JP2012164604A - Method for manufacturing metallic separator material for fuel cell, and metallic separator material for fuel cell - Google Patents
Method for manufacturing metallic separator material for fuel cell, and metallic separator material for fuel cell Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
Description
本発明は、ステンレス鋼薄板の表面にＡｕ被覆層を電解めっきして形成する燃料電池用金属セパレータ材料の製造方法、及び燃料電池用金属セパレータ材料に関する。 The present invention relates to a method for producing a metal separator material for a fuel cell, which is formed by electroplating an Au coating layer on the surface of a stainless steel sheet, and a metal separator material for a fuel cell.
固体高分子型の燃料電池用セパレータは電気伝導性を有し、燃料電池の各単セルを電気的に接続し、各単セルで発生したエネルギー（電気）を集電すると共に、各単セルへ供給する燃料ガス（燃料液体）や空気（酸素）の流路が形成されている。このセパレータは、インターコネクタ、バイポーラプレート、集電体とも称される。
このような燃料電池用セパレータとして、従来はカーボン板にガス流通路を形成したものが使用されていたが、材料コストや加工コストが大きいという問題がある。一方、カーボン板の代わりに金属板を用いる場合、高温で酸化性の雰囲気に曝されるために腐食や溶出が問題となる。このようなことから、ステンレス鋼板の表面にＡｕめっきを０．０１〜０．０６μｍ被覆する技術や（特許文献１）、ステンレス鋼板の表面にＡｕ，Ｒｕ、Ｒｈ、Ｐｄ、Ｏｓ、Ｉｒ及びＰｔ等から選ばれる貴金属をスパッタ成膜して導電部分を形成する技術（特許文献２）が知られている。
又、ステンレス鋼板の表面に、下地処理を施さずに酸性浴にてダイレクトに金めっきを施す技術（特許文献３）や、ステンレス鋼板の表面に酸化被膜を形成後に金めっきを施す技術（特許文献４）が報告されている。
一方、めっき浴に超音波振動を付与することで、高電流密度による高速めっきを行う技術（特許文献５）が報告されている。
Solid polymer fuel cell separators have electrical conductivity, and each unit cell of the fuel cell is electrically connected to collect energy (electricity) generated in each unit cell and to each unit cell. A flow path for supplying fuel gas (fuel liquid) and air (oxygen) is formed. This separator is also called an interconnector, a bipolar plate, or a current collector.
Conventionally, a fuel cell separator having a gas flow path formed on a carbon plate has been used, but there is a problem that the material cost and processing cost are high. On the other hand, when a metal plate is used instead of the carbon plate, corrosion and elution become a problem because it is exposed to an oxidizing atmosphere at a high temperature. For this reason, the technology of coating the surface of the stainless steel plate with Au plating of 0.01 to 0.06 μm (Patent Document 1), the surface of the stainless steel plate with Au, Ru, Rh, Pd, Os, Ir, Pt, etc. A technique (Patent Document 2) for forming a conductive portion by sputtering a noble metal selected from the above is known.
In addition, a technique for performing gold plating directly in an acidic bath without applying a base treatment to the surface of a stainless steel sheet (Patent Document 3), or a technique for performing gold plating after forming an oxide film on the surface of a stainless steel sheet (Patent Document) 4) has been reported.
On the other hand, a technique (Patent Document 5) that performs high-speed plating with high current density by applying ultrasonic vibration to a plating bath has been reported.
しかしながら、金は高価であることから、金の使用量（金膜の厚さ）を低減していく必要があり、ステンレス鋼薄板に直接薄い（ストライク，20nm以下）金めっきを行う必要がある。ところが、金めっきの厚みが２０ｎｍ未満に薄くなると、被膜欠陥が生じ易くなり、燃料電池用セパレータの耐食性を十分に確保できないという問題がある。特に、燃料電池用セパレータは酸性雰囲気に置かれるため、耐食性の点で厳しい環境下にある。
すなわち、本発明は、ステンレス鋼薄板表面に形成するＡｕ被覆層の厚みが薄くても耐食性に優れた燃料電池用金属セパレータ材料の製造方法及び燃料電池用金属セパレータ材料の提供を目的とする。
However, since gold is expensive, it is necessary to reduce the amount of gold used (gold film thickness), and it is necessary to perform thin (strike, 20 nm or less) gold plating directly on a stainless steel sheet. However, when the thickness of the gold plating is reduced to less than 20 nm, coating defects are likely to occur, and there is a problem that sufficient corrosion resistance of the fuel cell separator cannot be ensured. In particular, since the fuel cell separator is placed in an acidic atmosphere, it is in a severe environment in terms of corrosion resistance.
That is, an object of the present invention is to provide a method for producing a metal separator material for a fuel cell and a metal separator material for a fuel cell that are excellent in corrosion resistance even when the Au coating layer formed on the surface of the stainless steel thin plate is thin.
本発明の燃料電池用セパレータ材料の製造方法は、オーステナイト系ステンレス鋼薄板からなる基材の表面に、ｐＨ１．０以下のＡｕめっき浴を用いて厚み２０ｎｍ以下のＡｕ被覆層を形成する燃料電池用金属セパレータ材料の製造方法であって、前記基材及び／又は前記Ａｕめっき浴に超音波振動を付与した状態で電解めっきする。 The method for producing a separator material for a fuel cell according to the present invention is for a fuel cell in which an Au coating layer having a thickness of 20 nm or less is formed on the surface of a substrate made of austenitic stainless steel sheet using an Au plating bath having a pH of 1.0 or less. In the method for producing a metal separator material, electrolytic plating is performed in a state where ultrasonic vibration is applied to the substrate and / or the Au plating bath.
前記超音波振動の発振周波数を２５〜６０ｋＨｚとすることが好ましい。
前記Ａｕ被覆層をさらに封孔処理することが好ましい。
メルカプト系水溶液中で前記Ａｕ被覆層を電解処理して前記封孔処理を行うことが好ましい。
前記基材の表面粗さがRa≦0.08μmであることが好ましい。
The oscillation frequency of the ultrasonic vibration is preferably set to 25 to 60 kHz.
It is preferable that the Au coating layer is further sealed.
It is preferable to perform the sealing treatment by electrolytically treating the Au coating layer in a mercapto-based aqueous solution.
The surface roughness of the substrate is preferably Ra ≦ 0.08 μm.
本発明の燃料電池用セパレータ材料は、前記燃料電池用金属セパレータ材料の製造方法により製造されたものである。
前記基材の結晶粒内において、前記Ａｕ被覆層を原子間力顕微鏡により測定したときの算術表面粗さ（Ra）が３．０ｎｍ以下であることが好ましい。
The separator material for a fuel cell of the present invention is produced by the method for producing a metal separator material for a fuel cell.
In the crystal grains of the base material, the arithmetic surface roughness (Ra) when the Au coating layer is measured with an atomic force microscope is preferably 3.0 nm or less.
本発明によれば、ステンレス鋼薄板表面に形成するＡｕ被覆層の厚みが薄くても耐食性を向上させることができる。 According to the present invention, the corrosion resistance can be improved even if the Au coating layer formed on the stainless steel sheet surface is thin.
以下、本発明の実施形態に係る燃料電池用金属セパレータ材料の製造方法について説明する。なお、本発明において％とは、特に断らない限り、質量％を示すものとする。
又、本発明において「燃料電池用金属セパレータ」とは、電気伝導性を有し、各単セルを電気的に接続し、各単セルで発生したエネルギー（電気）を集電すると共に、各単セルへ供給する燃料ガス（燃料液体）や空気（酸素）の流路が形成されたものをいう。セパレータは、インターコネクタ、バイポーラプレート、集電体とも称される。
従って、詳しくは後述するが、燃料電池用セパレータとして、板状の基材表面に凹凸状の流路を設けたセパレータの他、上記したパッシブ型ＤＭＦＣ用セパレータのように板状の基材表面にガスやメタノールの流路孔が開口したセパレータを含む。
Hereinafter, the manufacturing method of the metal separator material for fuel cells which concerns on embodiment of this invention is demonstrated. In the present invention, “%” means “% by mass” unless otherwise specified.
Further, in the present invention, the “metal separator for fuel cell” has electrical conductivity, electrically connects each single cell, collects energy (electricity) generated in each single cell, and collects each single cell. A fuel gas (fuel liquid) or air (oxygen) flow path to be supplied to the cell is formed. The separator is also referred to as an interconnector, a bipolar plate, or a current collector.
Therefore, as will be described in detail later, as a separator for a fuel cell, in addition to a separator having an uneven flow path on a plate-like substrate surface, a plate-like substrate surface such as the above-described passive DMFC separator is used. It includes a separator with gas and methanol passage holes.
＜基材＞
燃料電池用金属セパレータ材料は耐食性と導電性が要求され、その基材には耐食性が求められる。このため基材には耐食性が良好で比較的低コストなオーステナイト系ステンレス鋼薄板を用いる。
オーステナイト系ステンレス鋼薄板の種類は特に制限されないが、例えば、ＪＩＳに規格するＳＵＳ２０１、ＳＵＳ３０４、ＳＵＳ３０４Ｌ、ＳＵＳ３０４ＬＮ、ＳＵＳ３１６、ＳＵＳ３１６Ｌ、ＳＵＳＸＭ７を挙げることができる。ここで、耐食性に優れる点で、ＳＵＳ３１６Ｌ（Ｍｏを２．５％程度添加したステンレス鋼）が好ましい。
基材の形状も特に制限されず、Ａｕをめっきできる形状であればよいが、セパレータ形状にプレス成形することから、薄板の厚みが０．０５〜０．３ｍｍであることが好ましい。
<Base material>
Metal separator materials for fuel cells are required to have corrosion resistance and conductivity, and the base material is required to have corrosion resistance. For this reason, an austenitic stainless steel sheet having good corrosion resistance and relatively low cost is used as the base material.
The type of the austenitic stainless steel sheet is not particularly limited, and examples thereof include SUS201, SUS304, SUS304L, SUS304LN, SUS316, SUS316L, and SUSXM7, which are compliant with JIS. Here, SUS316L (stainless steel to which Mo is added by about 2.5%) is preferable in terms of excellent corrosion resistance.
The shape of the substrate is not particularly limited as long as it is a shape that can be plated with Au. However, the thickness of the thin plate is preferably 0.05 to 0.3 mm because it is press-formed into a separator shape.
又、Ａｕ被覆層を平滑に成膜する観点から、基材表面も平滑化した方がよい。ステンレス鋼薄板の表面仕上げ法としては、従来からＢＡ（光輝焼鈍）、研磨仕上げ等が知られているが、２０ｎｍ以下の薄いＡｕ被覆層を形成する本発明においては、ＢＡ処理したステンレス鋼薄板が好ましい。
さらに、基材の表面粗さがRa≦0.08μmであると、Ａｕ被覆層を平滑に成膜する観点から好ましい。電解めっきは基材表面の凹凸の凸部に付きやすいため、基材の表面粗さRaを0.08μm以下とすることで均一にめっきが付き、ピンホールなどの欠陥が少なくすることができる。
Also, from the viewpoint of forming the Au coating layer smoothly, it is better to smooth the surface of the substrate. As surface finishing methods for stainless steel thin plates, BA (bright annealing), polishing finishing, and the like have been conventionally known. In the present invention for forming a thin Au coating layer of 20 nm or less, a BA-treated stainless steel thin plate is used. preferable.
Furthermore, when the surface roughness of the substrate is Ra ≦ 0.08 μm, it is preferable from the viewpoint of forming the Au coating layer smoothly. Since electrolytic plating tends to attach to the uneven surface of the base material surface, the surface roughness Ra of the base material is set to 0.08 μm or less so that plating is uniformly applied and defects such as pinholes can be reduced.
＜めっき＞
基材表面にＡｕ被覆層を電解めっきするため、ｐＨ１．０以下のＡｕめっき浴を用いる。ステンレス鋼薄板に直接Ａｕをめっきするためには、めっき浴のｐＨが１以下である必要があり、ｐＨ１．０以下のＡｕめっき浴を用いると、基材であるステンレス鋼表面のＣｒ酸化皮膜が除去されやすく、Ａｕ被覆層の密着性が向上する。
また、酸性Ａｕめっき浴を用い、基材表面に直接（ダイレクトに）Ａｕめっきすることで、めっき密着性が向上する。これは、従来からコネクタ材では基材にＮｉ下地めっきを行った後、Ａｕめっきを施しているが、Ｎｉの耐酸性が弱いため、燃料電池内の雰囲気によりＮｉめっきが剥がれてしまうからである。さらに、ｐＨ１．０以下の酸性Ａｕめっき浴は高電流密度でめっきが可能であるため、めっきの際に基材表面に水素が発生してステンレス表面が活性化され、Ａｕが付きやすくなる。
一方、Ａｕめっき浴のｐＨが１．０を超えると基材へのめっき密着性が低下する。なお、Ａｕめっき浴のｐＨが０．２未満になると、電解めっきの際に水素が過多に発生してめっき電流効率が低下するため、ｐＨは０．２以上が好ましい。
ｐＨ１．０以下のＡｕめっき浴としては硫酸水素ナトリウとシアン化金カリウムを主成分とする浴などが挙げられる。又、Ａｕ塩としては、シアン化金塩、等を用いることができ、Ａｕ塩の金濃度は２〜７ｇ／Ｌ程度とすることができる。
<Plating>
In order to electroplat the Au coating layer on the substrate surface, an Au plating bath having a pH of 1.0 or less is used. In order to directly plate Au on a stainless steel thin plate, the pH of the plating bath needs to be 1 or less. When an Au plating bath having a pH of 1.0 or less is used, the Cr oxide film on the surface of the stainless steel as a substrate is formed. It is easy to remove and the adhesion of the Au coating layer is improved.
In addition, plating adhesion is improved by directly (directly) Au plating on the surface of the substrate using an acidic Au plating bath. This is because, in the conventional connector materials, the Ni base plating is applied to the base material and then the Au plating is performed. However, since the acid resistance of Ni is weak, the Ni plating is peeled off by the atmosphere in the fuel cell. . Furthermore, since an acidic Au plating bath having a pH of 1.0 or less can be plated at a high current density, hydrogen is generated on the surface of the base material during the plating, the stainless steel surface is activated, and Au is easily attached.
On the other hand, when the pH of the Au plating bath exceeds 1.0, the plating adhesion to the substrate is lowered. If the pH of the Au plating bath is less than 0.2, excessive hydrogen is generated during electroplating and the plating current efficiency is lowered. Therefore, the pH is preferably 0.2 or more.
Examples of the Au plating bath having a pH of 1.0 or less include a bath mainly composed of sodium hydrogen sulfate and potassium gold cyanide. As the Au salt, a gold cyanide salt or the like can be used, and the gold concentration of the Au salt can be about 2 to 7 g / L.
Ａｕめっきの条件としては、電流密度が低いと基材の凸部に電流が集中してめっき層が平坦になり難く、又、めっき浴温が低いとめっき層が平坦になり難い傾向にある。
又、めっき液中の金濃度は１〜４ｇ／Ｌが好ましく、より好ましくは１〜２ｇ／Ｌである。金濃度が１ｇ／Ｌ未満であると、電流効率が低下してめっき層が平坦になり難い傾向にある。Ａｕめっきの電流密度は１〜８Ａ／ｄｍ２、好ましくは電流密度４〜８Ａ／ｄｍ２とするとよい。
As conditions for Au plating, when the current density is low, current concentrates on the convex portion of the substrate and the plating layer is difficult to flatten, and when the plating bath temperature is low, the plating layer tends to be difficult to flatten.
The gold concentration in the plating solution is preferably 1 to 4 g / L, more preferably 1 to 2 g / L. If the gold concentration is less than 1 g / L, the current efficiency tends to decrease and the plating layer tends not to be flat. The current density of Au plating is 1 to 8 A / dm 2 , preferably 4 to 8 A / dm 2 .
＜超音波振動の付与＞
また２０ｎｍを超えるＡｕめっき厚みでは問題とならないが、Ａｕめっきを厚み２０ｎｍ以下とすると、上記したＡｕめっき浴のｐＨや浴組成の調整だけでは十分でなく、めっき被膜のピンホールが増えて耐食性が低下する。このため、厚さ２０ｎｍ以下のＡｕめっきでは、超音波の照射が有効である。この理由は、Ａｕめっきの際に超音波を用いることで、Ａｕめっき浴が均一に攪拌され、浴中の金イオンが基材表面に均一に供給されるので，ピンホールを低減することができるからである。又、超音波によりＡｕめっき浴中にキャビテーションを起こさせ，基材表面に滞留する水素や不純物を浮き上がらせ，これらを起点としためっき欠陥（ピンホールなど）を低減することができる。
なお、超音波振動は、基材及び／又はＡｕめっき浴に付与すればよく、例えば超音波振動子をめっき浴中の基材に接触させたり、Ａｕめっき浴に超音波振動子を接触させることで、超音波振動を付与することができる。又、超音波振動の発振周波数によりＡｕめっき浴の攪拌状態、キャビテーションの状態が変わるが、周波数を２５〜６０ｋＨｚとすると、超音波の効果を安定して発揮することができる。
超音波振動子としては、例えばチタンやハステロイを外殻とした圧電セラミックなどを用いることができる。
<Applying ultrasonic vibration>
In addition, when the Au plating thickness exceeds 20 nm, there is no problem. However, if the Au plating thickness is 20 nm or less, it is not sufficient to adjust the pH and bath composition of the Au plating bath described above, and the pinholes of the plating film increase and corrosion resistance is increased. descend. For this reason, ultrasonic wave irradiation is effective in Au plating with a thickness of 20 nm or less. The reason for this is that by using ultrasonic waves during Au plating, the Au plating bath is uniformly stirred and the gold ions in the bath are uniformly supplied to the surface of the substrate, so that pinholes can be reduced. Because. Further, cavitation is caused in the Au plating bath by ultrasonic waves, hydrogen and impurities staying on the surface of the base material are lifted, and plating defects (pinholes and the like) starting from these can be reduced.
The ultrasonic vibration may be applied to the base material and / or the Au plating bath. For example, the ultrasonic vibrator is brought into contact with the base material in the plating bath, or the ultrasonic vibrator is brought into contact with the Au plating bath. Thus, ultrasonic vibration can be applied. Moreover, although the stirring state and cavitation state of the Au plating bath change depending on the oscillation frequency of the ultrasonic vibration, when the frequency is 25 to 60 kHz, the effect of the ultrasonic wave can be stably exhibited.
As the ultrasonic vibrator, for example, a piezoelectric ceramic having titanium or hastelloy as an outer shell can be used.
＜Ａｕ被覆層＞
基材表面（片面または両面）に形成するＡｕ被覆層の厚さは，コストの点から２０ｎｍ以下とするが、耐食性と電気特性（セパレータとMEAの接触抵抗）の観点から２ｎｍ以上とするとよい。好ましくはＡｕ被覆層の厚みを５〜２０ｎｍとし、より好ましくはＡｕ被覆層の厚みを５〜１０ｎｍにすると、耐食性が良好でかつコストを低減することができる。Ａｕ被覆層の厚みは、電解法や断面のＴＥＭ（透過型電子顕微鏡）像で算出することができる。
基材の結晶粒内において、原子間力顕微鏡により測定したＡｕ被覆層の算術表面粗さ（Ｒａ）が３．０ｎｍ以下であると好ましい。本発明者らの検討により、薄い（厚み２０ｎｍ以下の）Ａｕ被覆層においては、表面のＲａが大きくなるほど、基材からの金属溶出量も多くなることが判明した。この原因は明確ではないが、Ａｕ被覆層のＲａが大きいものは、電気めっき時に基材の特定の位置に集中して電析し、その分だけめっき層の厚みが薄い部分が生じ、被膜欠陥に至ることが考えられる。
なお、基材表面へのＡｕの電着状態は、基材の結晶粒内と結晶粒界とで異なる。具体的には、基材の粒界部分では電着が凹状となるので、基材の粒界を含む部分のＲａを原子間力顕微鏡（ＡＦＭ）で測定すると、Ｒａの測定値は大きくなる。そのため，本発明においては，基材の結晶粒内で測定したＲａをＡｕ被覆層のＲａとして採用する。
又、省金化の観点から、燃料電池用セパレータ材料を燃料電池用セパレータに加工した際に電極との接触面となる部分等、導電性が必要となる部分のみにＡｕめっきを施すことも可能である。
<Au coating layer>
The thickness of the Au coating layer formed on the substrate surface (one side or both sides) is 20 nm or less from the viewpoint of cost, but is preferably 2 nm or more from the viewpoint of corrosion resistance and electrical characteristics (contact resistance between separator and MEA). When the thickness of the Au coating layer is preferably 5 to 20 nm, and more preferably 5 to 10 nm, the corrosion resistance is good and the cost can be reduced. The thickness of the Au coating layer can be calculated by an electrolytic method or a cross-sectional TEM (transmission electron microscope) image.
In the crystal grains of the substrate, the arithmetic surface roughness (Ra) of the Au coating layer measured with an atomic force microscope is preferably 3.0 nm or less. As a result of studies by the present inventors, it has been found that in a thin Au coating layer (thickness of 20 nm or less), the amount of metal elution from the substrate increases as the surface Ra increases. Although the cause of this is not clear, when the Au coating layer has a large Ra, electrodeposition is concentrated at a specific position on the substrate during electroplating, resulting in a portion with a thinner plating layer, resulting in film defects. It can be thought of that.
In addition, the electrodeposition state of Au on the substrate surface is different between the crystal grains of the substrate and the crystal grain boundaries. Specifically, since electrodeposition is concave at the grain boundary portion of the substrate, the measured value of Ra increases when the Ra of the portion including the grain boundary of the substrate is measured with an atomic force microscope (AFM). Therefore, in this invention, Ra measured in the crystal grain of a base material is employ | adopted as Ra of Au coating layer.
In addition, from the viewpoint of saving money, it is possible to apply Au plating only to the parts that require electrical conductivity, such as the parts that will be in contact with the electrodes when the fuel cell separator material is processed into a fuel cell separator. It is.
図１は、後述する発明例１−３の燃料電池用セパレータ材料の断面のＴＥＭ像を示す。又、図２は、同様にして発明例１−５の燃料電池用セパレータ材料の断面のＴＥＭ像を示す。 FIG. 1 shows a TEM image of a cross section of a fuel cell separator material of Invention Example 1-3 described later. FIG. 2 shows a TEM image of a cross section of the fuel cell separator material of Invention Example 1-5 in the same manner.
２０ｎｍ以下の薄く柔らかい、Ａｕ被覆層の平滑性を評価する際、接触式表面粗さ計で測定するとナノレベルの凹凸の評価は困難となり、ステンレス鋼等の基材の粗さを測定することとなってしまう。そのため、本発明において、薄いＡｕ層の平滑性の評価に非接触の原子間力顕微鏡（ＡＦＭ）を用いる。
ＡＦＭにより測定したＡｕ被覆層のＲａが３．０ｎｍ以下になると、大幅に金属溶出量が少なくなる。Ａｕ被覆層のＲａは小さいほど好ましいが、Ｒａが０．５ｎｍ未満のめっき層を形成するのは実用上難しい。
When evaluating the smoothness of a thin and soft Au coating layer of 20 nm or less, it is difficult to evaluate nano level unevenness when measured with a contact-type surface roughness meter, and measuring the roughness of a substrate such as stainless steel turn into. Therefore, in the present invention, a non-contact atomic force microscope (AFM) is used for evaluating the smoothness of a thin Au layer.
When the Ra of the Au coating layer measured by AFM is 3.0 nm or less, the metal elution amount is greatly reduced. Although the Ra of the Au coating layer is preferably as small as possible, it is practically difficult to form a plating layer with an Ra of less than 0.5 nm.
Ａｕ被覆層のＲａを３．０ｎｍ以下にする方法としては、Ａｕめっき浴に硫酸水素ナトリウムを伝導塩として添加することが挙げられる。この場合、Ａｕめっき浴の組成としては、Ａｕ塩、硫酸水素ナトリウム、及び必要に応じてその他の添加剤を含むものを用いることができる。又、硫酸水素ナトリウムの濃度は、５０〜１００ｇ／Ｌ程度とすることができる。 As a method for setting the Ra of the Au coating layer to 3.0 nm or less, sodium hydrogen sulfate is added as a conductive salt to the Au plating bath. In this case, as the composition of the Au plating bath, one containing Au salt, sodium hydrogen sulfate, and other additives as required can be used. Moreover, the density | concentration of sodium hydrogensulfate can be about 50-100 g / L.
なお、図６に示すバイポーラ型セパレータにおいて、表裏面でＡｕ被覆層のめっき厚みを変えることが好ましい。燃料電池用金属セパレータは、一般的に上記した燃料電池用金属セパレータ材料の板材をプレス成形して得られた成形品をレーザー溶接などで２枚張り合わせることで製造され、張り合わせた内側（燃料電池用金属セパレータ材料の裏面側）には通常冷却水が流される。一方、セパレータの外側（燃料電池用金属セパレータ材料の表面側）は、膜電極接合体（ＭＥＡ；Membrane Electrode Assembly）と接して燃料ガス又は酸化剤ガスが流される。このように使用されることから、燃料電池用金属セパレータ材料の表面側は高耐食性を要求されるが、裏面側ではそれほど耐食性を必要としないので，表面側よりＡｕめっきの厚みを薄くしてもよい。又、使用部位や使用目的に応じて裏面側にはＡｕめっきをしなくてもよい。
又、Ａｕめっきは、セパレータ内の耐食性を要する部分（アクティブエリア）に対応する領域のみにめっきしてもよく、これにより金の使用量を減らすことができる（図６参照）。
In the bipolar separator shown in FIG. 6, it is preferable to change the plating thickness of the Au coating layer on the front and back surfaces. A fuel cell metal separator is generally manufactured by laminating two molded products obtained by press-molding a plate material of the above-described fuel cell metal separator material by laser welding or the like. Usually, cooling water is flowed to the back side of the metal separator material. On the other hand, the outer side of the separator (the surface side of the metal separator material for fuel cells) is in contact with a membrane electrode assembly (MEA) and a fuel gas or an oxidant gas is allowed to flow. Because it is used in this way, the surface side of the metal separator material for fuel cells is required to have high corrosion resistance, but the back side does not require so much corrosion resistance, so even if the Au plating thickness is made thinner than the surface side Good. Moreover, it is not necessary to carry out Au plating on the back surface side according to a use site | part and a use purpose.
In addition, Au plating may be performed only on a region corresponding to a portion (active area) that requires corrosion resistance in the separator, thereby reducing the amount of gold used (see FIG. 6).
＜封孔処理＞
Ａｕ被覆層が封孔処理されていることが好ましい。Ａｕ被覆層に被膜欠陥（ピンホール部）が存在しても、封孔処理によってこの欠陥を埋め、耐食性を維持することができる。Ａｕめっきの封孔処理は各種の方法が知られているが、メルカプト系水溶液中でＡｕ被覆層を電解処理するのが好ましい。メルカプト系水溶液は、メルカプト基含有化合物を水に溶解したものであり、メルカプト基含有化合物としては、例えば特開２００４−２６５６９５号公報に記載されたメルカプトベンゾチアゾール誘導体が挙げられる。メルカプト系化合物はピンホール部に吸着、結合し，耐食性を向上させる。
<Sealing treatment>
The Au coating layer is preferably sealed. Even if a coating defect (pinhole part) exists in the Au coating layer, the defect can be filled by the sealing treatment, and the corrosion resistance can be maintained. Various methods are known for sealing the Au plating, but it is preferable to electrolyze the Au coating layer in a mercapto-based aqueous solution. The mercapto aqueous solution is obtained by dissolving a mercapto group-containing compound in water. Examples of the mercapto group-containing compound include mercaptobenzothiazole derivatives described in JP-A No. 2004-265695. Mercapto compounds are adsorbed and bonded to the pinholes to improve corrosion resistance.
＜燃料電池用セパレータ＞
次に、本発明の燃料電池用セパレータ材料を用いた燃料電池用セパレータについて説明する。図６に示すように、燃料電池用セパレータは、上記した燃料電池用セパレータ材料を所定形状に加工してなり、燃料ガス（水素）又は燃料液体（メタノール）、空気（酸素）、冷却水等を流すための反応ガス流路又は反応液体流路（溝や開口）が形成されている。
<Separator for fuel cell>
Next, a fuel cell separator using the fuel cell separator material of the present invention will be described. As shown in FIG. 6, the fuel cell separator is formed by processing the above-described fuel cell separator material into a predetermined shape, such as fuel gas (hydrogen) or fuel liquid (methanol), air (oxygen), cooling water, etc. A reaction gas channel or a reaction liquid channel (groove or opening) for flow is formed.
＜積層型（アクティブ型）燃料電池用セパレータ＞
図３は、積層型（アクティブ型）燃料電池の単セルの断面図を示す。なお、図３では後述するセパレータ１０の外側にそれぞれ集電板１４０Ａ，１４０Ｂが配置されているが、通常、この単セルを積層してスタックを構成した場合、スタックの両端にのみ一対の集電板が配置される。
そして、セパレータ１０は電気伝導性を有し、後述するＭＥＡに接して集電作用を有し、各単セルを電気的に接続する機能を有する。又、後述するように、セパレータ１０には燃料ガスや空気（酸素）の流路となる溝が形成されている。
<Laminated (active) fuel cell separator>
FIG. 3 is a cross-sectional view of a single cell of a stacked (active) fuel cell. In FIG. 3, current collector plates 140A and 140B are respectively arranged outside the separator 10 described later. Usually, when a stack is formed by stacking single cells, a pair of current collectors is provided only at both ends of the stack. A board is placed.
The separator 10 has electrical conductivity, has a current collecting action in contact with an MEA described later, and has a function of electrically connecting each single cell. Further, as will be described later, the separator 10 is formed with a groove serving as a flow path for fuel gas and air (oxygen).
図３において、固体高分子電解質膜２０の両側にそれぞれアノード電極４０とカソード電極６０とが積層されて膜電極接合体（ＭＥＡ；Membrane Electrode Assembly）８０が構成されている。又、アノード電極４０とカソード電極６０の表面には、それぞれアノード側ガス拡散膜９０Ａ、カソード側ガス拡散膜９０Ｂがそれぞれ積層されている。本発明において膜電極接合体という場合、ガス拡散膜９０Ａ、９０Ｂを含んだ積層体としてもよい。又、例えばアノード電極４０やカソード電極６０の表面にガス拡散層が形成されている等の場合は、固体高分子電解質膜２０、アノード電極４０、カソード電極６０の積層体を膜電極接合体と称してもよい。 In FIG. 3, a membrane electrode assembly (MEA) 80 is configured by laminating an anode electrode 40 and a cathode electrode 60 on both sides of the solid polymer electrolyte membrane 20. An anode side gas diffusion film 90A and a cathode side gas diffusion film 90B are laminated on the surfaces of the anode electrode 40 and the cathode electrode 60, respectively. In the present invention, the membrane electrode assembly may be a laminate including the gas diffusion films 90A and 90B. For example, when a gas diffusion layer is formed on the surface of the anode electrode 40 or the cathode electrode 60, the laminated body of the solid polymer electrolyte membrane 20, the anode electrode 40, and the cathode electrode 60 is referred to as a membrane electrode assembly. May be.
ＭＥＡ８０の両側には、ガス拡散膜９０Ａ、９０Ｂにそれぞれ対向するようにセパレータ１０が配置され、セパレータ１０がＭＥＡ８０を挟持している。ＭＥＡ８０側のセパレータ１０表面には流路１０Ｌが形成され、後述するガスケット１２、流路１０Ｌ、及びガス拡散膜９０Ａ（又は９０Ｂ）で囲まれた内部空間２０内をガスが出入可能になっている。
そして、アノード電極４０側の内部空間２０には燃料ガス（水素等）が流れ、カソード電極６０側の内部空間２０に酸化性ガス（酸素、空気等）が流れることにより、電気化学反応が生じるようになっている。
On both sides of the MEA 80, the separator 10 is disposed so as to face the gas diffusion films 90A and 90B, respectively, and the separator 10 holds the MEA 80 therebetween. A flow path 10L is formed on the surface of the separator 10 on the MEA 80 side, and gas can enter and leave the interior space 20 surrounded by a gasket 12, a flow path 10L, and a gas diffusion film 90A (or 90B) described later. .
A fuel gas (hydrogen or the like) flows in the internal space 20 on the anode electrode 40 side, and an oxidizing gas (oxygen, air or the like) flows in the internal space 20 on the cathode electrode 60 side, so that an electrochemical reaction occurs. It has become.
アノード電極４０とガス拡散膜９０Ａの周縁の外側は、これらの積層厚みとほぼ同じ厚みの枠状のシール部材３１で囲まれている。又、シール部材３１とセパレータ１０の周縁との間には、セパレータに接して略枠状のガスケット１２が介装され、ガスケット１２が流路１０Ｌを囲むようになっている。さらに、セパレータ１０の外面（ＭＥＡ８０側と反対側の面）にはセパレータ１０に接して集電板１４０Ａ（又は１４０Ｂ）が積層され、集電板１４０Ａ（又は１４０Ｂ）とセパレータ１０の周縁との間に略枠状のシール部材３２が介装されている。
シール部材３１及びガスケット１２は、燃料ガス又は酸化ガスがセル外に漏れるのを防止するシールを形成する。又、単セルを複数積層してスタックにした場合、セパレータ１０の外面と集電板１４０Ａ（又は１４０Ｂ）との間の空間２１には空間２０と異なるガス（空間２０に酸化性ガスが流れる場合、空間２１には水素が流れる）が流れる。従って、シール部材３２もセル外にガスが漏れるのを防止する部材として使われる。
The outer periphery of the periphery of the anode electrode 40 and the gas diffusion film 90 </ b> A is surrounded by a frame-shaped seal member 31 having substantially the same thickness as the laminated thickness. A substantially frame-shaped gasket 12 is interposed between the seal member 31 and the peripheral edge of the separator 10 so as to contact the separator, and the gasket 12 surrounds the flow path 10L. Furthermore, a current collector plate 140A (or 140B) is laminated on the outer surface of the separator 10 (the surface opposite to the MEA 80 side) in contact with the separator 10, and between the current collector plate 140A (or 140B) and the periphery of the separator 10 is stacked. A substantially frame-shaped sealing member 32 is interposed between the two.
The seal member 31 and the gasket 12 form a seal that prevents fuel gas or oxidizing gas from leaking out of the cell. When a plurality of single cells are stacked to form a stack, a gas different from the space 20 (when an oxidizing gas flows into the space 20) is formed in the space 21 between the outer surface of the separator 10 and the current collector plate 140A (or 140B). , Hydrogen flows in the space 21). Therefore, the seal member 32 is also used as a member for preventing gas from leaking outside the cell.
そして、ＭＥＡ８０（及びガス拡散膜９０Ａ、９０Ｂ）、セパレータ１０、ガスケット１２、集電板１４０Ａ、１４０Ｂを含んで燃料電池セルが構成され、複数の燃料電池セルを積層して燃料電池スタックが構成される。 The fuel cell is configured to include the MEA 80 (and the gas diffusion films 90A and 90B), the separator 10, the gasket 12, and the current collector plates 140A and 140B, and a fuel cell stack is configured by stacking a plurality of fuel cells. The
図３に示す積層型（アクティブ型）燃料電池は、上記した水素を燃料として用いる燃料電池のほか、メタノールを燃料として用いるＤＭＦＣにも適用することができる。 The stacked (active) fuel cell shown in FIG. 3 can be applied not only to the above-described fuel cell using hydrogen as a fuel, but also to a DMFC using methanol as a fuel.
＜平面型（パッシブ型）燃料電池用セパレータ＞
図４は、平面型（パッシブ型）燃料電池の単セルの断面図を示す。なお、図４ではセパレータ１００の外側にそれぞれ集電板１４０が配置されているが、通常、この単セルを積層してスタックを構成した場合、スタックの両端にのみ一対の集電板が配置される。
なお，図４において、ＭＥＡ８０の構成は図３の燃料電池と同一であるので同一符号を付して説明を省略する（図４では、ガス拡散膜９０Ａ、９０Ｂの記載を省略しているが、ガス拡散膜９０Ａ、９０Ｂを有していてもよい）。
<Flat type (passive type) fuel cell separator>
FIG. 4 shows a cross-sectional view of a single cell of a planar (passive type) fuel cell. In FIG. 4, current collector plates 140 are arranged outside the separator 100. Normally, when a stack is formed by stacking single cells, a pair of current collector plates is arranged only at both ends of the stack. The
In FIG. 4, the configuration of the MEA 80 is the same as that of the fuel cell of FIG. Gas diffusion films 90A and 90B may be included).
図４において、セパレータ１００は電気伝導性を有し、ＭＥＡに接して集電作用を有し、各単セルを電気的に接続する機能を有する。又、後述するように、セパレータ１００には燃料液体や空気（酸素）の流路となる孔が形成されている。
セパレータ１００は、断面がクランク形状になるよう、長尺平板状の基材の中央付近に段部１００ｓを形成してなり、段部１００ｓを介して上方に位置する上側片１００ｂと、段部１００ｓを介して下方に位置する下側片１００ａとを有する。段部１００ｓはセパレータ１００の長手方向に垂直な方向に延びている。
そして、複数のセパレータ１００を長手方向に並べ、隣接するセパレータ１００の下側片１００ａと上側片１００ｂとの間に空間を形成させ、この空間にＭＥＡ８０を介装する。２つのセパレータ１００でＭＥＡ８０が挟まれた構造体が単セル３００となる。このようにして、複数のＭＥＡ８０がセパレータ１００を介して直列に接続されたスタックが構成される。
In FIG. 4, the separator 100 has electrical conductivity, has a current collecting action in contact with the MEA, and has a function of electrically connecting each single cell. In addition, as will be described later, the separator 100 is formed with holes serving as fuel liquid and air (oxygen) flow paths.
The separator 100 is formed with a step portion 100s in the vicinity of the center of the long flat plate-like base material so that the cross section has a crank shape, an upper piece 100b positioned above the step portion 100s, and a step portion 100s. And a lower piece 100a located below. The step portion 100 s extends in a direction perpendicular to the longitudinal direction of the separator 100.
A plurality of separators 100 are arranged in the longitudinal direction, and a space is formed between the lower piece 100a and the upper piece 100b of the adjacent separators 100, and the MEA 80 is interposed in this space. A structure in which the MEA 80 is sandwiched between the two separators 100 is a single cell 300. In this way, a stack in which a plurality of MEAs 80 are connected in series via the separator 100 is configured.
図４に示す平面型（パッシブ型）燃料電池は、上記したメタノールを燃料として用いるＤＭＦＣのほか、水素を燃料として用いる燃料電池にも適用することができる。又、平面型（パッシブ型）燃料電池用セパレータの開口部の形状や個数は限定されず、開口部として上記した孔の他、スリットとしてもよく、セパレータ全体が網状であってもよい。 The planar (passive) fuel cell shown in FIG. 4 can be applied to a fuel cell using hydrogen as a fuel in addition to the DMFC using methanol as a fuel. Further, the shape and number of openings of the planar (passive type) fuel cell separator are not limited, and the openings may be slits in addition to the holes described above, or the entire separator may be net-like.
＜燃料電池用スタック＞
本発明の燃料電池用スタックは、本発明の燃料電池用セパレータ材料を用いてなる。
燃料電池用スタックは、１対の電極で電解質を挟み込んだセルを複数個直列に接続したものであり、各セルの間に燃料電池用セパレータが介装されて燃料ガスや空気を遮断する。燃料ガス(H2)が接触する電極が燃料極(アノード)であり、空気(O2) が接触する電極が空気極(カソード)である。
燃料電池用スタックの構成例は、既に図３及び図４で説明した通りであるが、これに限定されない。
<Fuel cell stack>
The fuel cell stack of the present invention uses the fuel cell separator material of the present invention.
The fuel cell stack is formed by connecting a plurality of cells in which an electrolyte is sandwiched between a pair of electrodes, and a fuel cell separator is interposed between the cells to block fuel gas and air. The electrode in contact with the fuel gas (H 2 ) is the fuel electrode (anode), and the electrode in contact with the air (O 2 ) is the air electrode (cathode).
The configuration example of the fuel cell stack is as described with reference to FIGS. 3 and 4, but is not limited thereto.
＜試料の作製＞
表１に示す組成のオーステナイト系ステンレス鋼板（表１にＪＩＳ規格で記載）に対して冷間圧延と焼鈍を繰り返し、厚みが０．１０ｍｍの基材を得た。なお、表面粗さを小さくし、表面の清浄度を上げてめっき欠陥を抑制するため、仕上げ圧延はロール粗さＲａ≦０．０８μｍに制御した幅４５０ｍｍのロールを用い、表面酸化を抑制するため、焼鈍は全て水素90％以上の雰囲気内で行った。ロールの表面粗さは触針式粗さ計（ミツトヨ社製のＳＪ−４００）を用い、ＪＩＳ Ｂ ０６０１に準拠して測定した。
この基材に、前処理として市販の脱脂液を用いて電解脱脂後、水洗し、さらに電解酸洗後、水洗を施した。電解脱脂は、水酸化ナトリウム40g/Lと非イオン系界面活性剤5g/Lとを含有する脱脂液を使用し，基材を陰極にして10秒間電解した。電解酸洗は硫酸50g/Lを含有する水溶液を使用し，基材を陰極にして10秒間電解した。
<Preparation of sample>
Cold rolling and annealing were repeated on an austenitic stainless steel sheet having the composition shown in Table 1 (described in Table 1 in JIS standards) to obtain a base material having a thickness of 0.10 mm. In order to reduce the surface roughness, increase the surface cleanliness and suppress plating defects, the finish rolling uses a roll having a width of 450 mm controlled to a roll roughness Ra ≦ 0.08 μm, and suppresses surface oxidation. All annealing was performed in an atmosphere of 90% hydrogen or more. The surface roughness of the roll was measured according to JIS B 0601 using a stylus roughness meter (SJ-400 manufactured by Mitutoyo Corporation).
This substrate was subjected to electrolytic degreasing using a commercially available degreasing solution as a pretreatment, followed by washing with water, followed by electrolytic pickling and then washing with water. For electrolytic degreasing, a degreasing solution containing 40 g / L of sodium hydroxide and 5 g / L of a nonionic surfactant was used, and electrolysis was performed for 10 seconds using the substrate as a cathode. For the electrolytic pickling, an aqueous solution containing 50 g / L of sulfuric acid was used, and electrolysis was performed for 10 seconds using the base material as the cathode.
次に、前処理後の基材に直接Ａｕめっきを所定厚み（表１参照）行い、燃料電池用セパレータ材料を作製した。ここで、図５に示すように、Ａｕめっき槽６の底部にハステロイを外殻とした超音波振動子（（株）サンテック製）４を配置し、Ａｕめっき槽６内のＡｕめっき浴に超音波振動を与えつつ、アノード８に対向する基材２に電解めっきを行った。なお、Ａｕめっき槽６の側面にはシール構造６ａが設けられ、基材２（ステンレス条）はシール構造６ａを通ってＡｕめっき槽６の側面を通過しつつ、めっきされるようになっている。
Ａｕめっき液（シアン系）は、シアン化金カリウム（ＩＩＩ）（金濃度：１〜２ｇ／Ｌ）、硫酸水素ナトリウム５０〜１００ｇ／Ｌのものを用い、ｐＨを表１のように変化させた。ｐＨの調整は硫酸水素ナトリウムの添加量を変えて行った。なお、Ａｕめっきの際、めっき浴の金濃度１〜４ｇ／Ｌ、電流密度１〜８Ａ／ｄｍ２、の範囲に管理すれば特に問題はなかった。
Next, Au plating was directly performed on the base material after the pretreatment with a predetermined thickness (see Table 1) to produce a fuel cell separator material. Here, as shown in FIG. 5, an ultrasonic vibrator (made by Suntec Co., Ltd.) 4 having Hastelloy as the outer shell is disposed at the bottom of the Au plating tank 6, and the Au plating bath in the Au plating tank 6 is super Electrolytic plating was performed on the substrate 2 facing the anode 8 while applying sonic vibration. A seal structure 6a is provided on the side surface of the Au plating tank 6, and the base material 2 (stainless steel strip) is plated while passing through the side surface of the Au plating tank 6 through the seal structure 6a. .
The Au plating solution (cyanide) used was potassium gold cyanide (III) (gold concentration: 1 to 2 g / L) and sodium hydrogen sulfate 50 to 100 g / L, and the pH was changed as shown in Table 1. . The pH was adjusted by changing the amount of sodium hydrogen sulfate added. In the Au plating, there was no particular problem if the gold concentration in the plating bath was controlled within the range of 1 to 4 g / L and the current density of 1 to 8 A / dm 2 .
さらに、一部の燃料電池用セパレータ材料（表１の発明例3-1,3-2）については、Ａｕめっきを行った後に封孔処理を行った。封孔処理はメルカプトベンゾチアゾールのナトリウム塩を1g/L含有する水溶液（発明例３−１），ベンゾトリアゾールのナトリウム塩を1g/L含有する水溶液（発明例３−２）を使用し，燃料電池用セパレータ材料を陽極にして10秒間電解処理して行った。 Further, some fuel cell separator materials (Invention Examples 3-1 and 3-2 in Table 1) were subjected to sealing after Au plating. Sealing treatment uses an aqueous solution containing 1 g / L of the sodium salt of mercaptobenzothiazole (Invention Example 3-1) and an aqueous solution containing 1 g / L of the sodium salt of benzotriazole (Invention Example 3-2). Electrolytic treatment was carried out for 10 seconds using the separator material for the anode as an anode.
以上のようにして作製した燃料電池用セパレータ材料表面の算術平均粗さＲａ、及び各種特性を以下のように測定した。 The arithmetic average roughness Ra and various characteristics of the surface of the fuel cell separator material produced as described above were measured as follows.
＜表面粗さ＞
めっき前基材の表面粗さＲａはＪＩＳ Ｂ ０６０１に準拠し、非接触式三次元測定装置（三鷹光器社製、型式ＮＨ−３）を用い、カットオフ０．２５ｍｍ、測定長さ１．５０ｍｍ、ｎ＝５で測定し、その平均値をＲａ値とした、めっき後のＡｕ被覆層の表面粗さＲａは、原子間力顕微鏡（島津製作所社製のＳＰＭ−９６００）を用い、ダイナミックモード（非接触方式）で、走査範囲１μｍ×１μｍ、走査速度０．８Ｈｚで、Ａｕめっき前の基材の結晶粒内に相当する場所をｎ＝３で測定し、その平均値をＲａの値として用いた。
<Surface roughness>
The surface roughness Ra of the base material before plating is based on JIS B 0601, using a non-contact type three-dimensional measuring device (manufactured by Mitaka Kogyo Co., Ltd., model NH-3), with a cutoff of 0.25 mm and a measurement length of 1. The surface roughness Ra of the Au coating layer after plating, measured at 50 mm and n = 5, with the average value as the Ra value, was measured using an atomic force microscope (SPM-9600 manufactured by Shimadzu Corp.) (Non-contact method) With a scanning range of 1 μm × 1 μm, a scanning speed of 0.8 Hz, the location corresponding to the crystal grains of the base material before Au plating is measured at n = 3, and the average value is taken as the value of Ra Using.
＜Ａｕ被覆層の密着性＞
Ａｕめっき材を９０度の角度に折り曲げ、次に曲げ部を０度に戻し、曲げ部にセロテープ（登録商標）を貼り付けてすぐに剥がし、Ａｕ被覆層の剥離の有無を光学顕微鏡を用いて調査した。テープにＡｕ被覆層が付着していないものを密着性が良好（ＯＫ）とした。
<Adhesion of Au coating layer>
The Au plating material is bent at an angle of 90 degrees, then the bent part is returned to 0 degree, and the cellophane (registered trademark) is attached to the bent part and peeled off immediately, and the presence or absence of peeling of the Au coating layer is checked using an optical microscope. investigated. A tape having no Au coating layer attached to the tape was considered to have good adhesion (OK).
＜耐食性＞
燃料電池の発電性能（出力、耐久性など）は、セパレータからの溶出イオン量が少ないほど良好であり、発電環境を模擬した耐食性試験ではセパレータの腐食電流密度として1.0×10-5(A/cm2)未満が要求されている。そこで、各燃料電池用セパレータ材料の腐食電流密度を測定した。測定は燃料電池の発電環境を模擬するよう、試験片に０．８Ｖ（ＳＨＥ）の電位を印加させた状態で、９０℃，ｐＨ３の硫酸溶液に浸漬し、２０時間経過時に試験片に流れる電流を測定した。そして、以下の基準で耐食性を評価した。評価が◎〜△であれば実用上問題はない。
◎：腐食電流密度が1×10-7(A/cm2)未満
○：腐食電流密度が1×10-7(A/cm2)以上1×10-6(A/cm2)未満
△：腐食電流密度が1×10-6(A/cm2)以上1×10-5(A/cm2)未満
×：腐食電流密度が1×10-5(A/cm2)以上
<Corrosion resistance>
The power generation performance (output, durability, etc.) of the fuel cell is better as the amount of ions eluted from the separator is smaller. In the corrosion resistance test simulating the power generation environment, the corrosion current density of the separator is 1.0 × 10 -5 (A / cm Less than 2 ) is required. Accordingly, the corrosion current density of each fuel cell separator material was measured. The measurement is performed by immersing the test piece in a sulfuric acid solution at 90 ° C. and pH 3 with a potential of 0.8 V (SHE) applied to the test piece so as to simulate the power generation environment of the fuel cell, and the current flowing through the test piece after 20 hours. Was measured. And corrosion resistance was evaluated according to the following criteria. If the evaluation is A to B, there is no practical problem.
◎: Corrosion current density is less than 1 × 10 -7 (A / cm 2 ) ○: Corrosion current density is 1 × 10 -7 (A / cm 2 ) or more and less than 1 × 10 -6 (A / cm 2 ) △: Corrosion current density is 1 × 10 -6 (A / cm 2 ) or more and less than 1 × 10 -5 (A / cm 2 ) ×: Corrosion current density is 1 × 10 -5 (A / cm 2 ) or more
得られた結果を表１に示す。なお、表１のＡｕめっき厚の表面と裏面は、それぞれ燃料電池にセパレータとして組んだ時の電解質膜側（表面）、冷却水側（裏面）に対応したものであり、耐食性の評価は各燃料電池用セパレータ材料の表面でのみ行った。 The obtained results are shown in Table 1. The front and back surfaces of the Au plating thickness in Table 1 correspond to the electrolyte membrane side (front surface) and the cooling water side (back surface) when assembled as a separator in a fuel cell, respectively. Corrosion resistance is evaluated for each fuel. It was performed only on the surface of the battery separator material.
表１から明らかなように、ｐＨ１．０以下のＡｕめっき浴を用い、超音波振動を付与した状態で電解めっきした各実施例の場合、Ａｕ被覆層の厚みが２０ｎｍ以下であっても、Ａｕ被覆層の密着性に優れ、耐食性にも優れていた。
なお、Ａｕめっき厚及びめっき浴のｐＨを同一とした発明例２−１〜２−４において、超音波振動の発振周波数をそれぞれ２５、６０ｋＨｚとした発明例２−１、２−２は他の発明例よりも腐食電流密度が小さく、耐食性と発電性能がより優れていた。
又、Ａｕめっき後に封孔処理を施した発明例３−１、３−２の場合、Ａｕめっき厚、めっき浴のｐＨ及び超音波振動の発振周波数を同一とした発明例１−４、１−８に比べ、腐食電流密度が小さく、耐食性がより優れていた。
又、基材の表裏でＡｕめっき厚をそれぞれ変えた発明例４−１〜４−３の場合も、耐食性が優れていた。
As is clear from Table 1, in the case of each of the examples in which the electroplating was performed using an Au plating bath having a pH of 1.0 or less and ultrasonic vibration was applied, the Au coating layer had a thickness of 20 nm or less. Excellent adhesion of the coating layer and excellent corrosion resistance.
Inventive Examples 2-1 and 2-4 in which the Au plating thickness and the pH of the plating bath are the same, Inventive Examples 2-1 and 2-2 in which the oscillation frequency of ultrasonic vibration is 25 and 60 kHz, respectively, The corrosion current density was smaller than that of the inventive examples, and the corrosion resistance and power generation performance were more excellent.
In the case of Invention Examples 3-1 and 3-2 in which sealing treatment was performed after Au plating, Invention Examples 1-4 and 1 where the Au plating thickness, the pH of the plating bath, and the oscillation frequency of ultrasonic vibration were the same. Compared to 8, the corrosion current density was small and the corrosion resistance was more excellent.
Moreover, also in the case of invention examples 4-1 to 4-3 in which the Au plating thicknesses were changed on the front and back of the base material, the corrosion resistance was excellent.
なお、ロール粗さがＲａ＞０．０８μｍのロールで基材を仕上げ圧延し、基材の表面粗さＲａも０．０８μｍを超えた発明例５−１の場合、他の条件が同一の発明例１−３に比べ、腐食電流密度が大きくなったが実用上は問題ない。
又、Ａｕめっき浴中の金濃度をそれぞれ４.５ｇ／Ｌ、５．０ｇ／Ｌとした発明例６−１、６−２の場合、金濃度が１〜４ｇ／Ｌでありその他の条件が同一の発明例１−４に比べ、腐食電流密度が大きくなったが実用上は問題ない。ここで、発明例６−２の場合、Ａｕ被覆層のＲａが３．０ｎｍを超え、腐食電流密度が大きくなった。
In addition, in the case of Invention Example 5-1, in which the base material is finish-rolled with a roll having a roll roughness Ra> 0.08 μm, and the surface roughness Ra of the base material also exceeds 0.08 μm, the other conditions are the same. Compared with Example 1-3, although the corrosion current density became large, there is no problem in practical use.
In the case of Invention Examples 6-1 and 6-2 in which the gold concentration in the Au plating bath is 4.5 g / L and 5.0 g / L, respectively, the gold concentration is 1 to 4 g / L, and other conditions are Although the corrosion current density is larger than that of the same Invention Example 1-4, there is no problem in practical use. Here, in Invention Example 6-2, the Ra of the Au coating layer exceeded 3.0 nm, and the corrosion current density increased.
一方、Ａｕめっき浴のｐＨが１．０を超えた比較例１−１の場合、Ａｕ被覆層の密着性及び耐食性がいずれも劣った。
超音波振動を付与せずにＡｕめっきを行った比較例１−２の場合、耐食性が劣った。
又、超音波振動を付与せずにＡｕめっきを行った後、封孔処理を施した比較例３−１の場合も、耐食性が劣った。
On the other hand, in the case of Comparative Example 1-1 in which the pH of the Au plating bath exceeded 1.0, both the adhesion and corrosion resistance of the Au coating layer were inferior.
In the case of Comparative Example 1-2 in which Au plating was performed without applying ultrasonic vibration, the corrosion resistance was inferior.
Further, in Comparative Example 3-1, in which Au plating was performed without applying ultrasonic vibration and then sealing treatment was performed, the corrosion resistance was inferior.
２ 基材
４ 超音波振動子
６ Ａｕめっき槽
８ アノード
１０、１００ セパレータ
１２、１２Ｂ ガスケット
２０ 固体高分子電解質膜
４０ アノード電極
６０ カソード電極
８０ 膜電極接合体（ＭＥＡ）
2 Base Material 4 Ultrasonic Vibrator 6 Au Plating Tank 8 Anode 10, 100 Separator 12, 12B Gasket 20 Solid Polymer Electrolyte Membrane 40 Anode Electrode 60 Cathode Electrode 80 Membrane Electrode Assembly (MEA)
Claims (9)
前記基材及び／又は前記Ａｕめっき浴に超音波振動を付与した状態で電解めっきする燃料電池用金属セパレータ材料の製造方法。 A method for producing a metal separator material for a fuel cell, wherein an Au coating layer having a thickness of 20 nm or less is formed on a surface of a base material made of austenitic stainless steel thin plate using an Au plating bath having a pH of 1.0 or less,
A method for producing a metal separator material for a fuel cell, in which electrolytic plating is performed in a state where ultrasonic vibration is applied to the substrate and / or the Au plating bath.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5845395A (en) * | 1981-09-11 | 1983-03-16 | Konishiroku Photo Ind Co Ltd | Electroplating or electrolyzing method |
| JP2002256479A (en) * | 2001-03-05 | 2002-09-11 | Alps Electric Co Ltd | Method and equipment for plating |
| JP2004296381A (en) * | 2003-03-28 | 2004-10-21 | Honda Motor Co Ltd | Metal separator for fuel cell and its manufacturing method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS5845395A (en) * | 1981-09-11 | 1983-03-16 | Konishiroku Photo Ind Co Ltd | Electroplating or electrolyzing method |
| JP2002256479A (en) * | 2001-03-05 | 2002-09-11 | Alps Electric Co Ltd | Method and equipment for plating |
| JP2004296381A (en) * | 2003-03-28 | 2004-10-21 | Honda Motor Co Ltd | Metal separator for fuel cell and its manufacturing method |
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| JP2021051857A (en) * | 2019-09-24 | 2021-04-01 | トヨタ自動車株式会社 | Manufacturing method of fuel cell |
| JP7215384B2 (en) | 2019-09-24 | 2023-01-31 | トヨタ自動車株式会社 | Fuel cell manufacturing method |
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