resistance while having excellent acid resistance can be obtained.

The method for producing a metal separator for a fuel cell according to the present invention comprises a metal separator for a fuel cell produced using a metal substrate having a flat surface or a concave gas channel formed on at least a part of the surface. the method of manufacturing, the surface of the metal substrate, by PVD method, Zr, Nb, consisting of any one non-noble metals selected from Ta, acid-resistant metal film of less than thickness of 5nm or more 100nm And one or more kinds of noble metals selected from Au and Pt and one or more kinds of non-noble metals selected from Zr, Nb and Ta by the PVD method on the acid-resistant metal film. And forming a conductive alloy film having a film thickness of 2 nm or more, comprising 5 to 65 atomic% of the non-noble metal, and forming the acid-resistant metal film, In the PVD method, While heating the serial metal substrate above 50 ° C., thereby forming a acid-resistant metal coating on the metal substrate by applying a voltage below -50 V.

  Thus, by applying voltage while heating the metal substrate in the step of forming the acid-resistant metal film, a dense acid-resistant metal film can be formed on the metal substrate. Elution can be prevented. In addition, while having excellent acid resistance by forming a conductive alloy film on the acid resistant metal film, the contact resistance was lowered by improving the adhesion between the acid resistant metal film and the conductive alloy film. A metal separator for a fuel cell can be manufactured.

  In the method for producing a metal separator for a fuel cell according to the present invention, the composition of the non-noble metal in the conductive alloy film is 5 to 65 atomic% in the step of forming the conductive alloy film. Since the adhesion between the film and the conductive alloy film can be further increased, the possibility that the conductive alloy film is peeled off from the acid-resistant metal film due to friction or the like can be reduced, and the contact resistance can be further reduced. Is possible. In addition, since the acid-resistant metal film is formed until the film thickness is 5 nm or more and less than 100 nm, pinhole formation can be prevented and the metal substrate can be made difficult to be exposed. The metal separator for fuel cells provided with can be manufactured.

  The method for producing a metal separator for a fuel cell according to the present invention has excellent acid resistance because the conductive alloy film is formed until the film thickness of the conductive alloy film is 2 nm or more in the step of forming the conductive alloy film. It is possible to manufacture a metal separator for a fuel cell having a lower contact resistance while having the properties.

  In the method for producing a metal separator for a fuel cell according to the present invention, the heating condition of the metal substrate in the step of forming the acid-resistant metal film is 50 ° C. or more, and the voltage application condition to the metal substrate is − ( Minus) Since it is 50 V or less, it is difficult to form pinholes in the acid-resistant metal film, a good acid-resistant metal film can be obtained, and a metal separator for a fuel cell that prevents metal elution from the metal substrate can be manufactured. it can.

In the method for producing a fuel cell metal separator according to the present invention, the PVD method is preferably an ion plating method or a sputtering method.
When the film forming process or the deposition process is performed using the ion plating method or the sputtering method in this way, particles that are positively ionized around the substrate by the generated plasma, that is, ionized gas (a part of the particles to be deposited or argon gas) Particles) can be present. In addition, due to the Coulomb force generated by applying a negative voltage to the substrate, the ionized particles collide with the substrate, and the kinetic energy of the ionized particles is given to the substrate as thermal energy. It is possible to activate the surface diffusion of the deposited particles, and to form a dense acid-resistant metal film.

In the method for producing a fuel cell metal separator according to the present invention, the metal base material is any metal material selected from pure titanium, titanium alloy, stainless steel, pure aluminum, aluminum alloy, pure copper, and copper alloy. Is preferred.
In this manner, a fuel cell metal separator made of pure titanium, titanium alloy, stainless steel, pure aluminum, aluminum alloy, pure copper or copper alloy with low acid resistance while having excellent acid resistance can be produced. .

The metal separator for a fuel cell of the present invention is excellent in acid resistance and can reduce contact resistance.
According to the method for producing a metal separator for a fuel cell of the present invention, a metal separator for a fuel cell having excellent acid resistance and low contact resistance can be produced.

It is sectional drawing of the metal separator for fuel cells which concerns on this invention. It is a flowchart which shows the flow of the manufacturing method of the metal separator for fuel cells which concerns on this invention. (A) is the scanning microscope image which image | photographed the mode that Ta was formed into a film on the metal base material by the sputtering method of the film-forming conditions generally performed, (b) is a default in this invention. It is the scanning microscope image which image | photographed the mode that Ta was formed into a film on the metal base material by the sputtering method of the specific film-forming conditions to do. It is explanatory drawing which shows the structure of the film-forming apparatus. It is explanatory drawing explaining the measuring method of contact resistance.

  Next, the fuel cell metal separator and the method for manufacturing the same according to the present invention will be described in detail with reference to FIG. 1 as appropriate. FIG. 1 is a cross-sectional view of a fuel cell metal separator according to the present invention.

  As shown in FIG. 1, a metal separator 1 for a fuel cell according to the present invention is a metal substrate 2 having a flat surface or a concave gas flow path (not shown) formed on at least a part of the surface. A metal separator for a fuel cell manufactured by using an acid-resistant metal film 3 and a conductive alloy film 4 on the surface of the metal substrate 2.

As the metal base 2, it is preferable to use any metal material selected from pure titanium, titanium alloy, stainless steel, pure aluminum, aluminum alloy, pure copper, and copper alloy because of excellent conductivity. Specifically, a base material of 1 to 4 types of pure titanium specified in JIS H 4600, a Ti alloy such as Ti-Al, Ti-Ta, Ti-6Al-4V, Ti-Pd, or SUS304, A stainless steel such as SUS316, or a base material of pure aluminum, aluminum alloy, pure copper, or copper alloy can be used.
From the viewpoint of cost, it is preferable to use pure aluminum, an aluminum alloy, or stainless steel, and from the viewpoint of acid resistance, it is preferable to use pure titanium or a titanium alloy. However, the metal material of the metal substrate 2 that can be used for the fuel cell metal separator of the present invention is not limited to these, and other metal materials that can be used for the fuel cell as a metal separator are also available. It goes without saying that it can be used.

The metal substrate 2 is preferably formed in advance with a concave gas flow path on at least a part of the surface thereof before the acid-resistant metal film 3 and the conductive alloy film 4 are formed. Furthermore, since the metal separator 1 for a fuel cell according to the present invention may be a so-called flat plate separator in which a gas flow path is not formed, when used as such a flat plate separator, the surface is flat. That is, you may use the flat metal base material 2 in which the above-mentioned gas flow path is not formed.
In addition, when forming this gas flow path, it can form by processing at least one part of the surface so that a concave shape (concave part) may be exhibited by a conventionally well-known press process, cutting process, an etching process, etc. If it does in this way, gas can be distribute | circulated in this recessed part when it assembles | assembles as a fuel cell. The gas channel may have any shape, and the shape is not particularly limited.

Acid-resistant metal film 3, Zr, Nb, consisting of any one non-noble metals selected from Ta.
Zr, Nb, since Ta is a metal that exhibits excellent acid resistance, is formed on the metal substrate 2, Zr, Nb, acid-resistant metal film 3 made of either one of the non-noble metals selected from Ta Thereby, the elution of the metal of the metal base material 2 can be prevented. In addition, the non-noble metal used for the acid-resistant metal film 3 is not limited to Zr, Nb, and Ta, and any non-noble metal can be used as long as the metal is excellent in acid resistance. For example, Hf, Al, P, or the like doped with Si can be used.

  The film thickness of the acid resistant metal film 3 is preferably 5 nm or more. If the acid-resistant metal film 3 has a film thickness of less than 5 nm, pinholes are likely to be formed in the acid-resistant metal film 3, and the metal of the metal substrate 2 may be eluted. The film thickness of the acid resistant metal film 3 is more preferably 7 nm or more. On the other hand, the upper limit of the film thickness of the acid-resistant metal film 3 is not particularly limited, but is preferably 500 nm or less from the viewpoint of time and cost required for the step S1 for forming the acid-resistant metal film described later, The thickness is more preferably 300 nm or less, and further preferably less than 100 nm.

The conductive alloy film 4 includes one or more kinds of noble metals selected from Au and Pt and one or more kinds of non-noble metals selected from Zr, Nb and Ta on the acid-resistant metal film 3 described above. Become.
Au and Pt are not only excellent in acid resistance but also an element that does not form an oxide film on the surface in an acidic atmosphere, among metal elements generally called noble metals. Can keep. Note that the noble metal used for the conductive alloy film 4 is a fuel cell in which a voltage (potential difference) is only about 0.7 V, such as a direct methanol fuel cell using methanol as a fuel, or operated under such operating conditions. The fuel cell is not limited to Au and Pt, and any precious metal can be used as long as it is excellent in acid resistance and does not form an oxide film on its surface in an acidic atmosphere. For example, Pd, Rh, Ru, etc. can also be used.

  The composition of the non-noble metal (one or more selected from Zr, Nb, Ta) in the conductive alloy film 4 is preferably 5 to 65 atomic%. By forming an alloy film by alloying a noble metal and a non-noble metal with the composition described above, the adhesion between the acid-resistant metal film 3 and the conductive alloy film 4 can be improved, so that the acid-resistant metal film 3 is conductive. The possibility of peeling from the conductive alloy film 4 can be reduced, and the conductivity can be maintained. Further, by using the noble metal and non-noble metal of the conductive alloy film 4 alloyed with the above-described composition, the amount of expensive noble metal used can be suppressed, and the conductive alloy film has conductivity and acid resistance. Can be manufactured at low cost.

  When the composition of the non-noble metal in the conductive alloy film 4 is less than 5 atomic%, the adhesion between the conductive alloy film 4 and the acid-resistant metal film 3 is poor. There is a possibility that the conductive alloy film 4 is peeled off. Further, if the composition of the non-noble metal in the conductive alloy film 4 exceeds 65 atomic%, a non-noble metal passive film is formed on the surface, which may lower the conductivity. The composition of the non-noble metal in the conductive alloy film 4 is more preferably 15 to 55 atomic%, and further preferably 25 to 45 atomic%.

  The thickness of the conductive alloy film 4 is preferably 2 nm or more. If the film thickness of the conductive alloy film 4 is less than 2 nm, a passive film is formed between the conductive alloy film 4 and the acid-resistant metal film 3, and the contact resistance is increased by peeling off the conductive alloy film 4. To do. The film thickness of the conductive alloy film 4 is preferably 5 nm or more, and more preferably 7 nm or more. On the other hand, the upper limit of the film thickness of the conductive alloy film 4 is not particularly limited, but is preferably 500 nm or less from the viewpoint of time and cost required for the step S2 for forming the conductive alloy film described later.

  The metal separator 1 for a fuel cell according to the present invention described above has an acid-resistant metal film 3 having excellent acid resistance on a metal substrate 2, and is excellent only in acid resistance. Furthermore, since it has further the electroconductive alloy film 4 which does not form an oxide film in an acidic atmosphere, it is excellent in acid resistance and can make contact resistance low.

Such a fuel cell metal separator 1 can be suitably manufactured by a method for manufacturing a fuel cell metal separator described later.
Hereinafter, the manufacturing method of the metal separator for fuel cells according to the present invention will be described with reference to FIG. 2 as appropriate. In addition, FIG. 2 is a flowchart which shows the flow of the manufacturing method of the metal separator for fuel cells which concerns on this invention.

As shown in FIG. 2, the method for manufacturing a fuel cell metal separator according to the present invention uses a metal substrate 2 having a flat surface or a concave gas flow path formed on at least a part of the surface. This is a method for producing a metal separator for a fuel cell, comprising: a step S1 for forming an acid-resistant metal film; and a step S2 for forming a conductive alloy film.
The step S1 for forming the acid-resistant metal film includes at least one selected from Zr, Nb, and Ta on the metal substrate 2 by a PVD (Physical Vapor Deposition) method for generating plasma during the film forming step. An acid-resistant metal film 3 containing a non-noble metal is formed. The reason why the film is formed using one or more kinds of non-noble metals selected from Zr, Nb, and Ta and the reason why it is preferable to form the acid-resistant metal film 3 until the film thickness becomes 5 nm or more have already been described. Since it is as described, the description is omitted.

Since Zr, Nb, and Ta, which are acid-resistant metals, are all high-melting-point metals, when an acid-resistant metal film is formed by a film-forming method such as a vacuum vapor deposition method that does not generate plasma, a metal substrate When particles (which refer to atoms or ions; the same shall apply hereinafter) come to the surface of the metal substrate and form crystals to form an acid-resistant metal film, the metal substrate surface is difficult to diffuse and is porous. It becomes a film and forms a pinhole. Therefore, for example, when immersed in an acidic solution, even if an acid-resistant metal film is formed on the metal substrate, the acidic solution penetrates from the pinhole portion, and the metal of the metal substrate is eluted. That is, in order to prevent the metal of the metal substrate from eluting, it is necessary to eliminate the formation of pinholes in the acid-resistant metal film.
Therefore, in order to form a dense acid-resistant metal film that does not form pinholes, it is necessary to form the film by ion plating or sputtering, which is a PVD method that generates plasma. Note that it is more preferable to use Unbalanced Magnetron Sputtering (UBMS) as the sputtering method.

  In the step S1 for forming the acid-resistant metal film, the metal substrate 2 is heated and the voltage is applied to form the acid-resistant metal film 3 on the metal substrate 2. As conditions, it is preferable that the heating condition of the metal substrate 2 is 50 ° C. or more, and the voltage application condition of the metal substrate 2 is − (minus) 50 V or less. If the PVD method satisfying such heating conditions and voltage application conditions is performed, energy can be applied to Ta, Zr, and Nb particles to activate surface diffusion and facilitate movement on the surface of the metal substrate. The film can be densified and pinholes can be eliminated. In other words, by heating the metal substrate 2 and applying thermal energy to the Ta, Zr, and Nb particles adhering to the surface of the metal substrate, the kinetic energy of the Ta, Zr, and Nb particles is increased, and surface diffusion is activated. be able to.

  When the heating condition of the metal substrate 2 in step S1 for forming the acid-resistant metal film is less than 50 ° C. or the voltage application condition to the metal substrate 2 is higher than − (minus) 50V, the metal substrate 2 is sputtered. Since the energy of the sputtered particles that diffuse on the surface 2 is low, many pinholes are formed in the acid-resistant metal film 3 (see FIG. 3A described later). The heating condition and voltage application condition of the metal substrate 2 are more preferably 100 ° C. or more and − (minus) 100V or less, and further preferably 200 ° C. or more and − (minus) 200V or less.

Sputtering (that is, generating plasma) without applying voltage to the metal substrate 2 and heating it under the film forming conditions generally used for the acid-resistant metal film 3 such as Zr, Nb, and Ta. When the film is formed under sputtering conditions that are not allowed to occur, pinholes are formed in the acid-resistant metal film on the metal substrate, as shown in FIG.
However, in the step S1 for forming an acid-resistant metal film, the metal substrate 2 is heated at 50 ° C. or more, and the surface diffusion of sputtered particles is accelerated by applying a voltage at − (minus) 50V or less. A uniform and dense acid-resistant metal film 3 as shown in FIG. 3B, in which no pinhole is formed, can be formed. FIG. 3A shows the conditions of a conventional film forming process, that is, a Ta acid-resistant metal film is formed without heating a metal substrate made of pure titanium and without applying a voltage. FIG. 5 is a TEM image (magnification: 75000 times) obtained by imaging the cross section with a transmission electron microscope (TEM), and FIG. It is the TEM image (magnification: 75000 times) which formed the acid-resistant metal film of Ta on the metal base material made from titanium, and imaged the cross section with TEM. In both (a) and (b), the scale bar in the photograph indicates 200 nm.
The acid-resistant metal film shown in FIGS. 3A and 3B is formed under the film formation conditions shown in Table 1 below.

As shown in FIG. 3 (a), the acid-resistant metal film formed under the conditions of the conventional film forming process is such that Ta crystals extend from the metal substrate in a columnar shape, and pinholes are formed in the crystal grain boundaries. It can be seen that many are formed.
On the other hand, as shown in FIG. 3B, the acid-resistant metal film formed in step S1 for forming an acid-resistant metal film that satisfies the above-described conditions is formed by densely forming Ta crystals. It can be seen that no pinholes are formed.
In addition, when these were immersed in 80 degreeC and 1M sulfuric acid aqueous solution for 100 hours, and the weight reduction | decrease amount, ie, the amount of dissolution, was measured, the metal base material which formed the acid-resistant film | membrane shown in FIG. Although dissolution of 04 mg / cm ² was observed, no decrease in weight was observed for the metal substrate on which the acid-resistant film shown in FIG. 3B was formed. From this, it can be seen that the acid-resistant metal film in step S1 for forming the acid-resistant metal film of the present invention exhibits excellent acid resistance.

Next, the step S2 for forming the conductive alloy film is selected from one or more precious metals selected from Au and Pt, and Zr, Nb, and Ta on the acid-resistant metal film 3 by the PVD method. A conductive alloy film 4 containing at least one non-noble metal is formed.
The reason why the film is formed using one or more kinds of noble metals selected from Au and Pt and one or more kinds of non-noble metals selected from Zr, Nb and Ta, and the film thickness of the conductive alloy film 4 are as follows. The reason why it is preferable to form a film up to 2 nm or more is as described above, and the description thereof is omitted.
The conductive alloy film 4 is more preferably formed by a sputtering method because an alloyed film can be formed and its composition can be freely controlled.

  According to the manufacturing method of the metal separator for a fuel cell of the present invention described above, the uniform and dense acid-resistant metal film 3 is formed on the metal substrate 2, and further on the acid resistance and contact resistance. By forming the excellent conductive alloy film 4, it is possible to manufacture the fuel cell metal separator 1 having excellent acid resistance and low contact resistance.

  Next, the fuel cell metal separator and the method for producing the same according to the present invention will be specifically described with reference to Examples that satisfy the requirements of the present invention and Comparative Examples that do not satisfy the requirements of the present invention.

[Example A]
Eighteen types of pure titanium metal substrates (2 cm × 5 cm × 1 mm) defined in JIS H 4600 were prepared and ultrasonically cleaned with acetone to obtain test plates. Film formation was performed by Unbalanced Magnetron Sputtering (UBMS) under the conditions shown in Table 2 below. A UBMS202 apparatus (manufactured by Kobe Steel) was used as the film forming apparatus.

As shown in Table 3 below, one of Zr, Nb, and Ta was used as a target for the acid-resistant metal film attached to one electrode in the chamber. Further, as a target for the conductive alloy film, a predetermined amount of Zr, Nb and Ta chips attached on Au or Pt was attached to the other electrode in the chamber. The structure of the film forming apparatus is shown in FIG. In addition, the test board revolved the fixed base, and also formed the film on both sides and side surfaces of the test board by rotating the test board.
Table 3 shows the noble and non-noble metal species used for the conductive alloy films of test plates 1 to 18, the composition (%) and film thickness (nm) of the non-noble metal in the conductive alloy film, and the acid-resistant metal film. Non-noble metal species and film thickness are shown.

In Table 3, the composition (atomic%) of the non-noble metal in the conductive alloy film was measured by ICP emission analysis. In the ICP emission analysis method, a conductive alloy film is formed on a test plate in advance, and the test plate is dissolved in an acid solution (aqua regia / hydrofluoric acid) that can dissolve both the titanium substrate and the conductive alloy film. The concentration of the noble metal element and the non-noble metal element constituting the conductive alloy film was measured, and the composition ratio (atomic%) based on the result was clearly shown. The aqua regia / hydrofluoric acid mixed solution is an acid solution having a hydrochloric acid concentration of 38%, nitric acid 70% and hydrofluoric acid 48%, respectively, and a volume ratio of hydrochloric acid 3: nitric acid 1: hydrofluoric acid 2+ distilled water 6. It was prepared as follows.
The film thicknesses of the conductive alloy film and acid-resistant metal film were calculated from the sputter rate for each target used and estimated from the values.

For test plates 1 to 18 shown in Table 3, a load resistance of 98 N (10 kgf) was applied using the contact resistance measuring device 30 shown in FIG. 5 to measure the contact resistance. That is, both surfaces of the test plates 1 to 18 are sandwiched between carbon cloths C and C, and the outside is pressurized with 98 N using copper electrodes 31 and 31 having a contact area of 1 cm ² , and a current of 1 A using a DC current power supply 32 The voltage applied between the carbon cloths C and C was measured with a voltmeter 33, and the contact resistance was calculated.

Moreover, the acid resistance test was done about the test plates 1-18. At that time, other portions of the test plates 1 to 18 were masked so that only the 1 cm × 1 cm portions of the center both surfaces of the metal substrate were exposed. This is immersed in an aqueous sulfuric acid solution (0.5 mol / l) at 80 ° C. for 100 hours, washed and dried, then the masking material is removed, and the weight loss is measured using a microbalance capable of measuring up to 1 μg. Thereafter, the contact resistance was measured using the contact resistance device 30 in the same manner as described above. In addition, the contact resistance after heat treatment and after sulfuric acid immersion was 15 mΩ · cm ² or less, and the weight loss after sulfuric acid immersion was 0.02 mg / cm ² or less.
Table 4 below shows the contact resistance (mΩ · cm ² ) of the test plates 1 to 18 after immersion in sulfuric acid and the weight loss (mg / cm ² ) after immersion in sulfuric acid.

  As shown in Table 4, the test plates 1 to 4, 9, 10, 13, 14, and 17 are composed of the noble metal species and the non-noble metal species used in the conductive alloy film, and the composition of the non-noble metal in the conductive alloy film ( Atomic%) and film thickness (nm), as well as the non-noble metal species and film thickness of the acid-resistant metal film satisfied the requirements of the present invention, so the results of contact resistance after sulfuric acid immersion and weight loss after sulfuric acid immersion passed. (Example (refer to the remarks column in Table 4)).

  On the other hand, since the test plates 6 and 11 have a low non-noble metal composition in the conductive alloy film, the adhesion between the conductive alloy film and the acid-resistant metal film is poor, and the conductive alloy film is peeled off to form the acid-resistant metal film. A passive film was formed and the contact resistance increased.

Since the test plates 5, 12, and 18 had a large composition of non-noble metals in the conductive alloy film, the acid-resistant metal film formed a passive film on the surface, so the contact resistance increased and the test plate did not pass. (Comparative example (see remarks column in Table 4)).
Since the test plates 7 and 16 have a thin acid-resistant metal film, the portion where the metal substrate is exposed increases due to the formation of pinholes in the acid-resistant metal film. A decrease was observed, and the contact resistance increased due to the oxide film formed on the surface of the metal substrate, and the test was not successful (Comparative Example (see the remarks column in Table 4)).
Since the test plates 8 and 15 are thin in the conductive alloy film, a passive film is formed between the conductive alloy film and the acid-resistant metal film. None (comparative example (see remarks column in Table 4)).

  In addition, according to JIS K 5400, when a cross-cut tape peeling test was conducted by applying a tape to the surface of the test plate 1 as an example of the present invention, peeling of the acid-resistant metal film and the conductive alloy film was recognized. I couldn't.

[Example B]
As the metal base material, six metal substrates made of pure titanium having the same standard as [Example A] were prepared, and the conductive alloy film was formed under the metal base heating conditions and metal base voltage application conditions shown in Table 5 below. Was made of Au-Ta, the composition was Ta 45 atomic%, the film thickness was 20 nm, the acid-resistant metal film was Ta, and the film thickness was fixed to 10 nm to form test plates 19-24.

The test plates 19 to 24 produced implemented under the conditions shown in Table 5 under the same conditions as Example A], the contact resistance after immersion sulfate (mΩ · cm ^2), and weight loss after sulfuric acid immersion (mg / cm ² ) was evaluated. The results are shown in Table 6 below.

  In the test plates 19 to 21, the heating condition of the metal substrate was 50 ° C. or more, and the voltage application condition of the metal substrate was less than − (minus) 50 V. The result of weight reduction passed and became an example (see the remarks column in Table 6).

  On the other hand, the test plates 22 to 24 had pinholes in the acid-resistant metal film because the heating condition of the metal substrate was less than 50 ° C. or the voltage application condition of the metal substrate was larger than − (minus) 50V. As a result, the metal substrate was exposed and exposed to an acidic atmosphere, and the metal of the metal substrate was eluted. Therefore, the weight after sulfuric acid immersion decreased, and the contact resistance after sulfuric acid immersion increased, and it did not pass (comparative example (refer remarks column of Table 6)).

  The fuel cell metal separator of the present invention and the method for producing the same have been specifically described with reference to the best mode and examples for carrying out the invention. However, the gist of the present invention is not limited to these descriptions. Rather, it should be construed broadly based on the claims. Needless to say, various changes and modifications based on these descriptions are also included in the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Metal separator for fuel cells 2 Metal base material 3 Acid-resistant metal film 4 Conductive alloy film S1 Process to form acid-resistant metal film S2 Process to form conductive alloy film

Claims (5)

A metal separator for a fuel cell manufactured using a metal substrate having a flat surface or a concave gas flow path formed on at least a part of the surface,
On the surface of the metal substrate,
Zr, Nb, consisting of any one non-noble metals selected from Ta, and the acid-resistant metal film of less than thickness of 5nm or more 100 nm,
The acid-resistant metal film includes one or more noble metals selected from Au and Pt and one or more non-noble metals selected from Zr, Nb, and Ta, and the non-noble metals are contained in 5 to 65 atoms. % Naru comprise a thickness possess a more conductive alloy film 2 nm, a,
In the PVD method, the acid-resistant metal film is formed on the metal substrate by applying a voltage of −50 V or less while heating the metal substrate to 50 ° C. or more. Metal separator for fuel cell.   2. The fuel cell according to claim 1, wherein the metal substrate is made of any metal material selected from pure titanium, titanium alloy, stainless steel, pure aluminum, aluminum alloy, pure copper, and copper alloy. Metal separator. A method for producing a fuel cell metal separator produced using a metal substrate having a flat surface or a concave gas flow path formed on at least a part of the surface,
On the surface of the metal substrate, a step of forming by PVD method, Zr, Nb, consisting of any one non-noble metals selected from Ta, the acid-resistant metal film of less than thickness of 5nm or more 100 nm,
On the acid-resistant metal film, the PVD method includes at least one noble metal selected from Au and Pt and at least one non-noble metal selected from Zr, Nb, Ta, and the non-noble metal. Forming a conductive alloy film having a film thickness of 2 nm or more,
In the PVD method, the acid-resistant metal film is formed on the metal substrate by applying a voltage of −50 V or less while heating the metal substrate to 50 ° C. or higher. A method for producing a metal separator for a fuel cell, wherein   The method for manufacturing a metal separator for a fuel cell according to claim 3, wherein the PVD method is an ion plating method or a sputtering method.   The metal substrate is any one of metal materials selected from pure titanium, titanium alloy, stainless steel, pure aluminum, aluminum alloy, pure copper, and copper alloy. Manufacturing method of metal separator for fuel cell.