JP2010180457A - Method for manufacturing corrosion-resistant electroconductive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for effectively manufacturing a corrosion-resistant electroconductive material superior in corrosion resistance and electroconductivity. <P>SOLUTION: The method for manufacturing the corrosion-resistant electroconductive material includes: a plating step of immersing at least one part of a Ti-based substrate made from pure titanium (Ti) or Ti alloy into an Ni-plating solution containing nickel (Ni) as a main component to form a plated Ni layer on a surface of the Ti-based substrate; and a nitriding step of nitriding the Ti-based substrate which has been subjected to the plating step, at 880°C or lower. Thereby obtained corrosion-resistant electroconductive material has a corrosion-resistant electroconductive film which is superior in at least one of corrosion resistance and electroconductivity formed on the surface of at least one part of the Ti-based substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a corrosion-resistant conductive material having a corrosion-resistant conductive film based on titanium (Ti) and having excellent corrosion resistance or conductivity on the surface.

  As represented by metal separators for polymer electrolyte fuel cells and the like, recently, there has been a demand for a member that can achieve high levels of both corrosion resistance and conductivity. However, it is not easy to obtain a corrosion-resistant conductive member (corrosion-resistant conductive material) that can achieve both of them at an industrial level where various things are required.

  For example, a Ti-based or stainless-based metal material forms a strong and stable passive film on the surface and exhibits excellent corrosion resistance. However, since the passive film is made of a stable insulating compound, it usually has very high resistance and poor conductivity. In order to obtain a practical corrosion-resistant conductive material, various proposals as disclosed in the following patent documents have been made.

JP 2005-336551 A JP 2004-273370 A JP 2000-353531 A JP 2000-123850 A

  Patent Document 1 proposes that a heat treatment is performed on a Ti material to form an Fe-concentrated phase, thereby improving the corrosion resistance of the Ti material. However, Patent Document 1 does not disclose the conductivity of the Ti material. In addition, complicated thermomechanical processing is required to form such an Fe-concentrated phase.

  Patent Document 2 proposes a separator in which TiB boride particles are crystallized in a Ti base material. In this separator, the corrosion resistance is secured by the passive film on the substrate, and the conductivity is expressed by the boride crystallized on the surface. However, since the boride is very hard, the separator is inferior in rollability and formability. Of course, if the amount of boride dispersed is reduced, the formability and rollability are improved, but the conductivity is lowered. Moreover, corrosion may progress from the part from which the boride is detached.

  Patent Document 3 proposes a separator in which a metal nitride layer is formed on the surface of a Ti-based substrate. When this inventor tested this separator, it turned out that although the contact resistance before an electrolytic corrosion test is certainly reduced, the contact resistance after an electrolytic corrosion test increases greatly.

  Patent Document 4 proposes a separator in which a chemically very stable noble metal plating layer is provided on a base material made of stainless steel, titanium alloy, or the like. However, the use of such precious metals is expensive. Further, when the amount of noble metal used is reduced, there is a risk of deterioration of adhesion and peeling of the plating layer. Furthermore, when the base material is Al or the like, a local battery is formed at the pinhole portion of the plating layer, and local corrosion such as pitting corrosion may occur on the base material.

  This invention is made in view of such a situation, and provides the manufacturing method which can manufacture efficiently the corrosion-resistant electrically conductive material provided with the corrosion-resistant conductive film from which at least one of corrosion resistance or electroconductivity is obtained stably. The purpose is to do.

  As a result of extensive research and trial and error, the present inventor conducted nitriding treatment on a Ni-P plated Ti-based substrate, thereby providing stable corrosion resistance and high corrosion resistance. Succeeded in forming a conductive film. Furthermore, the present inventor has succeeded in obtaining a new corrosion-resistant conductive film exhibiting the same corrosion resistance as that of the above-described film even when the substrate subjected to Ni-B plating is subjected to nitriding treatment.

  Based on such circumstances, the present inventor has developed these results to complete the method for producing a corrosion-resistant conductive material of the present invention.

<< Corrosion-resistant conductive material manufacturing method (Ni plating method) >>
(1) That is, in the method for producing a corrosion-resistant conductive material of the present invention, at least a part of a Ti-based substrate made of pure titanium (Ti) or a Ti alloy is immersed in a Ni plating solution containing nickel (Ni) as a main component. And a plating step of forming a Ni plating layer on the surface of the Ti-based substrate,
A nitriding step of nitriding the Ti-based substrate after the plating step at 880 ° C. or lower;
And a corrosion-resistant conductive material in which a corrosion-resistant conductive film excellent in at least one of corrosion resistance and conductivity is formed on at least a part of the surface of the Ti-based substrate.

  According to this Ni plating method, a corrosion-resistant conductive material or a polymer electrolyte fuel cell separator having a corrosion-resistant conductive film exhibiting excellent corrosion resistance conductivity, which will be described in detail later, can be obtained relatively easily and stably. be able to. In the present specification, the above-described method for producing a corrosion-resistant conductive material is referred to as a Ni plating method.

  (2) The reason, mechanism, and the like that an excellent corrosion-resistant conductive film is formed relatively easily by the Ni plating method are currently under investigation and the details are not necessarily clear. However, as a result of investigation and research by the inventor, Ni—P plating containing P (including Ni—P—Fe plating) and Ni—B plating containing B are the above in terms of characteristics and practicality. It is known to be effective as Ni plating.

  In addition, by forming the treatment temperature in the nitriding treatment step below the α-β solid phase transformation temperature of the Ti-based material, specifically, 880 ° C. or less, excellent characteristics and good formation on the surface of the Ti-based substrate are achieved. A corrosion-resistant conductive material having a corrosion-resistant conductive film formed can be obtained.

<Corrosion-resistant conductive material>
(1) This invention is grasped | ascertained not only as a manufacturing method of a corrosion-resistant electrically conductive material but as a corrosion-resistant electrically conductive material which provided the corrosion-resistant electrically conductive film on the surface of a base material.

  That is, the present invention may be a corrosion-resistant conductive material comprising a base material and the above-mentioned corrosion-resistant conductive film formed on at least a part of the surface of the base material.

  Here, the base material does not ask | require material, a shape, a magnitude | size, etc. For example, a member having a predetermined shape may be used, or a material, powder, or the like to be processed or molded from now on. Therefore, the corrosion-resistant conductive material referred to in the present invention can include not only a member having a corrosion-resistant conductive film but also a material itself that is a raw material or a raw material.

  (2) By the way, the corrosion-resistant conductive material obtained by the production method of the present invention can satisfy both corrosion resistance and conductivity at a high level at the same time. However, the present invention is not limited to this, and is specialized only in one of corrosion resistance or conductivity. It may be the case. For example, the above-mentioned corrosion-resistant conductive material is suitable for a member that requires only high corrosion resistance and a member that requires only high conductivity. By using the above-mentioned corrosion-resistant conductive material, it is possible to use a Ti-based material having a lower purity than that of the prior art, and to reduce the manufacturing cost. Depending on the required specifications of the member, the composition and formation method of the corrosion-resistant conductive film can be changed as appropriate, and either one of the corrosion resistance or the conductivity can be given priority over the other.

  The base material referred to in the present invention does not necessarily need to be entirely Ti-based. As long as Ti is present in the surface layer portion to be coated and the corrosion-resistant conductive film of the present invention is formed, the base (core portion) of the base material may be another metal such as Fe (including stainless steel), May be resin, ceramic or the like.

  (3) The above corrosion-resistant conductive material can be efficiently obtained by a Ni plating method described later using a Ni—P plating solution or a Ni—B plating solution. Therefore, the corrosion-resistant conductive material is grasped as follows.

  (I) That is, the present invention is a corrosion-resistant or conductive material comprising Ti-based substrate made of pure Ti or Ti alloy, and Ti, Ni, N and P formed on at least a part of the surface of the Ti-based substrate. It may be a corrosion-resistant conductive material characterized by comprising a corrosion-resistant conductive film excellent in at least one of them. However, Ni diffuses from the Ni-P plating layer to the Ti-based substrate side and may not be included in the corrosion-resistant conductive film.

  This corrosion-resistant conductive film preferably contains 3 to 20% by mass (hereinafter simply referred to as “%” as appropriate) of P when the total film is 100% by mass. Further, the corrosion-resistant conductive film may contain Fe.

  (Ii) The present invention also provides a corrosion-resistant or conductive material comprising Ti-based substrate made of pure Ti or Ti alloy, and Ti, Ni, N and B formed on at least a part of the surface of the Ti-based substrate. It may be a corrosion-resistant conductive material characterized by comprising a corrosion-resistant conductive film excellent in at least one of them. However, Ni diffuses from the Ni—B plating layer to the Ti-based substrate side and may not be included in the corrosion-resistant conductive film.

  The corrosion-resistant conductive film preferably contains 0.1 to 2% by mass of B when the entire film is 100% by mass.

<Solid polymer fuel cell and its separator>
This invention is grasped | ascertained also as a separator for polymer electrolyte fuel cells which is a typical form of said corrosion-resistant electrically-conductive material.

That is, the present invention is provided with a solid polymer electrolyte membrane provided in the center, a fuel electrode provided in contact with one side of the solid polymer electrolyte membrane, and in contact with the other side of the solid polymer electrolyte membrane. A unit cell consisting of an oxidation electrode and a fuel electrode and a separator provided outside the oxidation electrode is laminated,
In the polymer electrolyte fuel cell that supplies fuel gas between the separator and the fuel electrode and supplies oxidant gas between the separator and the oxidation electrode to generate DC power,
The separator is a separator for a polymer electrolyte fuel cell characterized by having the above-mentioned corrosion-resistant conductive film on at least a part of the surface, and at least having excellent corrosion resistance and conductivity on the corrosion-resistant conductive film. Is preferable.

  Furthermore, this invention is grasped | ascertained also as a polymer electrolyte fuel cell using the separator.

<Additional configuration>
In addition to the above-described configuration, the method for producing a corrosion-resistant conductive material of the present invention further includes one or two or more arbitrarily selected from (i) to (xi) listed below. Also good.

  It should be noted that a configuration selected from the following can be added to a plurality of inventions in a superimposed manner and arbitrarily. For convenience, the corrosion-resistant conductive material (including the corrosion-resistant conductive film) itself and its manufacturing method are described separately, but any of the configurations shown below can be appropriately combined with each other across categories. For example, as long as it is a constituent element of a corrosion-resistant conductive film, it goes without saying that it is related to the corrosion-resistant conductive material and the manufacturing method thereof. Moreover, even if it seems to be a configuration related to “method” at first glance, it can be a configuration related to “thing” if it is understood as a product-by-process.

  (I) The Ni plating solution is a Ni-P plating solution containing P, and the Ni plating layer is a Ni-P plating layer. The P concentration in the Ni-P plating solution is 0.5 to 20% by mass, and further 1 to 10% by mass. For example, P may be added to the Ni—P plating solution in the form of sodium hypophosphite at 0.01 to 0.2 mol / l.

  (Ii) The Ni-P plating layer contains 7 to 20% by mass of P when the entire plating layer is 100% by mass.

  (Iii) The Ni—P plating solution is a Ni—P—Fe plating solution further containing Fe.

  (Iv) The Ni-P plating layer is a Ni-P-Fe plating layer.

  (V) The Ni plating solution is a Ni-B plating solution further containing B, and the Ni plating layer is a Ni-B plating layer. The B concentration in the Ni-B plating solution is 0.1 to 1% by mass.

  (Vi) The Ni-B plating layer contains 0.1 to 2% by mass of B when the entire plating layer is 100% by mass.

  (Vii) The plating step is performed by electroless plating.

  (Viii) The nitriding step is a gas nitriding step for holding the Ti-based substrate in a nitriding gas containing N.

(Ix) The nitriding gas includes nitrogen (N ₂ ) gas or ammonia (NH ₃ ) gas.

(X) The nitriding gas includes N ₂ gas and hydrogen (H ₂ ) gas.

  (Xi) The nitriding step is an ion nitriding step for holding the Ti-based substrate in nitrogen plasma.

<Others>
(1) The “corrosion resistant conductive material” referred to in the present specification may be in any form as described above. Not only a product shape or a member having a shape close thereto, but may be a material such as an ingot shape, a rod shape, a tubular shape, a plate shape, or a raw material such as a powder.

  (2) It is difficult to specify exactly the composition of a very thin corrosion-resistant conductive film. If it dares to specify, it is sufficient if it is a film containing Ti, Ni and N, and at least one of corrosion resistance and conductivity is developed. However, as described above, Ni diffuses from the Ni plating layer to the Ti-based substrate side and may not be included in the corrosion-resistant conductive film.

  However, the corrosion-resistant conductive film may contain some elements other than the above-described elements such as a modified element that improves or does not deteriorate the characteristics of the corrosion-resistant conductive film. For example, such elements include Cr, Mn, Co, B, Al, rare earth elements (Sc, Y, rhetanoid, actinoid) and the like.

  Further, the corrosion-resistant conductive film can also contain “unavoidable impurities” in addition to the modifying element. Inevitable impurities are elements that are difficult to remove for cost or technical reasons. Such inevitable impurities may be inevitably mixed during the formation of the corrosion-resistant conductive film as well as when originally contained in the base material. Examples of unavoidable impurities include Li, Na, Mg, K, Ca, V, Ni, Cu, O, and Cl.

  However, in the case of the present invention, even if it is inevitable impurities when viewed from the base material on which the corrosion-resistant conductive film is formed, it is not inevitable impurities when viewed from the corrosion-resistant conductive film itself, or is effective for improving the characteristics of the corrosion-resistant conductive film In addition, there are some which are essential constituent elements of the corrosion-resistant conductive film. For example, Fe that is an impurity of a Ti-based substrate can be an essential constituent element when viewed from the corrosion-resistant conductive film of the present invention.

  When the entire corrosion-resistant conductive film is 100% by mass, the modifying element is preferably 80% or less, more preferably 70% or less. Moreover, inevitable impurities are good to be less than 15% and also less than 10%. The ratio here is the total amount of inevitable impurities.

  Usually, the proportion of inevitable impurities is often smaller than the proportion of essential constituent elements. However, the inevitable impurities are not limited to those that inhibit the corrosion resistance or conductivity of the corrosion-resistant conductive film, and the elements of the corrosion-resistant conductive film that do not deteriorate but do not improve the characteristics are also included in the inevitable impurities. It is. When such an element is an unavoidable impurity, the abundance ratio may be relatively large. Further, when there are various kinds of inevitable impurities and a small amount, the existence ratio is easily influenced by the accuracy and characteristics of the detection device. For example, when calculated from XPS data, the amount of inevitable impurities may increase.

  (3) “Corrosion resistance” as used herein may be excellent in at least one of the characteristics such as acid resistance that does not corrode even in an acid atmosphere and oxidation resistance that does not oxidize in an oxygen atmosphere. “Conductivity” only needs to be excellent in at least one of the characteristics, such as when the electrical resistance of the film itself is small, or when the contact resistance that causes a problem when contacting with another conductive material is small.

  Unless otherwise specified, “x to y” in the present specification includes the lower limit x and the upper limit y. In addition, it should be noted that the lower limit and the upper limit described in the present specification can be arbitrarily combined to constitute a range such as “ab”.

It is a schematic diagram which shows the measuring apparatus of contact resistance. It is a graph which shows the relationship between the electrolytic corrosion test regarding each test piece, and contact resistance. It is a graph which shows the relationship between the electrolytic corrosion test regarding each test piece, and contact resistance. 4 is a graph showing a relationship between an electrolytic corrosion test and a contact resistance with respect to a test piece 31. It is sectional drawing which shows 1 cell of the polymer electrolyte fuel cell which concerns on a present Example. It is a disassembled perspective view of 1 cell of the polymer electrolyte fuel cell which concerns on a present Example.

  The present invention will be described in more detail with reference to embodiments of the invention.

  In this specification, the Ni plating method will be mainly described. However, the basic examples of the corrosion-resistant conductive film, the corrosion-resistant conductive material, and the application examples of the corrosion-resistant conductive material are described in detail. Clarify the contents of the Ni plating method. Which embodiment is the best depends on the target, required performance, and the like.

<Method for producing corrosion-resistant conductive material or method for forming corrosion-resistant conductive film>
(1) Plating step In the plating step, a Ti-based substrate is immersed in a Ni plating solution containing Ni as a main component, and a Ni plating layer is formed on the surface of the substrate. The plating may be electrolytic plating or electroless plating, but it is more preferable that the surface of the substrate having a complex shape can be plated with a uniform thickness and has excellent covering ability. Although the thickness of a plating layer is suitably adjusted according to the thickness of a corrosion-resistant conductive film, 0.1-5 micrometers is preferable. As the Ni plating solution, a Ni—P plating solution, a Ni—P—Fe plating solution, or a Ni—B plating solution may be used. Electroless plating using these plating solutions can be easily performed. However, the elements constituting the Ni plating layer are not necessarily supplied from the plating solution. Elements other than Ni may be supplied from the substrate side or the like.

(2) Nitriding process N is introduced into the corrosion-resistant conductive film by the nitriding process. As a result, a chemically stable nitride is formed, and corrosion resistance conductivity is ensured. Further, O introduced into the corrosion-resistant conductive film before the nitriding step is removed by reduction or the like.

  This nitriding method includes gas nitriding (including gas soft nitriding), ion nitriding (plasma nitriding), salt bath nitriding (including salt bath soft nitriding (tuftride)), and the like. In particular, in the present invention, gas nitriding or ion nitriding capable of nitriding at a relatively low processing temperature is preferable. In gas nitriding, N can be introduced into the corrosion-resistant conductive film with a relatively easy apparatus or process. In ion nitriding, N is introduced into the corrosion-resistant conductive film in a short time.

Gas nitriding is performed by holding the substrate after the above-described pretreatment in a high-temperature atmosphere filled with N ₂ gas, NH ₃ gas, or a mixed gas containing one or more of them. These nitriding gases themselves may flow. In particular, gas nitridation using NH ₃ gas has a higher nitriding power than gas nitridation using pure N ₂ gas, and thus is sufficiently nitrided even at a processing temperature of 880 ° C. or lower. In addition, when NH ₃ gas is used, a nitriding atmosphere can be formed by simply flowing NH ₃ gas into a furnace in which the substrate is accommodated and replacing it with gas (air) that was previously in the furnace. Therefore, it is an inexpensive process because it is not necessary to evacuate the furnace. Examples of the mixed gas include a mixed gas of N ₂ gas and H ₂ gas. Even if the processing temperature is 880 ° C. or less, the mixed gas is sufficiently nitrided.

  The nitriding step is performed at a processing temperature not higher than the α-β solid phase transformation temperature of the Ti-based substrate. Specifically, it is preferably 880 ° C. or lower, more preferably 650 to 850 ° C. The processing temperature is the temperature of the Ti base material during nitriding. If the treatment temperature is 880 ° C. or lower, the internal α-β solid phase transformation temperature of Ti is not exceeded, so that the internal residual stress of the corrosion-resistant conductive film is small, and deformation and peeling are small. Further, even when the treatment temperature is low, N is sufficiently introduced into the corrosion-resistant conductive film, and excellent corrosion resistance or conductivity is imparted. Furthermore, since the processing temperature is low, oxidation of the corrosion-resistant conductive film is suppressed. In the case of gas nitriding, the treatment time is preferably 0.05 to 3 hours, more preferably 0.5 to 2 hours. The treatment time is appropriately adjusted in the above range depending on the gas composition and the amount of N introduced.

  Needless to say, it is desirable to prevent the Ti-based substrate from being exposed to an environment exceeding 880 ° C. not only in the nitriding step but in all steps. Even if there is a heat treatment step or the like, it is preferably performed at 880 ° C. or lower.

<Application>
The method for producing a corrosion-resistant conductive material of the present invention can be used for a separator for a polymer electrolyte fuel cell, a current-carrying member, etc. in addition to a Ti corrosion-resistant film.

  Further, according to the research of the present inventor, it is known that the above-described corrosion-resistant conductive film obtained through the nitriding process is not oxidized under a corrosive environment of about pH 4 (oxygen does not combine with the film). Therefore, the corrosion-resistant conductive film subjected to nitriding can exhibit not only excellent oxidation resistance but also stable conductivity even in an oxidizing atmosphere. Furthermore, since the corrosion-resistant conductive film has a tendency to release oxygen in a high-temperature nitrogen atmosphere, the corrosion-resistant conductive material of the present invention can also be used as a high-temperature oxidation-resistant material.

  The present invention will be described more specifically with reference to examples.

<Manufacture of test pieces>
Various Ni plating processes shown below were applied to a Ti substrate (Ti base material) made of pure titanium (JIS type 1).

[Example 1]
(1) Ni-P plating treatment The aforementioned Ti substrate was immersed in a Ni-P plating solution, and a Ni-13% P plating layer of about 2.5 μm was formed on the surface by an electroless plating method. Top Nicolon P-13 (Okuno Pharmaceutical Co., Ltd.) was used as the Ni-P plating solution.

To this Ni-P plated Ti substrate, subjected to gas nitriding by _{N 2} gas atmosphere (gas nitriding process), to obtain a test piece 11. In gas nitriding, a Ti substrate on which a Ni—P plating layer is formed is placed in a mixed gas stream of N ₂ : 98% by volume and H ₂ : 2% by volume, processing temperature: 850 ° C., processing time: Performed in 2 hours.

(2) Ni-B plating treatment The above-mentioned Ti substrate was immersed in a Ni-B plating solution, and a Ni-B plating layer of about 2.5 μm was formed on the surface by an electroless plating method. As the Ni-B plating solution, Top Chemialoy (Okuno Pharmaceutical Co., Ltd.) was used.

The Ni—B plated Ti substrate was subjected to gas nitriding in an N ₂ gas atmosphere (gas nitriding step) to obtain a test piece 12. Gas nitriding is carried in a heat treatment furnace in which a Ti substrate on which a Ni—B plating layer is formed is evacuated, and in a mixed gas atmosphere of N ₂ : 98% by volume and H ₂ : 2% by volume, a processing temperature: 850 ° C., Treatment time: 2 hours.

[Example 2]
(3) Ni-P-Fe plating treatment A Ni-P-Fe plating solution was prepared using nickel nitrate, iron sulfate, and sodium hypophosphite. The Ti substrate described above was immersed in this plating solution, and a Ni—P—Fe plating layer of about 2.5 μm was formed on the surface by an electroless plating method. The composition of the formed plating layer was Fe / (Ni + Fe) 0.2.

This Ni—P—Fe plated Ti substrate was housed in a heat treatment furnace, and a mixed gas of argon (Ar) and ammonia (NH ₃ ) was passed through the heat treatment furnace to perform gas nitriding (gas nitriding step). The gas composition at this time was Ar: 98% by volume, NH ₃ : 2% by volume, and processing temperature: 850 ° C. Three types of test pieces were obtained with a treatment time of 30 minutes (test piece 21), 1 hour (test piece 22), and 2 hours (test piece 23).

[Example 3]
(3 ′) Ni—P—Fe plating treatment A Ni—P—Fe plating solution was prepared using nickel nitrate, iron sulfate, and sodium hypophosphite. The Ti substrate described above was immersed in this plating solution, and a Ni—P—Fe plating layer of about 1 μm was formed on the surface by electroless plating. The composition of the formed plating layer was Fe / (Ni + Fe) 0.2.

The Ni—P—Fe plated Ti substrate was subjected to gas nitriding in an NH ₃ gas atmosphere (gas nitriding step), and a test piece 31 was obtained. The gas nitriding was performed by placing a Ni—P—Fe plated Ti substrate in a heat treatment furnace and flowing a mixed gas of argon (Ar) and ammonia (NH ₃ ) through the heat treatment furnace. The gas flow rates at this time were Ar: 200 mL / min, NH ₃ : 100 mL / min, processing temperature: 750 ° C., processing time: 1 hour.

<Evaluation of specimen>
The contact resistance of each of the above test pieces and the contact resistance after these test pieces were immersed in a corrosive solution were measured. The corrosive solution used was prepared by adding 5 ppm F ⁻ and 10 ppm Cl ⁻ to dilute sulfuric acid (pH 4) and maintaining at 80 ° C. The applied corrosion voltage was 0.26 V (vs. Pt), and the corrosion test time was 100 hours.

  The contact resistance was measured as shown in FIG. That is, each test piece S and carbon paper 105 were sandwiched between two gold-plated copper plates 161 and 162, and a constant current of 1 A was passed from the constant-current DC power source 107 between the gold-plated copper plates 161 and 162. At this time, a load F having an air pressure of 1.47 MPa was applied between the gold-plated copper plates 61 and 62. After holding in this state for 60 seconds, the potential difference V between the gold-plated copper plates 161 and 162 was measured. Based on this, the contact resistance R (= V / A) was calculated. The results are shown in FIGS.

  As a comparative example, the Ti substrate was similarly nitrided at 1000 ° C. for 2 hours, and the contact resistance before and after the electrolytic corrosion test was measured for the test piece C1 coated with TiN. The results are also shown in FIG.

As is apparent from each graph, the test pieces 11, 12, 21 to 23 and 31 produced by the Ni plating method show a contact resistance of only about 10 mΩ · cm ² even when the electrolytic corrosion test is performed for about 100 hours. There was almost no increase in contact resistance. That is, even when the nitriding temperature was 850 ° C. or less, a corrosion-resistant conductive film excellent in corrosion resistance and conductivity could be formed. On the other hand, in the test piece C1 coated with TiN, the contact resistance after 90 hours increased to about ²⁰ mΩ · cm ² .

  The test pieces 21 to 23 are samples having different processing times in the gas nitriding step. Even with the test piece 21 having a treatment time of 30 minutes, the contact resistance hardly increased. Further, the test piece 31 had a Ni—P—Fe plating layer thickness of 1 μm and was thinner than the plating layers of other test pieces, but the increase in contact resistance due to corrosion was suppressed.

《Polymer fuel cell》
As one embodiment of the corrosion-resistant conductive material according to the present invention, FIGS. 5A and 5B show a solid polymer fuel cell comprising a solid polymer fuel cell separator having a corrosion-resistant conductive film formed on the surface of a Ti substrate.

  The solid polymer fuel cell utilizes the fact that a solid polymer electrolyte membrane having a proton exchange group in the molecule functions as a proton conductive electrolyte. Specifically, as shown in FIGS. 5A and 5B, in the polymer electrolyte fuel cell F, the oxidation electrode 2 and the fuel electrode 3 are joined to both sides of the polymer electrolyte membrane 1, respectively. Further, a separator 5 is disposed outside the electrodes via a gasket 4. The separator 5 on the oxidation electrode 2 side is provided with an air supply port 6 and an air discharge port 7, and the separator 5 on the fuel electrode 3 side is provided with a hydrogen supply port 8 and a hydrogen discharge port 9.

  In the separator 5, a plurality of grooves 10 extending in the flow direction of the hydrogen g and the air o are formed for conduction and uniform distribution of the hydrogen g and the air o. Further, the cooling water w fed from the water supply port 11 circulates inside the separator 5 and is then discharged from the drain port 12. The water cooling mechanism built in the separator 5 suppresses overheating of the solid polymer electrolyte membrane and the like due to heat generated during power generation.

  Hydrogen g sent from the hydrogen supply port 8 into the gap between the fuel electrode 3 and the separator 5 becomes protons that have released electrons, passes through the solid polymer electrolyte membrane 1, and passes through the gap between the oxidation electrode 2 and the separator 5. It reacts with oxygen in the passing air o and burns. Then, electric power can be supplied to the load between the oxidation electrode 2 and the fuel electrode 3.

  In general, a fuel cell has a very small amount of power generation per cell. For this reason, by stacking a plurality of cells with one unit between the pair of separators 5 and 5, a desired output (power is ensured. However, when a large number of cells are stacked, the separator 5 and each electrode 2, 3 is increased, the power loss is also increased, and the power generation efficiency of the polymer electrolyte fuel cell F is likely to be lowered.

  Here, since the separator 5 of the present example has a corrosion-resistant conductive film having excellent conductivity on the surface layer, the contact resistance between the oxidation electrode 2 and the fuel electrode 3 is reduced while ensuring the corrosion resistance. The Therefore, by using the corrosion-resistant conductive material according to the present embodiment, it is possible to easily obtain a separator for a polymer electrolyte fuel cell that is excellent in workability, impact resistance, and the like and that achieves both corrosion resistance and conductivity.

S: Test piece F: Solid polymer fuel cell 1: Solid polymer electrolyte membrane 2: Fuel electrode 3: Oxidation electrode 5: Separator

Claims (9)

At least a part of a Ti base material made of pure titanium (Ti) or a Ti alloy is immersed in a Ni plating solution containing nickel (Ni) as a main component to form a Ni plating layer on the surface of the Ti base material. A plating process,
A nitriding step of nitriding the Ti-based substrate after the plating step at 880 ° C. or lower;
And a corrosion-resistant conductive material having a corrosion-resistant conductive film excellent in at least one of corrosion resistance and conductivity on the surface of at least a part of the Ti-based substrate is obtained. Method. The Ni plating solution is a Ni-P plating solution further containing phosphorus (P),
The method for producing a corrosion-resistant conductive material according to claim 1, wherein the Ni plating layer is a Ni—P plating layer. The Ni-P plating solution is a Ni-P-Fe plating solution further containing iron (Fe),
The method for producing a corrosion-resistant conductive material according to claim 2, wherein the Ni—P plating layer is a Ni—P—Fe plating layer. The Ni plating solution is a Ni-B plating solution further containing boron (B),
The method for producing a corrosion-resistant conductive material according to claim 1, wherein the Ni plating layer is a Ni—B plating layer.   The said plating process is a manufacturing method of the corrosion-resistant electrically-conductive material in any one of Claims 1-4 performed by electroless plating.   The method for producing a corrosion-resistant conductive material according to claim 1, wherein the nitriding step is a gas nitriding step for holding the Ti-based substrate in a nitriding gas containing nitrogen (N). The nitriding gas is nitrogen (N ₂₎ gas or ammonia (NH ₃₎ manufacturing method of the corrosion-resistant conductive material of claim 6, further comprising a gas. The method of manufacturing a corrosion-resistant conductive material according to claim 7, wherein the nitriding gas includes N ₂ gas and hydrogen (H ₂ ) gas.   The method for producing a corrosion-resistant conductive material according to claim 1, wherein the nitriding step is an ion nitriding step of holding the Ti-based substrate in nitrogen plasma containing N.

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