Titanium material or titanium alloy material having surface electrical conductivity, and fuel cell separator and fuel cell using the same

Abstract

The composition ratio of a titanium hydride [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 found from the maximum intensity of metal titanium (I.sub.Ti) and the maximum intensity of the titanium hydride (I.sub.TiH) of the X-ray diffraction peaks measured at a surface of a titanium or a titanium alloy at an incident angle to the surface of 0.3 is 55% or more, a titanium oxide film is formed on an outermost surface of the titanium or the titanium alloy, and C is at 10 atomic % or less, N is at 1 atomic % or less, and B is at 1 atomic % or less in a position where the surface has been subjected to sputtering of 5 nm with argon. The titanium oxide film is formed by performing stabilization treatment after performing passivation treatment in prescribed aqueous solutions, and has a thickness of 3 to 10 nm.

Claims

1. A titanium material or a titanium alloy material, wherein the composition ratio of a titanium hydride [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 found from the maximum intensity of metal titanium (I.sub.Ti) and the maximum intensity of the titanium hydride (I.sub.TiH) of the X-ray diffraction peaks measured at a surface of a titanium or a titanium alloy at an incident angle to the surface of 0.3 is 55% or more, a titanium oxide film is formed on an outermost surface of the titanium or the titanium alloy, C is at 10 atomic % or less, N is at 1 atomic % or less, and B is at 1 atomic % or less in a position where the surface has been subjected to sputtering of 5 nm with argon, and each of the amounts of increase in contact resistance from before to after deterioration test 1 and deterioration test 2 below is 10 mcm.sup.2 or less, deterioration test 1: immersion for 4 days in a sulfuric acid solution at 80 C. and pH 3 containing 2 ppm F ions, deterioration test 2: application of an electric potential of 1.0 V (vs. SHE) for 24 hours in a sulfuric acid solution at 80 C. and pH 3.

2. A fuel cell separator comprising the titanium material or the titanium alloy material according to claim 1.

3. A polymer electrolyte fuel cell comprising the fuel cell separator according to claim 2.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagram showing X-ray diffraction profiles (XRDs) of the surface of a titanium material or a titanium alloy material. (a) shows an XRD of the surface of a conventional material serving as a comparison (a surface after common pickling with nitrohydrofluoric acid), and (b) and (c) show XRDs of the surface of a titanium material or a titanium alloy material of the present invention (the present invention materials 1 and 2).

(2) FIG. 2 is a diagram showing the results of X-ray photoelectron spectroscopy (XPS) of the surfaces of two titanium materials or titanium alloy materials of the present invention. (a) shows the result of X-ray photoelectron spectroscopy (XPS) of the surface of one titanium material or titanium alloy material, and (b) shows the result of X-ray photoelectron spectroscopy (XPS) of the surface of the other titanium material or titanium alloy material.

(3) FIG. 3 is a diagram showing a transmission electron microscope image of a cross section immediately below the surface of a titanium material or a titanium alloy material of the present invention.

(4) FIG. 4 is a diagram showing the relationships between the value of [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 (Formula (1)) found from the result of X-ray diffraction measured at the surface of a titanium material or a titanium alloy material, the contact resistance with carbon paper after a deterioration test of the material, and the amount of increase in the contact resistance from before to after the deterioration test. Both deterioration tests 1 and 2 mentioned above are shown.

DESCRIPTION OF EMBODIMENTS

(5) In The titanium material or a titanium alloy material of the present invention (hereinafter occasionally referred to as the present invention material), which can be suitable for a fuel cell separator having good contact-to-carbon electrical conductivity and good durability, the intensities of the X-ray diffraction peaks of the surface satisfy Formula (1) below, and a titanium oxide film is formed on the outermost surface. The composition ratio of a hydride [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 is preferably 60% or more. When the composition ratio of the hydride [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 is 60% or more, each of the amounts of increase in the contact resistance from before to after deterioration test 1 and deterioration test 2 described later is 4 mcm.sup.2 or less.
[I.sub.TiH/(I.sub.Ti+I.sub.TiH)]10055%(1)

(6) I.sub.TiH: the maximum intensity of the X-ray diffraction peaks of the titanium hydride (TiH, TiH.sub.1.5, TiH.sub.2, or the like)

(7) I.sub.Ti: the maximum intensity of the X-ray diffraction peaks of metal Ti

(8) I.sub.TiH/(I.sub.Ti+IT.sub.i-H) is an index that indicates the composition ratio between metal titanium and the titanium hydride at the surface of the titanium material or the titanium alloy material, and a larger value of the index means a phase configuration containing a larger amount of the titanium hydride.

(9) The X-ray diffraction is performed by oblique incidence in which the incident angle of X-ray is fixed to a low angle, for example to 0.3, with respect to the surface of the titanium material or the titanium alloy material. By the X-ray diffraction, the structure immediately below the surface can be identified.

(10) In the present invention material, a titanium oxide film is formed on the outermost surface. By performing X-ray photoelectron spectroscopy on the surface of the titanium material or the titanium alloy material, a peak is detected in a Ti 2p spectrum at the position of the binding energy of TiO.sub.2, which is a titanium oxide, i.e. approximately 459.2 eV. By the detection, the formation of the titanium oxide film can be confirmed.

(11) The thickness of the titanium oxide is preferably 3 to 10 nm. The thickness of the titanium oxide film can be measured by, for example, observing a cross section immediately below the surface with a transmission electron microscope.

(12) A method for producing the present invention material (hereinafter occasionally referred to as the present invention material production method) is performed by performing the following on a titanium material or a titanium alloy material:

(13) (i) forming a titanium hydride on the outer layer of the titanium material or the titanium alloy material, and then

(14) (ii) performing passivation treatment and stabilization treatment in prescribed aqueous solutions.

(15) The treatment that forms a titanium hydride on the outer layer of the titanium material or the titanium alloy material (hereinafter occasionally referred to as hydride formation treatment) is not particularly limited to a specific method. For example, (x) a method in which the titanium material or the titanium alloy material is immersed in hydrochloric acid or sulfuric acid, which is a non-oxidizing acid, (y) a method in which the titanium material or the titanium alloy material is cathodically electrolyzed, and (z) a method in which the titanium material or the titanium alloy material is subjected to heat treatment in a hydrogen-containing atmosphere are given. A titanium hydride can be formed on the outer layer of the titanium material or the titanium alloy material by any of these methods.

(16) The aqueous solution used for the passivation treatment is an aqueous solution in which an oxidizing agent such as nitric acid or chromic acid is added. The prescribed aqueous solution used for the stabilization treatment is an aqueous solution containing rice flour, wheat flour, potato starch, corn flour, soybean flour, a pickling corrosion inhibitor, or the like, which is a naturally derived substance or an artificially synthesized substance containing one or more of an amine-based compound, an aminocarboxylic acid-based compound, a phospholipid, a starch, calcium ions, and polyethylene glycol, and also the aqueous solution used for the passivation treatment is an ordinary aqueous solution.

(17) The present invention material is produced such that, in the titanium oxide film of the outermost surface and immediately below it, the amount of carbides, nitrides, carbonitrides, and/or borides of titanium is reduced within the extent of practical usability as a separator, in view of costs as well.

(18) When at least one of C, N, and B is present as an unavoidably mixed-in element in the titanium base material, a carbide, a nitride, a carbonitride, and/or a boride of titanium may be formed during the heat treatment process. To suppress the formation of carbides, nitrides, carbonitrides, and/or borides of titanium to the extent possible, the total amount of C, N, and B contained in the titanium base material is preferably set to 0.1 mass % or less. It is more preferably 0.05 mass % or less.

(19) In the present invention material, it is preferable that a titanium compound containing at least one of C, N, and B not be present in the titanium oxide film, and it is preferable that the amount of titanium compounds containing at least one of C, N, and B be reduced within the extent of practical usability as a separator since this causes a large cost increase. The effect of the present invention is exhibited when C is at 10 atomic % or less, N at 1 atomic % or less, and B at 1 atomic % or less as a result of an analysis of the surface using X-ray photoelectron spectroscopy (XPS) after the surface is subjected to sputtering of 5 nm with argon.

(20) Here, the depth of argon sputtering is the value converted from the sputtering rate when the sputtering is performed on SiO.sub.2. Since a peak is detected in a Ti 2p spectrum also from the surface after sputtering of 5 nm at the position of the binding energy of TiO.sub.2, which is a titanium oxide, i.e. approximately 459.2 eV, the result is an analysis result of the interior of the titanium oxide film.

(21) For the data analysis, MutiPak V. 8.0, an analysis software application produced by Ulvac-phi, Incorporated, was used.

(22) It has been known that the contact resistance of the surface is a relatively small value in a state where oil components of cold rolling remain or in a state where a carbide, a nitride, and/or a carbonitride of titanium, which is an electrically conductive substance, is dispersed on the surface due to heating in a nitrogen gas atmosphere. However, in the state as it is, during the exposure to an acidic corrosion environment of the actual use, these titanium compounds are dissolved and re-precipitated as an oxide that inhibits the contact electrical conductivity, and reduce the contact electrical conductivity.

(23) The present invention will now be described in more detail with reference to the drawings.

(24) The present invention material can be obtained by, for example, forming a titanium hydride near the surface of a titanium base material by hydride formation treatment, then performing passivation treatment in an aqueous solution in which an oxidizing agent such as nitric acid or chromic acid is added, and performing stabilization treatment with a prescribed aqueous solution.

(25) FIG. 1 shows X-ray diffraction profiles (XRDs) of the surface of a titanium material or a titanium alloy material for a fuel cell separator. In FIG. 1(a) shows an XRD of the surface of a conventional material serving as a comparison (a surface after common pickling with nitrohydrofluoric acid), and FIGS. 1(b) and 1(c) show XRDs of the surface of a titanium material or a titanium alloy material for a fuel cell separator of the present invention (the present invention material). In the present invention example 1 shown in (b), the composition ratio of the titanium hydride [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 is 63%, and in the present invention example 2 shown in (c), the composition ratio of the titanium hydride [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 is 55%.

(26) For the X-ray diffraction peaks, in the conventional material of (a), only diffraction peaks of metal titanium (the circle marks in the drawing) are detected; on the other hand, in the present invention materials of (b) and (c), very strong peaks of a titanium hydride (the inverted triangle marks in the drawing) are detected. The titanium hydride is found to be TiH.sub.1.5 from the positions of the diffraction peaks. Here, the element concentration distribution in the depth direction from the surface was measured by glow discharge optical emission spectrometry, and it has been found that hydrogen is concentrated in an outer layer portion.

(27) Here, the method of the X-ray diffraction measurement and the method for identifying the diffraction peaks are described. The X-ray diffraction profile was measured by oblique incidence in which the incident angle of X-ray was fixed to 0.3 with respect to the surface of the titanium material or the titanium alloy material, and the diffraction peaks thereof were identified.

(28) Using SmartLab, an X-ray diffraction apparatus manufactured by Rigaku Corporation, Co-K (wavelength: =1.7902 ) was used for the target at an incident angle of 0.3, and a W/Si multiple-layer film mirror (on the incident side) was used for the K removal method. The X-ray source load power (tube voltage/tube current) is 9.0 kW (45 kV/200 mA). The analysis software application used is X'pert HighScore Plus produced by Spectris Co., Ltd.

(29) The measured X-ray diffraction profile can be compared to a database in which a titanium hydride such as ICDD Card No. 01-078-2216, 98-002-1097, 01-072-6452, or 98-006-9970 is used as the reference material; thereby, the diffraction peaks can be identified.

(30) The depth of X-ray entry in the measurement conditions mentioned above is approximately 0.18 m for metal titanium and approximately 0.28 m for the titanium hydride, and therefore the X-ray diffraction peaks are X-ray diffraction peaks that reflect the structure extending approximately 0.2 to 0.3 m in depth from the surface.

(31) In FIG. 2, photoelectron spectra of Ti 2p measured by XPS of the outermost surface of the present invention material are shown. In FIG. 3, a transmission electron microscope image of a cross section immediately below the surface of the present invention material is shown. As shown in FIG. 2, a very strong peak is detected from the outermost surface at the position of the binding energy of TiO.sub.2, which is a titanium oxide, i.e. approximately 459.2 eV.

(32) In FIG. 3, a portion 2 in a bright (whitish) film form which covers Ti 1 is a titanium oxide film. Ti and O are detected from this portion by energy dispersive spectrometry (EDS), and it is found that a titanium oxide film is formed in this portion.

(33) Also in the conventional material, when the titanium oxide film is subjected to a prescribed passivation treatment and stabilization treatment, the durability to a simple acidic environment is enhanced, but in a corrosion environment in which fluorine is contained or in a usage environment in which an electric potential is applied, there is a case where the durability cannot be maintained. This applies also to a titanium alloy in which a platinum group element, Au, or Ag is added. The impurity level of platinum group elements is less than 0.005 mass % and when the total amount of platinum group elements, Au, and Ag contained is less than 0.005 mass %, this case is regarded as a titanium alloy (titanium) in which a platinum group element, Au, or Ag is added.

(34) In the conventional material, when the concentration of fluoride ions is 2 ppm or more, the contact resistance with carbon paper is increased to approximately 100 m.Math.cm.sup.2 or more, and the amount of increase in the contact resistance is approximately 90 m.Math.cm.sup.2 or more, but in the present invention material, the contact resistance with carbon paper is as low as 10 to 20 m.Math.cm.sup.2 or less even when the concentration of fluoride ions is 2 to 5 ppm, and the amount of increase in the contact resistance can be suppressed to 10 mcm.sup.2 or less at most, in a preferred case to 4 mcm.sup.2 or less, and high tolerance is exhibited to fluorine.

(35) Thus, in the present invention material, in deterioration test 1 in which immersion is performed at 80 C. for 4 days in a sulfuric acid aqueous solution adjusted to pH 3 and containing 2 ppm F ions, the amount of increase in the contact resistance with carbon paper after the deterioration test is 10 mcm.sup.2 or less at a surface pressure of 10 kgf/cm.sup.2. It is preferably 4 mcm.sup.2 or less. For reference, the value of the contact resistance after deterioration test 1 is 20 m.Math.cm.sup.2 or less, preferably 10 m.Math.cm.sup.2 or less.

(36) In deterioration test 2 in which an electric potential of 1.0 V (vs. SHE) is applied for 24 hours in a sulfuric acid aqueous solution at 80 C. and pH 3, the amount of increase in the contact resistance with carbon paper after the deterioration test is 10 mcm.sup.2 or less at a surface pressure of 10 kgf/cm.sup.2. It is preferably 4 mcm.sup.2 or less. For reference, in the present invention material, the value of the contact resistance after deterioration test 2 is as low as 20 m.Math.cm.sup.2 or less, preferably as low as 10 m.Math.cm.sup.2 or less, and high tolerance can be maintained even when an electric potential is applied. On the other hand, in the conventional material, the value of the contact resistance is as high as approximately 30 m.Math.cm.sup.2, and the amount of increase in the contact resistance is as high as approximately 20 m.Math.cm.sup.2.

(37) Each of deterioration tests 1 and 2 can measure the tolerance (the degree of stability) to fluorine and the applied voltage by means of the amount of increase in the contact resistance. As the test time whereby a significant difference can be identified sufficiently, 4 days and 24 hours are selected, respectively. In general, there is seen a tendency for the contact resistance to increase almost linearly with the test time, and when the value has become approximately 30 m.Math.cm.sup.2 or more, increase rapidly thereafter.

(38) In view of the fact that the contact resistance varies depending on the carbon paper used, the contact resistance measured using TGP-H-120 produced by Toray Industries, Inc. was taken as the standard in the deterioration test.

(39) The present inventors have thought up the idea that the contact resistance of the present invention material being stable at a lower level than existing contact resistances is caused by the titanium hydride formed on the outer layer. With focus on the X-ray diffraction peaks from the titanium hydride shown in FIG. 1, the present inventors made extensive studies on the correlation between the X-ray diffraction intensity of metal titanium (Ti) and the X-ray diffraction intensity from the titanium hydride (TiH).

(40) The results are shown in FIG. 4. The [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 on the horizontal axis was found from the result of identification of the diffraction peaks in the X-ray diffraction profile measured by oblique incidence in which the incident angle of X-ray was fixed to 0.3 with respect to the surface of the titanium or the titanium alloy material.

(41) [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 is an index of the composition ratio between metal titanium and the titanium hydride at the surface of the titanium or the titanium alloy material, and quantitatively indicates that a larger value of the index corresponds to a phase configuration containing a larger amount of the titanium hydride. The vertical axis represents the contact resistance measured by performing deterioration tests 1 and 2 and the amount of increase in the contact resistance. In each case, stabilization treatment was performed after passivation treatment was performed, in prescribed aqueous solutions. After that, deterioration test 1 described above (immersion at 80 C. for 4 days in a sulfuric acid aqueous solution at pH 3 with a fluoride ion concentration of 2 ppm) and deterioration test 2 described above (application of an electric potential of 1.0 V (vs. SHE) for 24 hours in a sulfuric acid aqueous solution at pH 3) were performed. The (vs. SHE) represents the value with respect to the standard hydrogen electrode (SHE).

(42) As shown in FIG. 4, the contact resistance after deterioration tests 1 and 2 is very low when [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 is 55% or more. The present inventors have found that, in the present invention material, the correlation of Formula (1) mentioned above exists between the X-ray diffraction intensity of metal titanium (Ti) and the X-ray diffraction intensity from the titanium hydride (TiH).

(43) Thus, in the present invention material, [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 is set to 55% or more. It is preferably set to 60% or more, where the contact resistance after the accelerated deterioration test (after deterioration tests 1 and 2) is stable at a low level as shown in FIG. 4. The upper limit thereof is 100% or less as a matter of course. The contact resistance of the objective of the present invention material has been obtained also when, in view of the fact that embrittlement due to the titanium hydride is a concern, bending-back processing was performed on a material with an [I.sub.TiH/(I.sub.Ti+I.sub.TiH)]100 of 85% which had been subjected to hydride formation treatment with hydrochloric acid.

(44) As the action of the titanium hydride, an action in which, when the titanium oxide film of the outermost surface is attacked by fluoride ions in the pickling environment, the hydrogen in the titanium promotes the repair of the damaged oxide film by virtue of the easy diffusibility of the hydrogen, an action in which the titanium oxide film of the outermost surface is ennobled by contacting the titanium hydride, an action in which, although dissolved-out titanium ions precipitate as a titanium oxide on the surface and usually increase the contact resistance, the working of the hydrogen of the titanium hydride prevents the progress of oxidation and forms a precipitate having electrical conductivity, etc. are presumed. From such actions, it is presumed that, when a film structure provided by the present application is included, the effect is sufficiently obtained regardless of whether a platinum group element, Au, or Ag is contained or not.

(45) In any of the actions, to exhibit the effect thereof, it is necessary that a prescribed amount or more of the titanium hydride be present as shown FIG. 4.

(46) After the hydride formation treatment, the present invention material is subjected to passivation treatment and stabilization treatment in prescribed aqueous solutions. By the treatments, a titanium oxide film is formed on the outermost surface as shown in FIG. 2 and FIG. 3. The thickness of the titanium oxide film is preferably 3 to 10 nm from the viewpoints of suppressing the initial contact resistance to a low level and ensuring durability to fluorine and voltage application in the environment to which the present invention material is exposed.

(47) If the thickness of the titanium oxide film is less than 3 nm, the contact resistance after the deterioration test in which fluorine is added or a voltage is applied will be more than 20 m.Math.cm.sup.2 and also the amount of increase in the contact resistance will be more than 10 m.Math.cm.sup.2, and the durability will be insufficient. On the other hand, if the thickness of the titanium oxide film is more than 10 nm, the initial contact resistance may be more than 10 m.Math.cm.sup.2.

(48) The thickness of the titanium oxide film of the outermost surface can be measured by observing a cross section immediately below the surface with a transmission electron microscope. In FIG. 3, the portion 2 in a bright (whitish) film form is the titanium oxide film.

(49) The conditions of the passivation treatment performed in a prescribed aqueous solution and the conditions of the subsequent stabilization treatment are as follows.

(50) The aqueous solution used for the passivation treatment is an aqueous solution containing an oxidizing agent such as nitric acid or chromic acid. It is presumed that the titanium oxide film is densified by the oxidizing power of them.

(51) The aqueous solution used for the stabilization treatment is an aqueous solution containing rice flour, wheat flour, potato starch, corn flour, soybean flour, a pickling corrosion inhibitor, or the like, which is a naturally derived substance or an artificially synthesized substance containing one or more of an amine-based compound, an aminocarboxylic acid-based compound, a phospholipid, a starch, calcium ions, and polyethylene glycol, and exhibits the effect of suppressing the attack from acid components, halide ions (chloride, fluoride, and the like), etc. present in the exposure environment.

(52) In the conventional material, even in a titanium oxide film formed by performing passivation treatment and stabilization treatment in aqueous solutions, a carbide, a nitride, and/or a carbonitride of titanium present in a large amount in or immediately below the titanium oxide film is dissolved out in a corrosion environment in which fluorine is contained or in a usage environment in which an electric potential is applied, and is re-precipitated as an oxide that inhibits the contact electrical conductivity.

(53) On the other hand, in the present invention material, a carbide, a nitride, and/or a carbonitride of titanium produced on the surface by bright annealing can be almost removed by removing oil components containing C etc., which cause carbide formation, with pickling cold rolling as pre-treatment after the cold rolling or by performing pickling with nitrohydrofluoric acid or hydride formation treatment after the bright annealing.

(54) As described above, the effect of the present invention has been exhibited when C is at 10 atomic % or less, N at 1 atomic % or less, and B at 1 atomic % or less as a result of an analysis of the surface using X-ray photoelectron spectroscopy (XPS) after the surface is subjected to sputtering of 5 nm with argon.

(55) After that, passivation treatment and stabilization treatment are performed in prescribed aqueous solutions; thus, a surface structure, in which the amount of carbides, nitrides, and/or carbonitrides of titanium that are likely to dissolve out is reduced within the extent of practical usability as a separator, in view of costs as well, is formed. By the surface structure, the durability in a corrosion environment in which fluorine is contained or in a usage environment in which an electric potential is applied is significantly improved.

(56) In the case where neither passivation treatment nor stabilization treatment in a prescribed aqueous solution is performed, although the initial contact resistance is low, the contact resistance is increased to approximately 30 m.Math.cm.sup.2 or more after the accelerated deterioration test.

(57) Thus, in the present invention material, the contact resistance after the accelerated deterioration test is 20 m.Math.cm.sup.2 or less. It is preferably 10 m.Math.cm.sup.2 or less. It is more preferably 8 m.Math.cm.sup.2 or less.

(58) Next, an example of the method for producing the present invention material is described.

(59) In producing a piece of foil serving as a titanium base material, in order to make it less likely for a carbide, a nitride, and/or a carbonitride of titanium to be produced on the surface, the component design described above is implemented, and the conditions of cold rolling, cleaning (including pickling), and annealing (atmosphere, temperature, time, etc.) are selected and these processes are performed. As necessary, subsequently to annealing, pickling cleaning is performed with a nitrohydrofluoric acid aqueous solution (e.g. 3.5 mass % hydrogen fluoride+4.5 mass % nitric acid).

(60) After that, the titanium base material is subjected to any one of the treatments of (x) immersion in hydrochloric acid or sulfuric acid, which is a non-oxidizing acid, (y) cathodic electrolysis, and (z) heat treatment in a hydrogen-containing atmosphere; thus, a titanium hydride (TiH, TiH.sub.1.5, or TiH.sub.2) is formed on the outer layer of the titanium or the titanium alloy material.

(61) If a large amount of the hydride is formed up to the interior of the titanium base material, the entire base material may be embrittled; thus, the method of (x) immersion in hydrochloric acid or sulfuric acid, which is a non-oxidizing acid, in which method hydrogen can be concentrated only relatively near the surface, is preferable.

(62) Subsequently, passivation treatment is performed on the outer layer on which the titanium hydride is formed. The passivation treatment is performed by, for example, immersing the titanium base material for a prescribed time in a mixed aqueous solution that is at a prescribed temperature and contains nitric acid or chromic anhydride, such as an aqueous solution containing 30 mass % nitric acid or a mixed aqueous solution containing 25 mass % chromic anhydride and 50 mass % sulfuric acid. By the passivation treatment, a stable passivated titanium oxide film is formed on the outermost surface of the titanium base material; thus, corrosion is suppressed.

(63) The temperature of the aqueous solution mentioned above is preferably 50 C. or more in order to improve the productivity. It is more preferably 60 C. or more, still more preferably 85 C. or more. The upper limit of the temperature is preferably 120 C. The immersion time is, depending on the temperature of the aqueous solution, generally 0.5 to 1 minute or more. It is preferably 1 minute or more. The upper limit of the immersion time is preferably 45 minutes, more preferably approximately 30 minutes.

(64) After the passivation treatment is performed, in order to stabilize the titanium oxide film, stabilization treatment is performed for a prescribed time using a stabilization treatment liquid at a prescribed temperature.

(65) The stabilization treatment liquid is an aqueous solution containing rice flour, wheat flour, potato starch, corn flour, soybean flour, a pickling corrosion inhibitor, or the like, which is a naturally derived substance or an artificially synthesized substance containing one or more of an amine-based compound, an aminocarboxylic acid-based compound, a phospholipid, a starch, calcium ions, and polyethylene glycol.

(66) For example, an aqueous solution containing a pickling corrosion inhibitor [HIBIRON (Registered Trademark No. 4787376) AS-25C, produced by Sugimura Chemical Industrial Co., Ltd.] may be used. The stabilization treatment is preferably performed for 1 to 10 minutes using a stabilization treatment liquid at 45 to 100 C.

(67) The present invention material has excellent electrical conductivity and excellent durability as described above, and is very useful as a base material for a separator for a fuel cell.

(68) The fuel cell separator using the present invention material as the base material effectively uses the surface of the present invention material as it is, as a matter of course.

(69) Also a case where a noble metal-based metal such as gold, carbon, or a carbon-containing electrically conductive film is further formed on the surface of the present invention material may be possible. In this case, in a fuel cell separator using the present invention material as the base material, even when there is a defect in the noble metal-based metal such as gold, the carbon film, or the carbon-containing film, the corrosion of the titanium base material is more suppressed than in conventional ones because the surface having excellent contact electrical conductivity and excellent corrosion resistance of the present invention material is present immediately below the film.

(70) In the fuel cell separator using the present invention material as the base material, the surface has contact electrical conductivity and durability at the same level as those of the conventional carbon separator, and furthermore is less likely to crack; thus, the quality and lifetime of the fuel cell can be ensured over a long period of time.

EXAMPLES

(71) Next, Examples of the present invention are described, but the conditions in Examples are only condition examples employed to assess the feasibility and effect of the present invention, and the present invention is not limited to these condition examples. The present invention may employ various conditions to the extent that they do not depart from the spirit of the present invention and they achieve the object of the present invention.

Example 1

(72) To assess the surface conditions and contact characteristics of the present invention intermediate material and the present invention alloy material, test materials were prepared while various conditions of the titanium or the titanium alloy material (hereinafter referred to as a titanium base material), the pre-treatment, the hydrogen treatment (the hydride formation treatment), the passivation treatment, and the stabilization treatment were changed, and the surface conditions of the titanium base material were investigated by X-ray diffraction and the contact electrical conductivity was measured by accelerated deterioration tests. The transmission electron microscope investigation image is as shown in FIG. 3. The measurement results are shown in Tables 1 to 7 together with the various conditions.

(73) [Titanium Base Material]

(74) The titanium base material (material) is as follows.

(75) M01: a titanium (JIS H 4600 type 1 TP270C); an industrial pure titanium, type 1

(76) M02: a titanium (JIS H 4600 type 3 TP480C); an industrial pure titanium, type 2

(77) M03: a titanium alloy (JIS H 4600 type 61); Al (2.5 to 3.5 mass %)-V (2 to 3 mass %)-Ti

(78) M04: a titanium alloy (JIS H 4600 type 16); Ta (4 to 6 mass %)-Ti

(79) M05: a titanium alloy (JIS H 4600 type 17); Pd (0.04 to 0.08 mass %)-Ti

(80) M06: a titanium alloy (JIS H 4600 type 19); Pd (0.04 to 0.08 mass %)-Co (0.2 to 0.8 mass %)-Ti

(81) M07: a titanium alloy (JIS H 4600 type 21); Ru (0.04 to 0.06 mass %)-Ni (0.4 to 0.6 mass %)-Ti

(82) M08: a titanium alloy; Pd (0.02 mass %)-Mm (0.002 mass %)-Ti

(83) Here, Mm is mixed rare-earth elements before isolation and purification (misch metal), and the composition of the Mm used is 55 mass % Ce, 31 mass % La, 10 mass % Nd, and 4 mass % Pr.

(84) M09: a titanium alloy; Pd (0.03 mass %)-Y (0.002 mass %)-Ti

(85) M10: a titanium alloy (JIS H 4600 type 11); Pd (0.12 to 0.25 mass %)-Ti

(86) Note: M08 and M09, which are a titanium alloy other than those in JIS standards, refer to a base material obtained by performing smelting on a laboratory scale and performing hot rolling and cold rolling.

(87) [Pre-Treatment]

(88) The pre-treatment of the titanium base material is as follows.

(89) P01: perform cold rolling up to a thickness of 0.1 mm, perform alkaline cleaning, then perform bright annealing at 800 C. for 20 seconds in an Ar atmosphere, and then clean the surface by pickling with nitrohydrofluoric acid

(90) P02: perform cold rolling up to a thickness of 0.1 mm, perform cleaning by pickling with nitrohydrofluoric acid to remove the rolling oil, and then perform bright annealing at 800 C. for 20 seconds in an Ar atmosphere

(91) P03: perform cold rolling up to a thickness of 0.1 mm, perform alkaline cleaning, and then perform bright annealing at 800 C. for 20 seconds in an Ar atmosphere

(92) In the surface cleaning with nitrohydrofluoric acid of P01 and P02, immersion was performed at 45 C. for 1 minute in an aqueous solution containing 3.5 mass % hydrogen fluoride (HF) and 4.5 mass % nitric acid (HNO.sub.3). The portion extending approximately 5 m in depth from the surface was dissolved.

(93) [Hydride Formation Treatment]

(94) (x) Pickling

(95) H01: a 30 mass % hydrochloric acid aqueous solution

(96) H02: a 30 mass % sulfuric acid aqueous solution

(97) (y) Cathodic Electrolysis Treatment

(98) H03: a pH 1 sulfuric acid aqueous solution; current density: 1 mA/cm.sup.2

(99) (z) Heat Treatment in a Hydrogen-Containing Atmosphere

(100) H04: an atmosphere (450 C.) of 20% hydrogen+80% Ar gas

(101) [Passivation Treatment]

(102) The aqueous solution used for the passivation treatment is as follows.

(103) A01: an aqueous solution containing 30 mass % nitric acid

(104) A02: an aqueous solution containing 20 mass % nitric acid

(105) A03: an aqueous solution containing 10 mass % nitric acid

(106) A04: an aqueous solution containing 5 mass % nitric acid

(107) A05: a mixed aqueous solution containing 25 mass % chromic anhydride and 50 mass % sulfuric acid

(108) A06: a mixed aqueous solution containing 15 mass % chromic anhydride and 50 mass % sulfuric acid

(109) A07: a mixed aqueous solution containing 15 mass % chromic anhydride and 70 mass % sulfuric acid

(110) A08: a mixed aqueous solution containing 5 mass % chromic anhydride and 50 mass % sulfuric acid

(111) A09: a mixed aqueous solution containing 5 mass % chromic anhydride and 70 mass % sulfuric acid

(112) Note: In each case, when a solid content occurred, the state of being dispersed in the liquid was used as it was.

(113) Note: The temperature of the aqueous solution was changed in the range of 40 to 120 C., and the immersion treatment time was changed in the range of 0.5 to 25 minutes.

(114) [Stabilization Treatment]

(115) The aqueous solution used for the stabilization treatment is as follows.

(116) B01: 0.25 mass % rice flour, the rest being ion-exchanged water

(117) B02: 0.25 mass % wheat flour, the rest being ion-exchanged water

(118) B03: 0.25 mass % potato starch, the rest being ion-exchanged water

(119) B04: 0.25 mass % corn flour, the rest being ion-exchanged water

(120) B05: 0.25 mass % soybean flour, the rest being ion-exchanged water

(121) B06: 0.02 mass % polyethylene glycol, 0.05 mass % rice flour, 0.0001 mass % calcium carbonate, 0.0001 mass % calcium hydroxide, and 0.0001 mass % calcium oxide, the rest being distilled water

(122) B07: 0.10 mass % of a pickling corrosion inhibitor [HIBIRON (Registered Trademark No. 4787376) AS-20K, produced by Sugimura Chemical Industrial Co., Ltd.], the rest being ion-exchanged water

(123) B08: 0.05 mass % of a pickling corrosion inhibitor [HIBIRON (Registered Trademark No. 4787376) AS-35N, produced by Sugimura Chemical Industrial Co., Ltd.], the rest being ion-exchanged water

(124) B09: 0.08 mass % of a pickling corrosion inhibitor [HIBIRON (Registered Trademark No. 4787376) AS-25C, produced by Sugimura Chemical Industrial Co., Ltd.], the rest being tap water

(125) B10: 0.10 mass % of a pickling corrosion inhibitor [HIBIRON (Registered Trademark No. 4787376) AS-561, produced by Sugimura Chemical Industrial Co., Ltd.], the rest being tap water

(126) B11: 0.30 mass % of a pickling corrosion inhibitor [HIBIRON (Registered Trademark No. 4787376) AS-561, produced by Sugimura Chemical Industrial Co., Ltd.], the rest being tap water

(127) B12: 0.01 mass % of a pickling corrosion inhibitor [KILESBIT (Registered Trademark No. 4305166) 17C-2, produced by Chelest Corporation], the rest being well water

(128) B13: 0.04 mass % of a pickling corrosion inhibitor (IBIT (Registered Trademark No. 2686586) New Hyper DS-1, produced by Asahi Chemical Co., Ltd.), the rest being industrial water

(129) Note: In each case, when a solid content occurred, the state of being dispersed in the liquid was used as it was.

(130) Note: The temperature of the aqueous solution was changed in the range of 45 to 100 C., and the immersion treatment time was changed in the range of 1 to 10 minutes.

(131) [Deterioration Test]

(132) Deterioration test 1 is performed by immersion for 4 days in a sulfuric acid solution at 80 C. and pH 3 containing 2 ppm F ions.

(133) Deterioration test 2 is performed by application of an electric potential of 1.0 V (vs. SHE) for 24 hours in a sulfuric acid solution at 80 C. and pH 3.

(134) [Evaluative Determination]

(135) In the amount of increase in the contact resistance, A refers to 4 mcm.sup.2 or less, B to more than 4 mcm.sup.2 and not more than 10 mcm.sup.2, and C to more than 10 mcm.sup.2. The value of the contact resistance measured using the conditions described above was 10 mcm.sup.2 or less in the case of A more than 10 and not more than 20 mcm.sup.2 in the case of B and more than 20 mcm.sup.2 in the case of C.

(136) A test piece of a prescribed size was taken from the test material that was prepared while the conditions mentioned above were changed, and the features of the surface were measured and Deterioration tests 1 and 2 were performed to measure the contact electrical conductivity. The measurement results are shown in Tables 1 to 7 together with the various conditions. For the concentrations of C, N, and B (results of XPS) out of the features of the surface in Tables, A is the case where, through an analysis of the surface using X-ray photoelectron spectroscopy (XPS) after the surface is subjected to sputtering of 5 nm with argon, it is found that C is at 10 atomic % or less, N at 1 atomic % or less, and B at 1 atomic % or less, and B is the case where, through the analysis mentioned above, it is found that any one of these elements is more than the corresponding concentration mentioned above.

(137) The results when the conditions of the titanium base material and the pre-treatment were changed are shown in Table 1.

(138) TABLE-US-00001 TABLE 1 Implementation No. 1-4 1-5 1-6 1-1 1-2 1-3 Present Present Present Comparative Comparative Comparative Invention Invention Invention Summary Example Example Example Example Example Example Material Base material M01 M01 M01 M01 M01 M02 Treatment method Pre-treatment P01 P02 P03 P02 P02 P01 Hydride formation treatment H01 H01 H01 Treatment temperature ( C.) 70 70 70 Treatment time (min) 15 25 15 Passivation treatment A01 A01 A01 Treatment temperature ( C.) 90 90 90 Treatment time (min) 10 10 10 Stabilization treatment B09 B09 B09 Treatment temperature ( C.) 100 100 100 Treatment time (min) 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 0 0 0 64 76 62 () () () Thickness of titanium oxide coating film (nm) 5 6 5 6 7 7 Concentration of C, N, and B (result of XPS) A A B A A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 40 53 15 6 6 6 conductivity After deterioration test (m .Math. cm.sup.2) 1000 1000 1000 8 7 7 Deterioration test 1 Evaluative determination C C C A A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 40 53 15 6 6 6 conductivity After deterioration test (m .Math. cm.sup.2) 1000 1000 1000 7 7 7 Deterioration test 2 Evaluative determination C C C A A A Implementation No. 1-7 1-8 1-9 1-10 1-11 1-12 Present Present Present Present Present Present Invention Invention Invention Invention Invention Invention Summary Example Example Example Example Example Example Material Base material M02 M02 M03 M04 M05 M06 Treatment method Pre-treatment P01 P02 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 70 Treatment time (min) 25 25 25 25 25 25 Passivation treatment A01 A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 90 90 Treatment time (min) 10 10 10 10 10 10 Stabilization treatment B09 B09 B09 B09 B09 B09 Treatment temperature ( C.) 100 100 100 100 100 100 Treatment time (min) 5 5 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 80 72 71 71 74 73 Thickness of titanium oxide coating film (nm) 7 5 6 6 7 6 Concentration of C, N, and B (result of XPS) A A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 6 7 7 5 6 6 Deterioration test 1 After deterioration test (m .Math. cm.sup.2) 7 8 8 8 8 8 Evaluative determination A A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 6 7 7 5 6 6 Deterioration test 2 After deterioration test (m .Math. cm.sup.2) 7 8 8 7 8 7 Evaluative determination A A A A A A Implementation No. 1-13 1-14 1-15 1-16 Present Present Present Present 1-17 1-18 Invention Invention Invention Invention Comparative Comparative Summary Example Example Example Example Example Example Material Base material M07 M08 M09 M10 M04 M05 Treatment method Pre-treatment P01 P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 70 Treatment time (min) 25 25 25 25 25 25 Passivation treatment A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 Treatment time (min) 10 10 10 10 Stabilization treatment B09 B09 B09 B09 Treatment temperature ( C.) 100 100 100 100 Treatment time (min) 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 77 78 73 74 75 74 Thickness of titanium oxide coating film (nm) 6 5 5 8 6 6 Concentration of C, N, and B (result of XPS) A A A A A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 6 5 6 6 7 7 conductivity After deterioration test (m .Math. cm.sup.2) 8 8 8 7 23 24 Deterioration test 1 Evaluative determination A A A A C C Contact electrical Before deterioration test (m .Math. cm.sup.2) 6 5 6 6 7 7 conductivity After deterioration test (m .Math. cm.sup.2) 8 7 8 7 31 30 Deterioration test 2 Evaluative determination A A A A C C Implementation No. 1-19 1-20 1-21 1-22 1-23 Comparative Comparative Comparative Comparative Comparative Summary Example Example Example Example Example Material Base material M06 M07 M08 M09 M10 Treatment method Pre-treatment P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 Treatment time (min) 25 25 25 25 25 Passivation treatment Treatment temperature ( C.) Treatment time (min) Stabilization treatment Treatment temperature ( C.) Treatment time (min) Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 73 75 73 74 74 Thickness of titanium oxide coating film (nm) 6 7 7 6 7 Concentration of C, N, and B (result of XPS) A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 6 7 6 7 6 Deterioration test 1 After deterioration test (m .Math. cm.sup.2) 24 25 23 23 22 Evaluative determination C C C C C Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 6 7 6 7 6 Deterioration test 2 After deterioration test (m .Math. cm.sup.2) 31 33 31 30 27 Evaluative determination C C C C C

(139) The results when the treatment method, the treatment time, and the treatment temperature were varied in the hydride formation treatment are shown in Table 2.

(140) TABLE-US-00002 TABLE 2 Implementation No. 2-5 2-6 2-7 2-1 2-2 2-3 2-4 Present Present Present Comparative Comparative Comparative Comparative Invention Invention Invention Summary Example Example Example Example Example Example Example Material Base material M01 M01 M01 M01 M01 M01 M01 Treatment Pre-treatment P03 P01 P01 P01 P01 P01 P01 method Hydride formation treatment H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 Treatment time (min) 5 10 15 20 25 Passivation treatment A01 A01 A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 90 90 90 Treatment time (min) 10 10 10 10 10 10 10 Stabilization treatment B09 B09 B09 B09 B09 B09 B09 Treatment temperature ( C.) 100 100 100 100 100 100 100 Treatment time (min) 5 5 5 5 5 5 5 Properties of [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 0 0 25 51 55 63 79 surface () () () () Thickness of titanium oxide coating film 6 6 7 6 6 7 7 (nm) Concentration of C, N, and B (result of B A A A A A A XPS) Contact Before deterioration test (m .Math. cm.sup.2) 5 45 6 7 6 7 7 electrical After deterioration test (m .Math. cm.sup.2) 113 192 115 72 9 8 8 conductivity Evaluative determination C C C C A A A Deterioration test 1 Contact Before deterioration test (m .Math. cm.sup.2) 5 45 16 7 6 7 7 electrical After deterioration test (m .Math. cm.sup.2) 31 67 46 26 9 8 8 conductivity Evaluative determination C C C C A A A Deterioration test 2 Implementation No. 2-8 2-9 2-10 2-11 2-12 2-13 Present Present Present Present Present Present Invention Invention Invention Invention Invention Invention Summary Example Example Example Example Example Example Material Base material M01 M01 M01 M01 M01 M01 Treatment method Pre-treatment P01 P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H02 H02 H03 H04 Treatment temperature ( C.) 70 50 50 70 50 400 Treatment time (min) 30 30 30 15 360 60 Passivation treatment A01 A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 90 90 Treatment time (min) 10 10 10 10 10 10 Stabilization treatment B09 B09 B09 B09 B09 B09 Treatment temperature ( C.) 100 100 100 100 100 100 Treatment time (min) 5 5 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 85 56 65 61 75 62 Thickness of titanium oxide coating film (nm) 7 6 7 7 6 7 Concentration of C, N, and B (result of XPS) A A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 7 7 7 7 6 6 Deterioration test 1 After deterioration test (m .Math. cm.sup.2) 8 9 8 8 8 8 Evaluative determination A A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 7 7 7 7 6 6 Deterioration test 2 After deterioration test (m .Math. cm.sup.2) 8 9 7 7 8 8 Evaluative determination A A A A A A

(141) The results when the treatment time and the treatment temperature were varied in the passivation treatment are shown in Table 3.

(142) TABLE-US-00003 TABLE 3 Implementation No. 3-1 3-2 3-3 3-4 3-5 Present Present Present Present Present Invention Invention Invention Invention Invention Summary Example Example Example Example Example Material Base material M01 M01 M01 M01 M01 Treatment method Pre-treatment P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 Treatment time (min) 25 25 25 25 25 Passivation treatment A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 90 Treatment time (min) 1 5 10 20 30 Stabilization treatment B09 B09 B09 B09 B09 Treatment temperature ( C.) 100 100 100 100 100 Treatment time (min) 5 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 77 79 79 76 78 Thickness of titanium oxide coating film (nm) 3 5 7 7 8 Concentration of C, N, and B (result of XPS) A A A A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 6 7 7 7 8 conductivity After deterioration test (m .Math. cm.sup.2) 10 8 8 8 8 Deterioration test 1 Evaluative determination A A A A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 6 7 7 7 8 conductivity After deterioration test (m .Math. cm.sup.2) 9 8 8 8 8 Deterioration test 2 Evaluative determination A A A A A Implementation No. 3-6 3-9 3-10 Present 3-7 3-8 Present Present Invention Comparative Comparative Invention Invention Summary Example Example Example Example Example Material Base material M01 M01 M01 M01 M01 Treatment method Pre-treatment P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 Treatment time (min) 25 25 25 25 25 Passivation treatment A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 25 50 100 Treatment time (min) 40 50 10 10 10 Stabilization treatment B09 B09 B09 B09 B09 Treatment temperature ( C.) 100 100 100 100 100 Treatment time (min) 5 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 80 79 77 77 78 Thickness of titanium oxide coating film (nm) 10 12 2 5 9 () () Concentration of C, N, and B (result of XPS) A A A A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 9 12 6 7 7 conductivity After deterioration test (m .Math. cm.sup.2) 14 32 76 8 8 Deterioration test 1 Evaluative determination B C C A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 9 12 6 7 7 conductivity After deterioration test (m .Math. cm.sup.2) 13 24 26 8 8 Deterioration test 2 Evaluative determination A C C A A

(143) The results when the treatment liquid was changed in the passivation treatment are shown in Table 4.

(144) TABLE-US-00004 TABLE 4 Implementation No. 4-1 4-2 4-3 4-4 4-5 Present Present Present Present Present Invention Invention Invention Invention Invention Summary Example Example Example Example Example Material Base material M02 M01 M01 M01 M01 Treatment method Pre-treatment P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 Treatment time (min) 25 25 25 25 25 Passivation treatment A01 A02 A03 A04 A05 Treatment temperature ( C.) 90 90 90 90 90 Treatment time (min) 5 5 5 5 5 Stabilization treatment B09 B09 B09 B09 B09 Treatment temperature ( C.) 100 100 100 100 100 Treatment time (min) 5 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 78 77 78 77 76 Thickness of titanium oxide coating film (nm) 7 6 6 4 8 Concentration of C, N, and B (result of XPS) A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 7 6 6 6 6 Deterioration test 1 After deterioration test (m .Math. cm.sup.2) 8 7 7 8 8 Evaluative determination A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 7 6 6 6 6 Deterioration test 2 After deterioration test (m .Math. cm.sup.2) 8 8 8 8 7 Evaluative determination A A A A A Implementation No. 4-6 4-7 4-8 4-9 Present Present Present Present Invention Invention Invention Invention Summary Example Example Example Example Material Base material M01 M01 M01 M01 Treatment method Pre-treatment P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 Treatment time (min) 25 25 25 25 Passivation treatment A06 A07 A08 A09 Treatment temperature ( C.) 90 90 90 90 Treatment time (min) 5 5 5 5 Stabilization treatment B09 B09 B09 B09 Treatment temperature ( C.) 100 100 100 100 Treatment time (min) 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 76 79 78 79 Thickness of titanium oxide coating film (nm) 6 7 4 5 Concentration of C, N, and B (result of XPS) A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 5 7 7 7 Deterioration test 1 After deterioration test (m .Math. cm.sup.2) 7 8 8 8 Evaluative determination A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 5 7 7 7 Deterioration test 2 After deterioration test (m .Math. cm.sup.2) 7 8 8 8 Evaluative determination A A A A

(145) The results when the treatment liquid was changed in the stabilization treatment are shown in Table 5.

(146) TABLE-US-00005 TABLE 5 Implementation No. 5-1 5-2 5-3 5-4 5-5 5-6 Present Present Present Present Present Present Invention Invention Invention Invention Invention Invention Summary Example Example Example Example Example Example Material Base material M01 M01 M01 M01 M01 M01 Treatment method Pre-treatment P01 P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 70 Treatment time (min) 25 25 25 25 25 25 Passivation treatment A01 A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 90 90 Treatment time (min) 10 10 10 10 10 10 Stabilization treatment B01 B02 B03 B04 B05 B06 Treatment temperature ( C.) 100 100 100 100 100 100 Treatment time (min) 5 5 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 77 78 77 76 76 79 Thickness of titanium oxide coating film (nm) 7 7 7 8 6 7 Concentration of C, N, and B (result of XPS) A A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 7 7 6 6 6 6 Deterioration test 1 After deterioration test (m .Math. cm.sup.2) 8 8 7 8 8 7 Evaluative determination A A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 7 7 6 6 6 6 Deterioration test 2 After deterioration test (m .Math. cm.sup.2) 8 8 7 7 7 7 Evaluative determination A A A A A A Implementation No. 5-7 5-8 5-9 5-10 5-11 5-12 Present Present Present Present Present Present Invention Invention Invention Invention Invention Invention Summary Example Example Example Example Example Example Material Base material M01 M01 M01 M01 M01 M01 Treatment method Pre-treatment P01 P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 70 Treatment time (min) 25 25 25 25 25 25 Passivation treatment A01 A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 90 90 Treatment time (min) 10 10 10 10 10 10 Stabilization treatment B07 B08 B10 B11 B12 B13 Treatment temperature ( C.) 100 100 100 100 100 100 Treatment time (min) 5 5 5 5 5 5 Properties of surface [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 78 79 78 78 78 78 Thickness of titanium oxide coating film (nm) 5 6 7 8 7 7 Concentration of C, N, and B (result of XPS) A A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 7 7 7 7 6 7 Deterioration test 1 After deterioration test (m .Math. cm.sup.2) 8 8 8 8 8 8 Evaluative determination A A A A A A Contact electrical conductivity Before deterioration test (m .Math. cm.sup.2) 7 7 7 7 6 7 Deterioration test 2 After deterioration test (m .Math. cm.sup.2) 8 8 8 8 7 8 Evaluative determination A A A A A A

(147) The results when the treatment temperature was varied in the stabilization treatment are shown in Table 6.

(148) TABLE-US-00006 TABLE 6 Implementation No. 6-1 6-2 6-3 6-4 6-5 6-6 6-7 Present Present Present Present Present Present Present Invention Invention Invention Invention Invention Invention Invention Summary Example Example Example Example Example Example Example Material Base material M01 M01 M01 M01 M01 M01 M01 Treatment method Pre-treatment P01 P01 P01 P01 P01 P01 P01 Hydride formation treatment H01 H01 H01 H01 H01 H01 H01 Treatment temperature ( C.) 70 70 70 70 70 70 70 Treatment time (min) 25 25 25 15 15 15 15 Passivation treatment A01 A01 A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 90 90 90 Treatment time (min) 10 10 10 10 10 10 10 Stabilization treatment B09 B09 B09 B09 B09 B09 B09 Treatment temperature ( C.) 40 60 80 40 60 80 100 Treatment time (min) 5 5 5 5 5 5 5 Properties of [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 79 78 78 56 55 55 56 surface Thickness of titanium oxide coating film (nm) 5 6 6 5 5 6 7 Concentration of C, N, and B (result of XPS) A A A A A A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 6 7 7 6 6 7 7 conductivity After deterioration test (m .Math. cm.sup.2) 15 9 8 17 10 8 8 Deterioration Evaluative determination B A A B A A A test 1 Contact electrical Before deterioration test (m .Math. cm.sup.2) 6 7 7 6 6 7 7 conductivity After deterioration test (m .Math. cm.sup.2) 14 9 8 16 9 9 8 Deterioration Evaluative determination B A A B A A A test 2

(149) The results when various conditions were changed are shown in Table 7.

(150) TABLE-US-00007 TABLE 7 Implementation No. 7-1 7-2 7-3 7-4 7-5 7-6 7-7 Present Present Present Present Present Present Present Invention Invention Invention Invention Invention Invention Invention Summary Example Example Example Example Example Example Example Material Base material M02 M02 M02 M02 M02 M03 M04 Treatment method Pre-treatment P02 P01 P01 P01 P01 P01 P01 Hydride formation treatment H01 H02 H02 H03 H04 H01 H01 Treatment temperature ( C.) 50 50 70 50 400 70 70 Treatment time (min) 30 30 15 360 60 15 15 Passivation treatment A01 A01 A01 A01 A01 A01 A01 Treatment temperature ( C.) 90 90 90 90 90 90 90 Treatment time (min) 10 10 10 10 5 5 5 Stabilization treatment B09 B09 B09 B09 B09 B09 B09 Treatment temperature ( C.) 80 80 100 100 80 80 80 Treatment time (min) 5 5 5 5 5 5 5 Properties of [I.sub.TiH/(I.sub.Ti + I.sub.TH)] 100 (%) 56 64 62 77 61 56 56 surface Thickness of titanium oxide coating film (nm) 6 6 6 5 5 6 7 Concentration of C, N, and B (result of XPS) A A A A A A A Contact electrical Before deterioration test (m .Math. cm.sup.2) 7 7 7 6 6 7 7 conductivity After deterioration test (m .Math. cm.sup.2) 9 8 8 8 8 9 9 Deterioration Evaluative determination A A A A A A A test 1 Contact electrical Before deterioration test (m .Math. cm.sup.2) 7 7 7 6 6 7 7 conductivity After deterioration test (m .Math. cm.sup.2) 9 8 8 7 8 9 8 Deterioration Evaluative determination A A A A A A A test 2

(151) From Tables 1 to 7, it is found that the contact electrical conductivity of the present invention examples is much better than the contact electrical conductivity of the comparative examples (conventional materials).

INDUSTRIAL APPLICABILITY

(152) As described above, according to the present invention, it becomes possible to provide a titanium or a titanium alloy material for a fuel cell separator having good contact-to-carbon electrical conductivity and good durability and a fuel cell separator having good contact-to-carbon electrical conductivity and good durability. When the fuel cell separator is used, the lifetime of the fuel cell can be greatly prolonged. Thus, the present invention has high applicability in battery manufacturing industries.

REFERENCE SIGNS LIST

(153) 1 Ti (titanium or titanium alloy material) 2 titanium oxide film