WO2003079476A1 - Metal member having corrosion-resistant conductive coating and process for producing the same - Google Patents

Abstract

A metal member comprising a metal base and, superimposed on its surface, a corrosion-resistant conductive coating wherein the maximum (L) of major diameters of second-phase compounds observed at the surface of metal base is 5/6-fold or less of the thickness of corrosion-resistant conductive coating (T) (L ≤ 5/6 T); and a process for producing a metal member which comprises subjecting a metal base to a zinc immersion treatment wherein zinc immersion is carried out after acid cleaning four times or more and thereafter forming a corrosion-resistant conductive coating on a surface of the metal base. In particular, a metal member having a corrosion-resistant conductive coating that can be used in a metal separator for fuel cell or an electrode of fuel cell, these being useful for fuel cell production; and a process for producing the same.

Description

 Description Metallic material with corrosion-resistant conductive film and its manufacturing method

 According to the present invention, the base material is formed of a metal material such as an aluminum material made of aluminum or an aluminum alloy, a titanium material made of titanium or a titanium alloy, a stainless steel material, and a Ni—Fe alloy material. A fuel cell separator having a conductive film, for example, a fuel cell separator interposed between the unit cells when forming a fuel cell by stacking a plurality of unit cells; an electrode of the unit cell forming the fuel cell; The present invention relates to a metal material having a corrosion-resistant conductive film useful for many uses such as an electrode material for a primary battery of a portable device, an electrode material used for electrolytic extraction of metal, and an electroplating method, and a method for producing the same. Technology background

For example, a fuel cell is composed of a plurality of unit cells composed of a pair of electrodes consisting of an anode and a force source and an electrolyte membrane of a proton conductor interposed between the electrodes, and is made of an acid-resistant, conductive material. The separator is made of a graphite material, etc., which has excellent gas permeability, and reacts with one of the electrodes between each unit cell electrode and the electrode contact surface of each separator in contact with this electrode. A gas flow path is formed, and a fuel gas such as hydrogen is supplied to the anode side of each of the unit cells, and an oxidizing gas such as oxygen and air is supplied to the cathode side, respectively. The anode gas causes an oxidation reaction of the fuel gas to generate protons and electrons.The protons move through the electrolyte membrane and are supplied to the cathode, while the electrons are extracted to an external circuit. , , In the power source de side Is a reaction between the protons that have moved through the electrolyte membrane, the electrons supplied from the external circuit, and the oxidizing gas, so that the electrons taken out to the external circuit on the anode side work as current. I'm sorry

 Such a fuel cell is capable of converting reaction energy into electric energy with extremely high efficiency, and furthermore, the reaction product is basically water only, and harmful exhaust gas is generated. It is an extremely efficient and clean power generation means, especially for polymer electrolyte fuel cells that use a fluororesin-based ion-exchange membrane as the electrolyte. R & D for higher efficiency power generation performance (high power generation performance), durability for long-term stable output (long-term durability), light weight, low cost, etc. Is being promoted.

 Until now, graphite materials have been mainly used as separators for such fuel cells. However, such graphite separators are not only expensive but also react to the separator side. When a gas flow path is formed, precise machining is required for graphite material, which is poor in toughness and brittle, which increases the processing cost, and also has poor impact resistance and vibration resistance. There was also a problem that recycling was difficult.

 In recent years, instead of such graphite separators,

Separator base made of Ni / SUS clad material, aluminum material made of aluminum or aluminum alloy, titanium material made of titanium or titanium alloy, stainless steel material, Ni-Fe alloy, etc. In addition, at least the noble metal such as gold (Au), silver (Ag), platinum (Pt), and palladium (Pd), silver, chromium nitride, platinum group composite oxide, or boron carbide and nickel Metal separator formed by plating a conductive film such as a material selected from the composite of 9

It has been proposed (for example, JP-A-10-228,914, JP-A-11-162,478, JP-A-2000-106,197, JP-A-2001-15,126, etc.).

 However, even in such Ni / SUS clad material separators and metal seolators, for example, Ni / SUS clad material separators have a large contact resistance with the electrode of the unit battery. In addition, there is a problem that the dissolved metal ions increase the membrane resistance of the electrolyte membrane and lower the battery output. In addition, metal separators have low Balta electric resistance, high airtightness and mechanical strength. Although it has the advantages of being able to reduce the processing cost due to having it, it is possible to make it thinner, it is easy to make it smaller and lighter, and if aluminum material is used, it is possible to make it even lighter. The metal of the material is susceptible to corrosion, especially in the case of aluminum material, which has a problem of corrosion that the corrosion rate is high. In addition, if the thickness of the conductive film is increased in order to solve the problem of corrosion, High cost Conversely, if the film thickness is reduced to reduce cost, pinholes or surface defects occur, making it difficult to solve the corrosion problem.

 Therefore, conventionally, in order to solve the above-mentioned various problems in the metal separator, for example, the electrode contact surface where the separator comes into contact with the electrode is partially plated with a thick gold plating by gold plating. Or a graded Au-Ni composition film in which the Au-Ni composition changes continuously due to electrical plating on the electrode contact surface where the separator comes into contact with the electrode (Japanese Patent Application Laid-Open No. 2001-345,109). (Japanese Patent Laid-Open No. 2001-357, 859) has been proposed.

However, the provision of a partially thick gold plating film in the former method has a problem that a masking step is required between the plating steps and the number of steps is increased, and the latter method is difficult. Providing a Ni-graded composition film has the problem that even if 1 ppm of Ni ion is eluted, battery performance will be degraded. It cannot always be said that the high power generation performance, long-term durability, light weight, and low cost, which are particularly required in applications such as power generation equipment for automobiles, can be simultaneously satisfied.

 Such problems are not limited to the above-described fuel cell separators, but include electrodes of unit cells constituting the fuel cell, electrodes of a primary battery of a portable device, electrode materials used in electrowinning and electroplating of metal, etc. The same is true in the field of use of a metal material having a corrosion-resistant conductive film formed on the surface of a metal substrate.

 Therefore, the present inventors have found that, for example, in the case of a noble metal element coating, the thickness of the noble metal element coating is 5 μm or less, which is much thinner than before, After conducting intensive studies on metal materials that can form a conductive film without surface defects and thereby solve both corrosion and cost problems, we will optimize the surface condition of the metal substrate Thus, the present invention has been completed.

In addition, the present inventors have developed a fuel cell that can simultaneously satisfy high power generation performance, long-term durability, light weight, and low cost, which are particularly useful for applications such as power generation devices for next-generation electric vehicles. Of fuel cell separators that are useful in the field. As a result of intensive studies to develop electrodes for unit cells, for example, in order to promote high power generation performance, light weight, and low cost as the material of the separator base material, After adopting an advantageous metal material and subjecting the separator base to etching treatment and a predetermined zinc substitution treatment, a precious metal stick treatment with a thickness of 0.01 to 1 m is performed, and at least the separator base material is used. thickness on the electrode contact surface 0 by. 0 1 ~ 1 μ m and that allowed to electrochemical polarization characteristics evaluation method form forming a polarization current 1 0 μ a / cm ² or less of the precious metal main luck film measured in a purpose Of the present invention Was completed.

Therefore, an object of the present invention is to optimize the surface condition of a metal substrate, Inexpensive and durable, for example, a noble metal element film with a thickness of 5 μm or less on the surface of the metal substrate is extremely thin compared to the past, and has a conductive film free of pinholes and surface defects. An object of the present invention is to provide a metal material having an excellent corrosion-resistant conductive film.

 Another object of the present invention is to provide a method for producing a metal material having such a corrosion-resistant conductive film.

 Further, another object of the present invention is to provide a fuel cell which can simultaneously achieve high power generation performance, long-term durability, light weight, and low cost, and which is suitable for use as a power generation device for a next-generation electric vehicle, for example. It is an object of the present invention to provide a metal separator for a fuel cell which is useful in production, and a metal material having a corrosion-resistant conductive film which can be used for an electrode of a unit cell constituting the fuel cell. Another object of the present invention is to provide a metal separator for a fuel cell, which is useful in manufacturing a fuel cell capable of simultaneously achieving high power generation performance, long-term durability, light weight, and low cost, and a fuel cell. An object of the present invention is to provide a method for producing a metal material having a corrosion-resistant conductive film that can be used for an electrode of a unit battery to be constituted. Disclosure of the invention

That is, the present invention is a metal material having a corrosion-resistant conductive film formed by forming a corrosion-resistant conductive film on the surface of a metal substrate formed of a metal material, and is observed on the surface of the metal substrate. The second phase compound of the metal substrate has a corrosion-resistant conductive film having a maximum length L of 5/6 times or less (L≤5X6T) the thickness T of the corrosion-resistant conductive film. It is a metal material. In addition, in the present invention, when producing a metal material having such a corrosion-resistant conductive film, a zinc immersion treatment of pickling and then immersing zinc in a metal substrate is repeated four times or more. A method for producing a metal material having a corrosion-resistant conductive film, wherein a corrosion-resistant conductive film is formed on the surface of the material. You.

The present invention also provides a metal substrate formed of a metal material, and a metal substrate formed on the surface of the metal substrate having a film thickness of 0.01 to 5 / im, and a method for evaluating electrochemical polarization characteristics. A metal material having a corrosion-resistant conductive film having a measured corrosion current of 10 μA / cm ² or less.

 Further, the present invention provides a metal substrate formed of a metal material, after the metal substrate is subjected to an etching process, a zinc substitution process of performing zinc immersion after pickling is repeated four times or more, and then the surface of the metal substrate is formed. This is a method for producing a metal material having a corrosion-resistant conductive film that forms a corrosion-resistant conductive film having a thickness of 0.11 to 5 μm.

 The metal material in the present invention can be used for, for example, a separator used when forming a fuel cell, an electrode of a unit cell constituting the fuel cell, and the like. When used for such a separator / electrode, the separator substrate constituting the separator and the electrode substrate constituting the electrode (the separator substrate and the electrode substrate are collectively referred to as “fuel cell forming material”). When forming, a metal substrate containing the second phase compound satisfying the above conditions may be used, or a metal substrate not restricted by the second phase compound may be used. When the metal material according to the present invention is used for applications other than a fuel cell, a corrosion-resistant conductive film that satisfies the conditions for the above-mentioned film thickness and polarization current may be formed. A corrosion-resistant conductive film that does not satisfy the current conditions may be formed.

 As described above, the metal material in the present invention can be used for a metal separator for a fuel cell, an electrode of a unit cell constituting the fuel cell, and the like. Hereinafter, the separator will be described as a specific example, but the same applies to the electrode of the unit battery except where specifically described.

Specifically, the metal material in the present invention includes a separator substrate formed of a metal material and at least a noble electrode contact surface of the separator substrate. A noble metal film formed by metal plating and having a film thickness of 0.01 to 1111, and a polarization current of 10 μA / cm ² or less measured by the electrochemical polarization characteristic evaluation method. It is a metal separator for a fuel cell having a luster film.

 Specifically, the method for producing a metal material according to the present invention includes forming a separator base material from a metal material, etching the separator base material, and immersing in zinc after pickling, followed by zinc substitution treatment four times or more. This is a method for producing a metal separator for a fuel cell, in which at least the electrode contact surface of the separator substrate is subjected to a noble metal plating treatment with a thickness of 0.01 to 1 μra.

 In the present invention, the metal base material constituting the metal material is, for example, a metal material such as an aluminum material made of aluminum or an aluminum alloy, a titanium material made of titanium or a titanium alloy, a stainless steel material, a Ni-Fe alloy material, or the like. It is preferably made of aluminum because of its low electric resistance and light weight. The aluminum material used for this purpose is not particularly limited. For example, various kinds of aluminum such as high-purity aluminum (JISH4170; 1N99), A1100, A5052, and A6063 can be used. Aluminum alloys can be mentioned.

Further, when the metal material of the present invention is used for a metal separator for a fuel cell, the metal material for forming a separator base material constituting such a separator is also, for example, aluminum or aluminum alloy made of aluminum alloy. Materials, titanium materials made of titanium or a titanium alloy, stainless steel materials, Ni-Fe alloy materials, etc., and aluminum materials, which are particularly excellent in workability, are preferred. The aluminum material is not particularly limited. For example, high-purity aluminum (JIS H4170; 1N99) or various aluminum alloys such as A1100, A5052, and A6063 are used. Can be mentioned. The second phase compound of the metal base means a substance (compound) that forms a phase with a substance other than the base metal in the metal base. Can be used to examine the size and distribution of reflected electrons using a scanning electron microscope (SEM), and to identify compounds by X-ray diffraction.

As the second phase compound of the metal base, specifically, for example, when the metal base is formed of aluminum material, a substance other than aluminum (A1) of the base metal ( Fe, Si, Cu, Mg, Zn and other impurities), for example, compounds such as Al ₃ Fe, a AlFeSi, Al ₃ Mg ₂ , Mg ₂ Si, and Al-Mg-Zn compounds. If the metal substrate is made of titanium, it contains substances other than titanium (Ti) (A1, Mn, Mo, Ta, Fe, Sn, Zr, and other impurities). For example, compounds such as Ti ₃ Al, TiMn, TiFe, and Ti ₃ Sn can be mentioned. Further, when the metal base is formed of stainless steel, a substance other than iron (Fe) of the material metal ( Cr, Ni, Mo, Nb, Ti, including C other impurities), for example _{FeCr, Cr 2 3 C 6,} Fe 3 C, MoC, Ru can and Ageruko compounds such as NbC

In the metal substrate used in the present invention, the maximum value L of the major axis L of the second phase compound of the metal substrate observed on the surface is 5/6 times or less the thickness T of the corrosion-resistant conductive film. (L 5/6 T), preferably 2/3 times or less (L ≤ 2/3 T), and the second phase compound on the surface of the metal substrate is a corrosion-resistant conductive film. The maximum value L of the major axis of the second phase compound, which is observed up to a depth of 5 μηι below the surface of the metal substrate, is the starting point for defects such as pinholes in the film. It is preferably no more than 5/6 times the thickness (L≤5Ζ6Τ), preferably no more than 2/3 times (L≤2 / 3 更 に), and more preferably on its surface. Preferably, the observed second phase compound of the metal substrate is substantially absent, and likewise, The second phase compound, which is observed up to a depth of 5 IX m below the surface of the metal substrate, should be substantially absent.

 Here, the above-mentioned maximum value L of the major axis of the second phase compound which is less than or equal to 5 Z 6 times (L ≤ 5/6 T) of the thickness T of the corrosion-resistant conductive film is, for example, a metal. When the thickness of the corrosion-resistant conductive film formed on the surface of the base material is 1.2 or im, the maximum value L of the major axis of the second phase compound observed on the surface of the metal base material is 1. 1. μιη or less, and in the present invention, when the corrosion-resistant conductive film is a noble metal element film, the target of the film thickness is διη or less, and as a result, it is observed on the surface of the metal substrate. The maximum value L of the major axis of the second phase compound must also be 4.2 μm or less. If the maximum value L of the major axis of the second phase compound observed on the surface of the metal substrate exceeds 5/6 times the thickness of the corrosion-resistant conductive film, the second phase compound becomes It becomes a starting point for defects such as pinholes, and as a result, surface defects such as pinholes occur.

Further, a second phase compound of the metal substrate to be above observations substantially absent, the second phase when the microscope observation range of 1 mm ² in 1 0 0 0 times magnification In the sense that the compound cannot be seen with the naked eye, this means that the major diameter of the second phase compound is substantially equal to 0.05 μππ, and the second phase compound below this can be ignored. I do.

In the present invention, when the second phase compound is observed on the surface of the metal substrate, the number of the second phase compound is preferably 20 / mm ² or less, and more preferably. Or 10 or less per mm ² . If the number of the second phase compounds observed on the surface of the metal substrate exceeds 20 / mm ² , the adhesion of the corrosion-resistant conductive film is insufficient, and the film in the relevant portion is easily lifted.

In the present invention, when the metal substrate is an aluminum material, its chemical composition is preferably magnesium (Mg) of less than 7% by mass, Less than 3% by mass of zinc (Zn), less than 0.01% by mass of silicon (Si), less than 0.01% by mass of iron (Fe), and 0.01% by mass of copper (Cu). /. And the balance is preferably aluminum (A1) and unavoidable impurity elements. This is because, when rolling slabs are manufactured by the normal DC (direct chilling) method, the solidification rate during fabrication is high and solidification occurs in a non-equilibrium state, so unavoidable impurities are forcibly dissolved. However, if the content of the above Mg, Zn, Si, Fe, and Cu exceeds the above regulation value, it may crystallize as a coarse second phase compound.

 In addition, when the metal material according to the present invention is used for a metal separator for a fuel cell, the separator substrate made of a metal material may have a reaction gas flow path formed on an electrode contact surface thereof. Although the reaction gas flow path may not be formed, the separator base material is formed of a metal material, so that precise machining is easy and the processing cost is low. In consideration of the manufacturing cost of the entire fuel cell, it is preferable that the separator substrate be a reaction gas flow path formed on the electrode contact surface thereof.

 In the case where the metal material of the present invention is used as an electrode of a unit cell used in the construction of a fuel cell, a reaction gas flow path is formed on the electrolyte side of the unit battery for the electrode substrate formed of the metal material. It is good to have

In the present invention, the corrosion-resistant conductive film formed on the surface of the metal substrate is preferably gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium ( Examples include a metal element film, a nickel film, and a copper film formed using Rh), ruthenium (Ru), or an alloy of these noble metals. The method for forming such a corrosion-resistant conductive film is not particularly limited, and includes various methods such as sputtering and plating. From the viewpoint of the presence or absence of a gas step, it is preferably a plating method.

 In addition, when the corrosion-resistant conductive film formed on the surface of the metal substrate is a noble metal plating film formed by a noble metal plating process, particularly, a separator substrate for forming a metal separator for a fuel cell is used. In the case of a noble metal plating film formed on the surface of a metal, the noble metal plating film formed on the surface of such a metal separator base is made of gold (Au), silver (Ag), or platinum (Pt). , Palladium (Pd), rhodium (Rh), luteuium (Ru), or precious metal plating films formed using alloys of these precious metals. From the viewpoint of being extremely stable, it is preferably a gold-mesh coating. The noble metal plating film may be formed on at least the electrode contact surface of the separator substrate, but is preferably used from the viewpoint of maintaining long-term durability and simplifying the manufacturing process. It is good to be formed on the whole surface. In the case of an electrode substrate for forming an electrode constituting a unit battery, it is preferable that the above-mentioned noble metal plating film is formed on the surface of the electrolyte constituting the unit battery.

When the corrosion-resistant conductive film is a noble metal element film, it differs depending on the use of the metal material, the type of metal forming the film, and the like, but is usually 0.01 μlη or more. It is preferably 5 μm or less, more preferably 0.05 μm or more and 5 m or less. If the thickness is less than 0.1 μππι, pinholes are likely to occur even on the surface where no second-phase compound is present. Conversely, if the thickness is greater than 5 Xm, the corrosion resistance will increase. Does not change, but it is difficult to achieve cost reduction. This corrosion-resistant conductive film must be completely defect-free with no pinholes or surface defects. If any pinholes or surface defects exist, corrosion starts from these pinholes and surface defects. As a result, the problem of peeling of the film occurs. The corrosion-resistant conductive film preferably has a thickness of 0.01 to 5 μm and a polarization current measured by an electrochemical polarization characteristic evaluation method of 10 μAra / cm ² or less. In the case where the corrosion-resistant conductive film is a noble metal plating film formed by a noble metal plating process, in particular, the noble metal formed on the surface of a separator substrate for forming a metal separator for a fuel cell. In the case of a plating film, the thickness of the noble metal plating film formed on the surface of the separator substrate is from 0.01 / im to 1 / zm, preferably from 0.05 μιη to 0. The polarization current is preferably 5 μιη or less, and the polarization current measured by the electrochemical polarization property evaluation method is 10 μA / cm ² or less, preferably 7 μA / cm ² or less. Good. Regarding the film thickness, if it is thinner than 0.01 βm, there is a problem that pinholes are likely to occur.On the other hand, if it is thicker than 1 μm, it is possible to achieve low cost. It becomes difficult. If the polarization current is higher than 10 μA / cm ² , the obtained noble metal plating film may not be completely defect-free without pinholes. The noble metal plating film must be completely defect-free with no pinholes or surface defects. If any pinholes or surface defects exist, corrosion starts from these pinholes or surface defects, and the battery output A problem of performance degradation occurs.

Here, the method of measuring the polarization current is the force performed by the electrochemical polarization characteristic evaluation method, and the specific method is as follows. That is, for example, a sample is placed in an electrolyte solution such as an aqueous acetic acid solution so as to face a platinum counter electrode, and a silver-silver chloride electrode is used as a reference electrode. Immerse in an aqueous solution, connect a saturated potassium chloride aqueous solution and the sample with a salt bridge, connect the sample, platinum counter electrode, and silver-silver chloride electrode to a potentiostat, and apply the sample potential to the silver-silver chloride electrode. On the other hand, when scanning from the natural electrode potential to the oxygen generation potential toward the anode, the peak current flowing through the sample electrode is measured as the polarization current. In the present invention, when producing a metal material having a corrosion-resistant conductive film, first, the maximum value B of the major axis of the second phase compound observed on the surface is as small as possible, or It is preferred to prepare a metal substrate that is substantially free of the observed second phase compound.

 Methods for producing such a metal substrate include, for example, dissolving a high-purity aluminum base metal, adding an alloy element as necessary, adjusting the components, and then forming an aluminum alloy having a desired component composition. After the alloy is melted and further DC-formed to produce an ingot, it is rolled to a predetermined thickness by hot rolling and cold rolling, and further annealed under controlled conditions, if necessary. For example, a method of performing a grinding process (for example, see Japanese Patent Application Laid-Open No. 9-235,640; see Japanese Patent Application Laid-Open No. 4-341,536).

 In the present invention, the maximum value of the major axis L of the second phase compound of the metal substrate, which is observed on the surface of the metal substrate, is set to 1 It is preferable to form a corrosion-resistant conductive film having a film thickness T of 2 times or more, preferably 1. 5 times or more, preferably, a surface polishing treatment prior to forming a corrosion-resistant conductive film. It is preferable to perform a zinc immersion treatment in which zinc is immersed after etching, pickling and the like.

 In the surface polishing treatment performed for this purpose, the surface roughness {JIS B 0601 (2001)} is preferably 0.02 to 0.3; um, more preferably 0.03 to 0.2. it is better to adjust to the range of m. If the surface roughness of the metal substrate at this time is greater than 0.3 zm, pinholes and surface defects are likely to occur in the formed corrosion-resistant conductive film due to recesses on the surface of the metal substrate. As a result, the corrosion resistance is reduced, and if the corrosion resistance is smaller than 0.02 μm, the adhesion between the formed corrosion-resistant conductive film and the surface of the metal substrate is reduced, and In some cases, the peeling of the film occurs locally when the used metal material is used.

Here, the surface roughness of the metal substrate is expressed in the range of 0.02 to 0. The method for the surface polishing treatment is not particularly limited, but usually, a method such as electrolytic polishing, mechanical polishing, puff polishing, blast polishing, barrel polishing, or the like is employed, preferably electrolytic polishing. Processing. The surface polishing treatment of the metal base material may be performed using only one of the above-described processing methods in consideration of the material of the metal base material or the like, or may be performed in combination of two or more processing methods.

 In addition, the above-mentioned etching treatment is usually performed by immersing the degreased metal base material in an etching treatment liquid. The etching solution used for this purpose is usually an aqueous solution of sodium hydroxide such as sodium hydroxide, potassium hydroxide, sodium carbonate, or sulfuric acid-phosphoric acid. An aqueous acid solution such as a mixed aqueous solution is used. When an aqueous alkaline solution is used, its concentration is 20 g / L or more and 200 g / L or less, preferably 50 g / L or more and 150 g / L or less. Usually, the immersion temperature is from 30 ° C to 70 ° C, preferably from 40 ° C to 60 ° C, and the immersion time is from 0.5 minutes to 5 minutes. Preferably, it is 1 minute or more and 3 minutes or less. When a sulfuric acid-phosphoric acid mixed aqueous solution is used as the acid aqueous solution, the concentration of the sulfuric acid is 10 g / L or more and 500 g / L or less, preferably 30 g / L or more. Phosphoric acid concentration of 10 g / L or more at 0 g / L or less

120 g / L or less, preferably 30 g / L or more and 500 g / L or less, and the immersion temperature is usually 30 ° C or more and 110 ° C as the processing conditions. C or less, preferably 55 ° C or more and 75 ° C or less, and immersion time of 0.5 minutes or more

15 minutes or less, preferably 1 minute or more and 6 minutes or less.

 Further, in the above zinc substitution treatment, in the pickling step, the pickling bath is an acid such as nitric acid, sulfuric acid, hydrochloric acid, etc., and the concentration is 5 wt ° /. More than 5

O wt. /. An aqueous acid solution of the following, preferably an acid aqueous solution having an acid concentration of 10 wt% / _{0 to} 40 wt%, more preferably nitric acid having a concentration of 25 to 30 wt%. Using an aqueous solution, the immersion temperature is 15 ° C or more and 30 ° C or less, The immersion time is preferably from 20 ° C to 25 ° C, and the immersion time is preferably from 5 seconds to 120 seconds, preferably from 15 seconds to 60 seconds. By performing pickling under such conditions using such a pickling bath, the substituted zinc layer can be effectively removed.

 Also, in the zinc immersion step of the zinc substitution treatment, the zinc immersion bath has a zinc oxide concentration of 1.5 g / L or more and 60 g / L or less, preferably 3.5 g / L or more and 50 g or more. / L or less, and the alkaline concentration of alkaline such as sodium hydroxide and hydroxylating bead 40 g / L or more and 400 g / L or less, preferably 80 g / L Use an aqueous zinc oxide solution of L to 200 g / L and an immersion temperature of 15 to 30 ° C, preferably 20 to 25 ° C. The immersion time is preferably 5 seconds or more and 120 seconds or less, more preferably 15 seconds or more and 50 seconds or less. If the zinc oxide concentration in the zinc immersion bath is lower than 1.5 g / L, there is a problem that the substituted zinc layer becomes non-uniform.On the other hand, if the zinc oxide concentration is higher than 60 g / L, the gold plating film will There is a problem of non-uniformity, and if the alkali concentration is lower than 40 g / L, there is a problem that the adhesion of the substituted zinc layer is reduced, and conversely, it is higher than 400 g / L. This causes a problem that the surface roughness of the metal substrate increases.

 In the present invention, the zinc substitution treatment of immersing in zinc after the above pickling is preferably repeated at least four times or more. If this zinc substitution treatment is performed up to three times, pinholes and surface defects may occur in the corrosion-resistant conductive film, and a completely defect-free noble metal plating film without pinholes and surface defects may be formed. And it becomes difficult.

 In this way, the surface of the metal substrate is polished, then subjected to an etching process, and further subjected to zinc substitution treatment four times or more. To form a corrosion-resistant conductive film having a thickness of 0.01 to 5 m.

Regarding the method of forming this corrosion-resistant conductive film, a plating treatment die Although a method such as a putting treatment can be used, preferably, a plating treatment is used. For example, an electroless plating (Me-ELP), a substitution plating (Me-SP), an electrolytic plating ( A plating treatment method such as Me-EP) or electrolytic strike plating (Me-EPS) can be used, and a plating bath having the same bath composition as the conventional plating bath can be used. In addition, the same processing conditions as in the past can be used for this plating process, and the processing conditions vary depending on the type of plating metal used. The temperature is about 50 to 75 ° C, and the current density is about 0.1 to 0.5 A / dm ² .

 According to the above-described method of the present invention, a completely defect-free corrosion-resistant conductive film having no pinholes and no surface defects is formed on the surface of a metal substrate, although the film is as thin as possible. Therefore, even when an expensive precious metal corrosion-resistant conductive film is formed, its thickness can be reduced as much as possible, and it is inexpensive and has excellent durability. Metal materials with a corrosion-resistant conductive film useful in many applications, such as electrodes for unit cells constituting fuel cells, electrodes for primary batteries of mobile devices, and electrode materials used in electrowinning and electroplating of metals Can be easily manufactured.

In addition, a metal material having a corrosion-resistant conductive film having a thickness of 0.01 to 5 μm as described above and a polarization current of 10 μA / cm ² or less measured by an electrochemical polarization property evaluation method is manufactured. In particular, when manufacturing a metal separator with a film thickness of 0.01 to 1 μm and a polarization current of 10 μA / cm ² or less measured by the electrochemical polarization characteristic evaluation method, First, a separator substrate is formed from a metal material, and after the separator substrate is subjected to an etching treatment, a zinc substitution treatment of pickling and immersing in zinc is repeated four times or more. Perform precious metal plating treatment of ~ 1 μιη.

Here, the etching of the separator substrate is usually performed by a degreasing treatment. This is performed by immersing the separated separator substrate in an etching solution. The etching solution used for this purpose is usually an aqueous solution of sodium hydroxide, such as sodium hydroxide, sodium hydroxide or sodium carbonate, or a mixture of sulfuric acid and phosphoric acid. An aqueous acid solution such as an aqueous solution is used. In the case of using an aqueous alkaline solution, its concentration is from 20 g / L to 200 g / L, preferably from 5 Og / L to 15 Og / L. Usually, the immersion temperature is 30 ° C to 70 ° C, preferably 40 ° C to 60 ° C, and the immersion time is 0.5 minutes to 5 minutes. It is preferably 1 minute or more and 3 minutes or less. When a sulfuric acid-phosphoric acid mixed aqueous solution is used as the acid aqueous solution, the concentration of the sulfuric acid is 10 g / L or more and 500 g / L or less, preferably 30 g / L or more. At a concentration of 300 g / L or less, the concentration of phosphoric acid is 10 g / L or more and 1200 g / L or less, preferably 30 g / L or more and 500 g / L or less. Generally, the immersion temperature is 30 ° C or more and 110 ° C or less, preferably 55 ° C or more and 75 ° C or less, and the immersion time is 0.5 minute or more and 15 minutes or less. It is preferably 1 minute or more and 6 minutes or less.

After the etching treatment, a zinc substitution treatment is performed. In the pickling step of the zinc substitution treatment, the acid is a nitric acid, a sulfuric acid, a hydrochloric acid, or the like, and the concentration is 5 wt% or more. An aqueous acid solution of 50 or less, preferably an acid aqueous solution having an acid concentration of 10 wt% or more and 40 wt% or less, more preferably a nitric acid solution of 25 wt% or more and 30 wt% or less. Using an aqueous solution, the immersion temperature is 15 ° C or more and 30 ° C or less, preferably ²⁰ ° C or more and 25 ° C or less, and the immersion time is 5 seconds or more and 120 seconds or less, preferably It is better to do it for 15 seconds or more and 60 seconds or less. By performing pickling under such conditions using such a pickling bath, the substituted zinc layer can be effectively removed.

Furthermore, in the zinc immersion step of the zinc substitution treatment, the zinc immersion bath is provided with a zinc oxide concentration of 1.5 g / L or more and 60 g / L or less, preferably 3.5 g / L or less. 50 g / L or less, and alkaline concentration of alkaline such as sodium hydroxide and potassium hydroxide 40 g / L or more and 400 g / L or less, preferably Use an aqueous zinc oxide solution of 80 g / L or more and 200 g / L or less, and immersion temperature of 15 ° (30 ° 以上 or more, preferably 20 ° C or more and 25 ° C or less) The immersion time should be 5 seconds or more and 120 seconds or less, preferably 15 seconds or more and 50 seconds or less.The zinc oxide concentration in the zinc immersion bath should be 1.5 g / L. If it is too low, the substituted zinc layer will be non-uniform. Conversely, if it is higher than 60 g / L, if the gold plating film becomes non-uniform, there will be problems with the re-emission and the alkali concentration If it is lower than 400 g / L, the adhesion of the substituted zinc layer will be reduced.On the other hand, if it is higher than 400 g / L, the roughness of the aluminum surface will increase. Occurs.

In the present invention for producing a metal material having a corrosion-resistant conductive film having a film thickness of 0.01 to 5 m and a polarization current of 10 μA / cm ² or less measured by the electrochemical polarization characteristic evaluation method, thickness 0.0 1 when manufacturing the polarization current 1 0 μ Α / cm ² or less of metallic separator made measured in l / zm and electrical chemical polarization characteristic evaluation method, zinc after said pickling It is preferable to repeat the zinc substitution treatment for immersion at least four times or more. When the zinc substitution treatment is performed up to three times, when the number of pinholes generated in the noble metal plating film is measured, it depends on the thickness of the noble metal plating film. It is difficult to form a completely defect-free noble metal plating film without pinholes or surface defects.

The separator substrate is etched in this way, and then zinc-substituted four or more times, followed by a noble metal plating process with a thickness of 0.01 to 1 μm. This noble metal plating treatment includes, for example, electroless plating (Me-ELP), substitution plating (Me-SP), electrolytic plating (Me-EP), electrolytic strip plating (Me-EPS), etc. The method of masking can be mentioned. In addition, the plating bath having the same bath composition as the conventional bath can be used. The processing conditions for the precious metal plating process can be the same as those used in the past, and vary depending on the type of noble metal used. The current density is about 0.1 to 0.5 A / dm ^{2 at} about 0 to 75 ° C.

In addition, a metal material having a corrosion-resistant conductive film having a thickness of 0.01 to 5 μm and a polarization current of 10 μA / cm ² or less measured by an electrochemical polarization characteristic evaluation method is manufactured. The method of the present invention is particularly necessary when manufacturing a metal separator having a film thickness of 0.1 to 1 μm and a polarization current of 10 nA / cm ² or less measured by an electrochemical polarization characteristic evaluation method. The surface of the separator base material before the etching treatment is subjected to a polishing treatment to obtain a surface roughness of {JIS B 0601 (2001)}, preferably from 0.02 to 0.3 μππι, more preferably. Should be adjusted in the range of 0.03 to 0.2 / xra. If the surface roughness of the separator substrate before this etching treatment is larger than 0.3 μm, pinholes and surface defects may occur in the formed conductive film due to the concave portions on the surface of the separator substrate. When the thickness is smaller than 0.02 μm, the adhesion between the formed conductive film and the surface of the separator substrate is reduced. When the separator comes into contact with the battery electrode when using the separator, film peeling may occur locally.

Here, regarding the method for polishing the surface of the separator base material before the etching treatment to the range of 0.02 to 0.3 μηι, the surface roughness is set to the range of 0.02 to 0.3. The method is not particularly limited as long as the method can be adjusted to a range of μm, but usually, methods such as electrolytic polishing, mechanical polishing, buff polishing, plastic polishing, barrel polishing, etc. are employed, and preferably, electrolytic polishing is performed. It is. The surface polishing treatment of the separator base material In consideration of the material of the substrate, etc., the treatment may be performed using only one of the above-described treatment methods, or may be performed using a combination of two or more treatment methods. According to the above-described method of the present invention, electrochemical polarization property evaluation is performed on a surface of a separator substrate formed of a metal material and a surface defect of an electrode substrate that cannot be detected by a normal pinhole detection method. It is possible to form a thin and defect-free noble metal plating film as much as possible by detecting the polarization current by the polarization method. Combined with excellent performance, it is possible to manufacture a metal separator / unit cell electrode that can simultaneously satisfy the high power generation performance, long-term durability, light weight, and low cost of a fuel cell. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, preferred embodiments of the present invention will be specifically described based on experimental examples, examples, and comparative examples.

 Experimental example 1

 [Preparation of aluminum base material]

 After dissolving aluminum (1N99) and dissolving additional elements, DC was manufactured to produce aluminum slabs (slab lumps). Next, the aluminum ingot was soaked at 300 to 550 ° C., hot-rolled, and then cold-rolled to prepare a 5.5 mm-thick aluminum plate. This aluminum plate is cut into a size of 100 mm X 100 mm, and is subjected to grinding with a grinding wheel to obtain a size of 5 mm X 100 mm X 100 ram. An aluminum substrate was prepared.

For Aruminiumu substrate obtained Te this good Unishi, the results of the second phase compounds observed was observed using reflected electron image of SEM on the surface, the second phase compounds eight / ² is observed, Maximum value of the major axis (Table The maximum value of the major axis of the second phase compound on the surface) L was 2.5. For the second phase compound in the depth direction, the aluminum substrate was immersed in a 50 g / L sodium hydroxide aqueous solution at a temperature of 50 ° C, and stepwise etched. Examination of the maximum value of the major axis of the second phase compound at a depth of 5 μm below the surface revealed that the maximum value was 3. Ομπι. (Preparation of aluminum separator for fuel cell) ''

 Reactor gas channels having a depth of 0.8 mm and a width of 0.8 mm were formed on both sides of each of the 5 mm-thick aluminum base materials obtained above by press caulking, and In a degreasing bath having a composition of 25 g / L sodium, 25 g / L sodium carbonate, 25 g / L sodium phosphate, and 1.5 g / L surfactant. After degreased at 60 ° C and a immersion time of 5 minutes, rinsed with water, and then immersed in 50 g / sodium hydroxide solution as an etching solution at 50 ° C. Etching was performed under the conditions of 3 minutes and immersion time.

The etched aluminum base material obtained in this manner is 30wt /. -Use nitric acid aqueous solution as pickling bath, add sodium hydroxide 100 g / L, zinc oxide 50 g / L, ferric chloride 1 g / L, and mouth shell salt 10 g / L Using a zinc immersion bath having the following composition, the zinc substitution treatment of immersing for 30 seconds at room temperature and then immersing in zinc for 30 seconds at room temperature is performed four times, followed by electrolytic gold plating bath ( Te "click, using a 'service Co. Auruna 59 1), the temperature 5 0 ° C, current density 0.5 by controlling the a / dm ² and gold precipitation amount 2 mg / coulomb condition in processing time Electrolytic gold plating was performed, and the ratio (T / L) between the thickness T of the electrolytic gold plating skin and the maximum value L of the major axis of the second phase compound was 0.5, 1.0, and 1 respectively. Prototypes of five types of aluminum separators, 2, 1.5 and 2.0, were produced.

In addition, for the same four-time zinc-substituted separator substrate as above, the temperature was raised to 70 ° C using an electrolytic silver plating bath (Te, Kalsa Alta, Alna CF). Current density 5 0 A / dm performed in electrolytic Ginme luck process ² conditions, electrolytic Ginme Tsu ratio of the maximum value L of the major axis of the thickness T and the second phase compounds of key film (T / L) pixels Prototypes of five types of aluminum separators, 0.5, 1.0, 1.2, 1.5 and 2.0, respectively, were produced.

Furthermore, for the same four times as above, the zinc-substituted separator substrate was heated to a temperature of 40 ° C and a current density of 40 ° C by using an electrolytic platinum plating bath (Te, K-Sulfur® K). 1. performs electrolytic platinum main Tsu key process in the conditions of OA / dm ^2, the ratio between the maximum value L of the major axis of the thickness T and the second phase compounds of the electrolytic white gold-edge tool key film

Prototypes of five types of aluminum separators with (T / L) of 0.5, 1.0, 1.2, 1.5 and 2.0 were prepared.

 [Measurement of film pinhole number]

Each prototype separator thus produced was immersed in a 20 g / L aqueous solution of copper sulfate at room temperature for 5 minutes, the copper deposition was counted, and the number of pinholes (pcs / cm) was measured. ² ) was measured.

 Table 1 shows the results.

table 1

Number of pinholes (pcs / cm ² )

In addition, for each of the above separator prototypes, an aqueous acetic acid solution of pH 3 was used as the test solution, a silver-silver chloride electrode was used as the reference electrode, and the scanning potential was 0 to: L 0 OmV vs Ag / AgClCl. The polarization current (/ A / cm ² ) was measured by the electrochemical polarization characteristic evaluation method.

Table 2 shows the results. Table 2

Polarization current (μA / cm ² )

In addition, for each of the separator prototypes above, a unit battery was assembled using the membrane electrode assembly, hydrogen gas and air were supplied to the reaction gas flow path of the separator prototype, and a battery power generation test was performed continuously. The time during which the battery electromotive force of the battery was 10% lower than the electromotive force at the start of power generation was measured and defined as the separator life (hrs.).

 Table 3 shows the results.

Table 3

 Separator life (hrs.)

According to Experimental Example 1, as is clear from the results in Table 1, the thickness T of the plating film and the maximum value L of the major axis L of the second phase compound observed on the surface of the aluminum-base material were determined. When the ratio (T / L) is 1.2 or more, pinholes in the plating film are no longer observed, and the polarization current shown in Table 2 indicates that the TZL value is almost completely saturated when the TZL value is 1.2 or more. In addition, a defect-free paint film having no surface defects was obtained.Furthermore, the separator life shown in Table 3 shows that when the TZL value was 1.2 or more, it reached 30000 hours or more. It was found that the performance as a Lumi separator was fully exploited.

 Examples 1 to 12 and Comparative Examples 1 to 4

In the same manner as in Experimental Example 1 above, an aluminum substrate was prepared in which the maximum length L of the second phase compound on the surface and the maximum length L of the second phase compound up to 5 μra below the surface had the values shown in Table 4. Then, apply the noble metal plating treatment shown in Table 4 to determine the thickness T of the noble metal plating film and the maximum major axis length L of the second phase compound on the surface or the maximum major axis length of the second phase compound up to 5 μm below the surface. A prototype of an aluminum separator was produced in the same manner as in Experimental Example 1 except that a noble metal plating film having a ratio to L (T / L) was formed. Polarization current (μA / cm ² ) and separator life (hrs.) Were measured for each of the obtained separator prototypes in the same manner as in Experimental Example 1, and the results are shown in Table 4.

Aluminum base material T / L

 Precious metal plating

 L s value Lu value processing (* 4) and membrane flow

 Ύ / Ls Ύ / Lu

 (* 2) (μm) (* 3) (μm) Thickness T m) μA / cm-

^ n s.

1N99 2.5 3.0 All 1.4 1.π

9 3wt% Mg A 丄 2.7 3.0 1.1.1 υυ u owt oMg ~ 0.3wt% Zn-AJL 2.7 7 ，， － / 1. 1.y u u u

4 丄 iy U Τ7Γ 丄, \ 0

 Real 5 丄 J y y U U / «_> 丄.

 o

 6 1W99 2. 5 3.0 r Q / ο. 1. 1. I 0 \ A un un u

 7 丄 wyy b b 0. U η /. 丄 丄 乙 \ nn n

CO Example 8 1N99 2.5 3.0 U iir / Ό 1.4 1.2 \ D \, π UΠU ΠU

 9 1N99 2.5 3.0 Ir-EP / 3.6 1.4 1.2g 6> 3 000

10 1N99 2.5 3.0 Au, Ag-ELP / 3. 6 1.4 1.2 <6〉 3,000

11 1N99 2.5 3.0 Au-EP / 4. 5 1.8 1.5 <6> 3,000

12 1N99 2.5 3.0 Au-EP / 5.0 2.0 1.7 1.7 6> 3,000

1 1N99 2.5 3.0 Au-EP / 2.5 1.0 0.8 170 1,050 ratio

 2 3wt% Mg-Al 2.7 3.0 Au-EP / 3.01.1.10 580 50

 Three

 Example 1N99 2.5 3.0 Ag-ELP / 2.5-1.0 0.8 180 900

 4 1N99 2.5 3.0 Au-EP / 1.0 0.4 0.3 0.3565 80

(Note) * 1: High purity aluminum (1N99) 3wt ° /. Aluminum containing Mg (3wtMg-Al)

 3wt g & 0.3wt% Zri containing anoremium (3wt Mg-0.3wt Zn-Al)

 * 2: Maximum value of the major axis of the second phase compound on the surface (Ls value)

 * 3: Maximum value of the major axis of the second phase compound up to 5 m below the surface (Lu value)

 * 4: Electrolytic noble metal plating (Me_EP), electroless precious metal plating (Me-ELP)

04 Further, a preferred embodiment of the present invention was specifically described based on another experimental example in which an aluminum separator was experimentally manufactured using an aluminum material as a metal material and the obtained separator prototype was used. Will be described.

 Experiment 2 ''

 A 5 mm thick aluminum substrate (1N99) is used to cut out a separator base material of size 5111 [11 s 100 111 1 111 s 100 mm], and both sides of this separator base are pressed by pressing. Reactant gas channels having a depth of 0.8 mm and a width of 0.8 mm were formed respectively, and then sodium hydroxide 25 g / L, sodium carbonate 25 g / L, and sodium phosphate After degreasing in a degreasing bath with a composition of 25 g of lithium and 1.5 g / L of surfactant at an immersion temperature of 60 ° C and an immersion time of 5 minutes, and then washing with water, Etching was performed using a 50 g / L aqueous solution of sodium hydroxide as an etching solution at an immersion temperature of 50 ° C and an immersion time of 3 minutes.

With respect to the thus-etched separator base material thus obtained, a 30 wt% aqueous solution of nitric acid was used as an pickling bath, sodium hydroxide 100 g / L, zinc oxide 50 g / L. Using a zinc immersion bath having a composition of 1 g / L of ferric chloride and 1 Og / L of Rochelle salt, immerse for 30 seconds at room temperature. 1 to 6 times (zinc replacement times: 1 to 6 times), followed by 10 g / L of potassium cyanide and 30 g / L of potassium cyanide. Using a gold plating bath having a composition of 30 g / L of carbon dioxide roll and 30 g / L of potassium phosphate, the bath temperature was 55 ° C and the current density was 0.5 A / dm. ^The electroless gold plating was performed by controlling the processing time under the conditions of ² , and the thickness of the separator base material at each number of zinc substitution treatments was 0.01 m, 0.1 βία and 0.1 1. A prototype of an aluminum separator with a μηι gold film was fabricated.

For each separator prototype manufactured in this way, copper sulfate 2 It was immersed in a 0 g / L aqueous solution at room temperature for 5 minutes, the copper deposition was counted, and the number of pinholes was measured.

 Table 5 shows the results.

Table 5

In addition, for each of the above separator prototypes, an aqueous acetic acid solution of pH 3 was used as a test solution, a silver-silver chloride electrode was used as a reference electrode, and the scanning potential was 0 to; For l, the polarization current was measured by the electrochemical polarization property evaluation method.

 Table 6 shows the results.

Table 6

Furthermore, for each of the separator prototypes above, a unit battery was assembled using a membrane electrode assembly (manufactured by Japangotechs Co., Ltd.), and hydrogen gas and air were supplied to the reaction gas flow path of the separator prototype to produce a battery power generation test. To The battery electromotive force during this power generation test was measured. Table 7 shows the results.

Table 7

Furthermore, for each of the separator prototypes, a unit battery was assembled using the membrane electrode assembly described above, and hydrogen gas and air were supplied to the reaction gas flow path of the separator prototype, and a battery power generation test was continuously performed. The time during which the battery electromotive force at the time of the power generation test decreased by 10% compared to the electromotive force at the start of power generation was measured and defined as the separator life.

 Table 8 shows the results.

Table 8

According to Experimental Example 2, the number of pinholes generated by the number of zinc substitution treatments increased by one, two, and three times from the results in Table 5 was dramatically reduced. The replacement process still has several pinholes It was found that gold plating films with no pinholes were obtained after four or more zinc substitution treatments. Looking at the polarization current shown in Table 6, the polarization current was 100 nA / cm ² or more in the three zinc substitution treatments, but was almost completely saturated in the four or more zinc substitution treatments. As a result, a defect-free gold plating film having no surface defects is obtained. Also, looking at the battery electromotive force shown in Table 7 and the separator life shown in Table 8, three zinc substitution treatments were still not completely satisfactory, but four or more zinc substitution treatments were not enough. It was found that it was completely saturated by the treatment, and the performance as an aluminum separator was sufficiently brought out. Experiment 3

 Using the aluminum material shown in Table 9, two, three, or four zinc replacement treatments were performed, and the noble metal plating treatment shown in Table 9 was performed to apply the film thickness shown in Table 9 to the surface of the separator base material. A prototype of an aluminum separator was produced in the same manner as in Experimental Example 2 except that the noble metal plating film was formed.

 The polarization current and the battery electromotive force of each of the obtained separator prototypes were measured in the same manner as in Experimental Example 2 above.

Table 9 shows the results.

 Aluminum containing 5wt% Mg (5wt% Mg'Al)

 * 2: Electroless noble metal plating (Me-ELP), substituted noble metal plating (Me-SP),

Electrolytic precious metal plating (Me-EP), electrolytic precious metal plating (Me-EPS) Experiment 4

 Using the aluminum material shown in Table 10, the degreasing-treated separator substrate obtained in the same manner as in Experimental Example 2 was subjected to a surface polishing treatment by the following method before the etching treatment, and then As in Experimental Example 2, an aluminum separator having a 0.1-meter-thick gold plating film on the surface was subjected to etching treatment, four zinc substitution treatments, and gold plating treatment shown in Table 10. Prototype was made.

 (Electropolishing)

 Using an electropolishing bath of 220 ml / L perchloric acid and 780 ml / L acetic anhydride, immerse the degreased separator substrate in this electrolytic polishing bath, and use this separator substrate as the anode. The current density is determined by using a platinum plate as the cathode.

Electropolishing treatment was performed for 5 minutes under the condition of 1 OA / dm ² , followed by washing with water and drying.

 [Chemical polishing]

 Phosphoric acid 75. /. , Nitric acid .20. /. And water5. /. It was immersed in a chemical polishing bath having the following composition at 90 ° C. for 5 minutes, then washed with water and dried.

 (Puff polishing)

 A cotton buff was used as a puff, and alumina fine powder (particle size: P2500) was used as an abrasive.

 (Blast polishing)

A mixture of fine glass beads (particle size FOO) was sprayed at an air pressure of 2 kg / cra ² , washed with water after polishing, and dried.

 (Mechanical polishing)

 After polishing using # 600 emery polishing paper, final polishing was again performed using # 250 emery polishing paper, followed by washing with water and drying.

Separation after surface polishing treatment for each of the obtained separator prototypes In addition to measuring the surface roughness of the base material, the polarization current, the battery electromotive force, and the separator life were measured in the same manner as in Experimental Example 2 above.

 The results are shown in Table 10.

Table 10

 (Note) * 1: High purity aluminum (1N99), aluminum containing 3wt% Mg (3wt% Mg-Al), aluminum containing 5wt% Mg (5wt% Mg-Al)

* 2: Electrolytic gold plating (ΑιτΕΡ), electroless gold plating (Au • ELP)

Industrial applicability

 According to the present invention, the surface state of the metal substrate is optimized, and the thickness of the precious metal element film on the surface of the metal substrate is, for example, 5 μm or less, which is much thinner than the conventional one, It is possible to provide a metal material having an inexpensive and highly durable corrosion-resistant conductive film formed with a conductive film free of defects and surface defects.

 In addition, the metal separator for a fuel cell obtained by the present invention can simultaneously achieve high power generation performance, long-term durability, light weight, and low cost. It is extremely useful in producing suitable fuel cells.

Claims

Range of request

(1) A metal material having a corrosion-resistant conductive film formed by forming a corrosion-resistant conductive film on the surface of a metal substrate formed of a metal material, wherein the metal substrate is observed on the surface of the metal substrate. Wherein the maximum value L of the major axis is not more than 5/6 times (L≤5 / 6T) the thickness T of the corrosion-resistant conductive skin blue film. Metal material having.

 (2) The metal material having a corrosion-resistant conductive film according to claim 1, wherein the second phase compound of the metal substrate observed on the surface of the metal substrate is substantially absent.

 (3) The second phase compound observed up to a depth of 5 μm below the surface of the metal substrate has a maximum major axis L of 5/6 or less times the thickness of the corrosion-resistant conductive film (L The metal material having a corrosion-resistant conductive film according to claim 1 or 2, wherein ≤ 5/6 T).

 (4) The metal material having a corrosion-resistant conductive film according to any one of claims 1 to 3, wherein substantially no second phase compound is observed up to a depth of 5 μm below the surface of the metal substrate. .

(5) The metal material having a corrosion-resistant conductive film according to claim 1 or 3, wherein the number of the second phase compounds observed on the surface of the metal substrate is 20 / ram ² or less.

 (6) The metal material having a corrosion-resistant conductive film according to any one of claims 1 to 5, wherein the metal substrate is an aluminum material made of aluminum or an aluminum alloy.

(7) The chemical composition of the aluminum material is less than 7% by mass of magnesium (Mg), less than 3% by mass of zinc (Zn), less than 0.01% by mass of silicon (Si), and less than 0% by mass of iron (Fe). Less than 1% by mass and copper (Cu) ◦. And the balance is aluminum (A1) and unavoidable impurity elements. 7. A metal material having the corrosion-resistant conductive film according to 6.

 (8) The metal material having a corrosion-resistant conductive film according to any one of claims 1 to 7, wherein the corrosion-resistant conductive film is a noble metal element film, a nickel film, or a copper film.

 (9) The metal material having a corrosion-resistant conductive film according to claim 8, wherein the corrosion-resistant conductive film is a noble metal element film having a thickness of 0.01 μm or more and 5 μm or less.

 (10) The metal material having a corrosion-resistant conductive film according to claim 8 or 9, wherein the noble metal element film is formed by a noble metal plating treatment.

 (11) The metal material having a corrosion-resistant conductive film according to claim 10, wherein the noble metal plating treatment is a gold plating treatment, and the noble metal plating film is a gold plating film.

 (12) The metal material having a corrosion-resistant conductive film according to claim 10, wherein the noble metal plating treatment is a platinum plating treatment, and the noble metal plating film is a platinum plating film.

 (13) The metal material having a corrosion-resistant conductive film according to claim 10, wherein the noble metal plating treatment is a platinum rhodium plating treatment, and the noble metal plating film is a platinum rhodium plating film.

(14) The corrosion-resistant conductive film has a thickness of 0.01 to 5 μπι and a polarization current of 10 μAm / cra ² or less measured by an electrochemical polarization characteristic evaluation method. 13. A metal material having the corrosion-resistant conductive film according to 13.

(15) A separator base for forming a separator that is interposed between the unit cells when a plurality of unit cells are stacked to form a fuel cell and forms a separator between the unit cells. A metal material having a corrosion-resistant conductive film according to any one of claims 1 to 14, which is a material.

 (16) In producing a metal material having a corrosion-resistant conductive film according to any one of claims 1 to 15, zinc is immersed in the metal substrate after pickling.

35

Corrected form (Rule 91) A method for producing a metal material having a corrosion-resistant conductive film, characterized by repeating a zinc immersion treatment at least four times, and then forming a corrosion-resistant conductive film on the surface of the metal substrate.

 (17) The method for producing a metal material having a corrosion-resistant conductive film according to claim 16, wherein the metal substrate is subjected to an etching treatment before the zinc immersion treatment.

 (18) The metal substrate is an aluminum material made of aluminum or an aluminum alloy, and the film thickness of the corrosion-resistant conductive film formed by precious metal plating is from 0.01 to 5 μιη. The method for producing a metal material having a corrosion-resistant conductive film according to claim 16 or 17, which is a noble metal plating film.

 (19) The metal substrate according to claim 17 or 18, wherein the surface roughness of the metal substrate before the etching treatment is adjusted to a range of 0.02 to 0.3 μηι by a surface polishing treatment. A method for producing a metal material having a corrosion-resistant conductive film.

(20) A metal substrate formed of a metal material and a film formed on the surface of the metal substrate and having a thickness of 0.01 to 5 μπ !, which was measured by an electrochemical polarization property evaluation method. A metal material having a corrosion-resistant conductive film, comprising: a corrosion-resistant conductive film having a polarization current of 10 aA / cm ² or less.

 (21) The metal substrate is a fuel cell forming material used for forming a fuel cell, and the corrosion-resistant conductive film is a noble metal plating film formed by a noble metal plating process. Item 20. A metal material having a corrosion-resistant conductive film according to Item 20.

(22) The fuel cell forming material is interposed between the electrodes of each unit cell adjacent to each other when forming a fuel cell by stacking a plurality of unit cells to form a separator that separates these unit cells. 22. The metal material having a corrosion-resistant conductive film according to claim 21, wherein a noble metal plating film is formed on at least the electrode contact surface of the separator substrate.

(23) The metal material having a corrosion-resistant conductive film according to claim 22, wherein the separator substrate has a reaction gas flow path formed on an electrode contact surface thereof.

(24) The fuel cell forming material is an electrode substrate of a unit cell constituting the fuel cell, and the electrode substrate has a noble metal plating film formed on a surface of the unit cell on the electrolyte side. A metal material having a corrosion-resistant conductive film according to (1).

 (25) The metal material having a corrosion-resistant conductive film according to claim 24, wherein the electrode substrate has a reaction gas flow path formed on a contact surface with an electrolyte forming a unit battery.

 (26) The metal material having a corrosion-resistant conductive film according to any one of claims 21 to 25, wherein the fuel cell forming material is formed of an aluminum material made of aluminum or an aluminum alloy.

 (27) The metal material having a corrosion-resistant conductive film according to any one of claims 21 to 26, wherein the noble metal plating film is formed on the entire surface of the fuel cell forming material.

 (28) The metal material having a corrosion-resistant conductive film according to any one of claims 21 to 27, wherein the noble metal plating process is a gold plating process, and the noble metal plating film is a gold plating film. .

 (29) The metal material having a corrosion-resistant conductive film according to any one of claims 21 to 27, wherein the noble metal plating treatment is a platinum plating treatment, and the noble metal plating film is a platinum plating film.

 (30) The metal material having a corrosion-resistant conductive film according to any one of claims 21 to 27, wherein the noble metal plating treatment is a platinum rhodium plating treatment, and the noble metal plating film is a platinum rhodium plating film.

 (31) A metal substrate is formed from a metal material, and after the metal substrate is subjected to an etching treatment, a zinc substitution treatment in which zinc is immersed after pickling is repeated four times or more. 0.0 1 to 5 ra corrosion resistance

37 Corrected Form (Rule 91) A method for producing a metal material having a corrosion-resistant conductive film, characterized by forming an electroconductive film.

 (32) The metal substrate is a fuel cell forming material used when forming a fuel cell, and the corrosion-resistant conductive film is a noble metal plating film formed by a noble metal plating process. 2. The method for producing a metal material having a corrosion-resistant conductive film according to 1.

 (33) The fuel cell forming material is interposed between the electrodes of each unit cell adjacent to each other when forming a fuel cell by stacking a plurality of unit cells to form a separator that separates these unit cells. 33. The method for producing a metal material having a corrosion-resistant conductive film according to claim 32, wherein a noble metal plating film is formed on at least the electrode contact surface of the separator substrate.

 (34) The method for producing a metal material having a corrosion-resistant conductive film according to claim 33, wherein the separator substrate has a reaction gas flow path formed on an electrode contact surface thereof.

 (35) The fuel cell-forming material is an electrode substrate of a unit cell constituting the fuel cell, and a metal plating film is formed on the electrode substrate on the electrolyte side surface of the unit cell. 3. The method for producing a metal material having a corrosion-resistant conductive film according to claim 1.

 (36) The method for producing a metal material having a corrosion-resistant conductive film according to claim 35, wherein the electrode substrate has a reaction gas flow path formed on a contact surface with an electrolyte forming a unit battery.

 (37) Pickling of zinc substitution treatment is 5-50 wt ° /. The method for producing a metal material having a corrosion-resistant conductive film according to any one of claims 31 to 36, wherein the method is performed by immersing in a pickling bath made of a concentrated nitric acid aqueous solution at room temperature for 5 to 120 seconds.

(38) Zinc immersion in the zinc substitution treatment was performed using an aqueous zinc oxide solution with a zinc oxide concentration of 1.5 to 60 g / L and an alkaline concentration of 40 to 400 g / L. The method for producing a metal material having a corrosion-resistant conductive film according to any one of claims 31 to 37, wherein the metal material is immersed in a zinc immersion bath at room temperature for 5 to 120 seconds.

 (39) The method for producing a metal material having a corrosion-resistant conductive film according to any one of claims 32 to 38, wherein the fuel cell forming material is formed of an aluminum material made of aluminum or an aluminum alloy. .

 (40) The method for producing a metal material having a corrosion-resistant conductive film according to any one of claims 32 to 39, wherein the noble metal plating film is formed on the entire surface of the fuel cell forming material.

 (41) The precious metal plating treatment is a gold plating treatment, and the precious metal plating skin film is a gold plating film. The metal material having a corrosion-resistant conductive film according to any one of claims 32 to 40, Production method.

 (42) The production of a metal material having a corrosion-resistant conductive film according to any of claims 32 to 40, wherein the noble metal plating treatment is a platinum plating treatment, and the noble metal plating film is a platinum plating film. Method.

 (43) The noble metal plating treatment is a platinum rhodium plating treatment, and the noble metal plating film is a platinum rhodium plating film. Production method.

 (44) The fuel cell forming material before the etching treatment has a surface roughness adjusted to a range of 0.02 to 0.3 μπι by surface polishing treatment. A method for producing a metal material having a corrosion-resistant conductive film according to any one of the above.

 (45) The surface polishing treatment according to claim 44, wherein the surface polishing treatment is any one treatment selected from electrolytic polishing treatment, mechanical polishing treatment, puff polishing treatment, and blast polishing treatment, or a combination of two or more treatments. A method for producing a metal material having the corrosion-resistant conductive film according to the above.

39 Corrected Ecchi (Rule 91)