JP2011029008A - Base material for metal separator, method of manufacturing the same, and metal separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base material for metal separator having low contact resistance by coating an ultrathin precious metal over the surface of a metal thin plate comprising a stainless steel, etc., and to provide a method of manufacturing the base material for metal separator, and the metal separator for fuel cell using the base material at low cost. <P>SOLUTION: The base material 1a for metal separator includes the metal thin plate 2 and an Au (precious metal) film 20. The metal thin plate 2 has a surface 3 coming into contact with an electrode of the fuel cell, and surface roughness Rz of the surface 3 is 1-10 μm, and average length RSm of contour curved line element of the surface 3 is 20-150 μm. The Au film coats the surface 3 of the metal thin plate 2 and has average film thickness of ≤10 nm. On the surface 3, a protrusion 3h coated by the precious metal film, whose maximum film thickness is ≥15 nm, occupies ≥20% of the protrusion 3h of the entire surface 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a metal separator substrate for use in a fuel cell, a method for producing the same, and a metal separator for a fuel cell using the substrate.

  A metal separator used in a polymer electrolyte fuel cell or the like (hereinafter simply referred to as a fuel cell) is required to have high conductivity (low contact resistance). The low contact resistance is an important factor for improving battery performance since recent fuel cells have a stack structure in which 10 to 500 unit cells are stacked. In order to satisfy the above characteristics, for example, a metal separator in which a surface of a thin plate made of stainless steel is coated with a noble metal such as Au is applied.

For example, a base material made of stainless steel of SUS304 is press-molded to form an inner concavo-convex portion, and the concavo-convex portion is coated with an Au base plating layer (first plating layer), and only the convex portion is made of Au. A fuel cell separator has been proposed in which a partial plating layer (second plating layer) is coated and the thickness of the two Au plating layers is 0.05 to 0.09 μm (50 to 90 nm) (for example, a patent) Reference 1).
However, if the Au plating layer having a thickness of 50 to 90 nm is coated on the surface of the base material like the fuel cell separator, the cost is increased. From the viewpoint of cost countermeasures, the thickness of the Au plating layer needs to be 10 nm or less. However, there has been a problem that the contact resistance becomes high when the level is thin.

JP 2001-345109 A (pages 1 to 6, FIGS. 1 to 4)

  The present invention solves the problems described in the background art, and covers a surface of a thin metal plate made of stainless steel or the like with an extremely thin noble metal film, and has a low contact resistance, and a method for producing the same And providing a metal separator for a fuel cell using the substrate at a low cost.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, the present invention is based on the inventors' diligent research. As a result, the unevenness on the surface of the metal thin plate as the base material is controlled within a predetermined range, and the protrusion is preferentially coated with a noble metal film. Thus, it is based on the knowledge that low contact resistance can be obtained even with a noble metal film having an average film thickness of 10 nm or less.
That is, the base material for metal separator of the present invention (Claim 1) has a surface in contact with the electrode of the fuel cell, the surface roughness Rz of the surface is 1 to 10 μm, and the contour curve element of the surface A metal thin plate having an average length RSm of 20 to 150 μm and a noble metal film having an average film thickness of 10 nm or less coated on the surface of the metal thin plate, and a noble metal film having a maximum film thickness of 15 nm or more on the surface. The covered convex portion occupies 20% or more of the convex portion of the entire surface.

The surface roughness Rz (maximum height) is set to 1 to 10 μm. If the surface roughness Rz is less than 1 μm, the difference in height between the convex portions and the concave portions on the surface is too small, and the thickness of the noble metal film is reduced between them. It is difficult to obtain an effective difference. On the other hand, if the surface roughness Rz exceeds 10 μm, the difference in height between the convex portions and the concave portions on the surface becomes excessive, which may impair the moldability as a separator base material when molding into a metal separator. Because there is.
In addition, the average length RSm of the contour curve element is set to 20 to 150 μm. If the average length RSm is less than 20 μm, the interval (pitch) between the plurality of irregularities in the lateral direction along the surface is too narrow, It becomes difficult to obtain an effective difference in the film thickness of the noble metal film between the vicinity of the recesses. On the other hand, when the average length RSm exceeds 150 μm, the interval between the plurality of recesses and projections becomes too wide, which is also effective. This is because it is difficult to obtain the difference in thickness of the noble metal film.
Further, the noble metal film may not be coated on the entire surface of the metal thin plate, but may be partially and substantially uniformly coated, for example, in a checkered pattern or a dotted pattern. It is possible to reduce contact resistance by controlling the convex part in the range. In the case where the noble metal film is partially coated, it is desirable to cover the surface of the metal thin plate with an area ratio of at least 30%.
In addition, on the surface of the metal thin plate, the convex portion covered with the noble metal film having a maximum thickness of 15 nm or more occupies 20% or more of the total convex portion. However, there is no clear difference in contact resistance in the region where the film thickness exceeds 15 nm. In addition, on the surface of the metal thin plate, it is not necessary that the film thickness of the noble metal film is 15 nm or more with respect to all the protrusions, and the protrusions covered with the noble metal film having a maximum film thickness of 15 nm or more are at least all protrusions. This is because a clear difference is not recognized in the contact resistance. However, it is desirable that the convex portions coated with the noble metal film having a maximum film thickness of 15 nm or more are averagely and uniformly distributed in all convex portions located on the surface of the metal thin plate.

  According to the base material for a metal separator, the surface roughness Rz (1 to 10 μm) and the average length RSm (20 to 150 μm) of the contour curve element on the surface of the metal thin plate constituting the base of the base material. An unevenness that is a range is formed, and the noble metal film is coated relatively thickly in the vicinity of the convex portion than other portions. In addition, on the surface of the metal thin plate, the convex portion having the maximum film thickness of 15 nm or more occupies 20% or more of the total convex portion. Therefore, when the surface of the metal separator formed by press-molding the base material is brought into contact with the anode electrode or the cathode electrode spotted on the both side surfaces of the solid polymer membrane of the fuel cell, Since the coated relatively thick noble metal film is preferentially contacted, the contact resistance with each electrode can be reduced. Therefore, it becomes a metal separator substrate having low contact resistance and relatively low cost.

The metal thin plate includes Fe—Cr alloy (for example, ferritic stainless steel), Fe—Ni alloy, Fe—Ni—Cr alloy (for example, austenitic stainless steel), and the like.
Further, the surface having the convex portion may be provided only on one surface in contact with the electrode in the metal thin plate, or may be provided on both the front and back surfaces.
Furthermore, the said convex part points out the part higher than the center of the average line at the peak side defined by JIS: B0601. The noble metal film having the maximum film thickness at the protrusions refers to the noble metal film having the maximum film thickness among the protrusions covered. On the other hand, the average film thickness refers to the film thickness of the noble metal when an area of a diameter of 1.8 mm on the surface is measured with fluorescent X-rays.
The “surface roughness Rz” and the “average length RSm of contour curve elements” are one of the surface property parameters defined in JIS: B0601.
Furthermore, the noble metal film is made of any one of Au, Pd, Pt, Ag, and Ru, or is made of two or more of these alloys.

  Moreover, the manufacturing method (Claim 2) of the base material for metal separators by this invention has surface roughness Rz 1-10 micrometers with respect to the surface of a metal thin plate, and the average length RSm of a contour curve element is 20-. It includes a surface forming step for providing 150 μm unevenness, and a surface treatment step for coating a noble metal film on the surface provided with the unevenness.

According to this, since the unevenness having the surface roughness Rz and the average length RSm is formed on the surface of the metal thin plate, and the surface of the unevenness is relatively uniformly coated, the metal separator base The material can be manufactured efficiently and at a relatively low cost.
In the surface forming step, the metal thin plate is passed between a roll having a surface roughness Rz and an unevenness of the average length RSm of the contour curve element on the peripheral surface and a flat roll, or the peripheral surface is uneven. In addition to being transferred between a pair of rolls on which the film is formed, the emery paper is pressed against the surface of the thin metal plate and polished.
The surface treatment step is performed by physical vapor deposition (PVD: vacuum vapor deposition, sputtering, ion plating) or electrolytic plating.

Furthermore, the present invention includes a metal separator (Claim 3) formed by press-molding the base material for a metal separator to form a plurality of reaction gas channels.
According to this, when the surface having the unevenness and the noble metal film in the metal separator is brought into contact with the anode electrode or the cathode electrode that is spotted on both sides of the solid polymer film of the fuel cell, A relatively thick noble metal film coated in the vicinity of the portion contacts with priority. Therefore, the contact resistance between the metal separator and each electrode can be reduced. Therefore, it is possible to contribute to improving the performance of the fuel cell.

The front view which shows the metal separator of one form by this invention. The front view which shows the metal separator of a different form. FIG. 3 is a schematic cross-sectional view taken along line XX in FIGS. 1 and 2. FIG. 4 is an enlarged view of an alternate long and short dash line portion Y in FIG. 3 and a partial view of a metal separator substrate of the present invention. The partial schematic diagram which shows the metal thin plate for obtaining the said base material for metal separators. Schematic which shows one manufacturing process of the said base material for metal separators. Schematic which shows one manufacturing process of the said base material for metal separators following FIG. Schematic which shows one manufacturing process of the said base material for metal separators following FIG. Schematic which shows the fuel cell obtained using the said metal separator.

Hereinafter, modes for carrying out the present invention will be described.
FIG. 1 is a front view showing one embodiment of a metal separator 1a according to the present invention.
The metal separator 1a is mainly composed of, for example, a metal thin plate 2 made of stainless steel (SUS316L, SUS304L) having a thickness of about 0.1 mm. As shown in FIG. On the front surface 3, a plurality of concave grooves (reaction gas flow paths) 4 to be a reaction gas flow path, which will be described later, are formed in parallel on the inner peripheral part excluding the peripheral part. The metal separator 1a is obtained by press-molding a flat metal separator substrate 1 described later.

In FIG. 1, an independent elongated ridge 5 protrudes between the right and left concave grooves 4 and 4, and a diversion groove 6 or a merging groove is provided above and below the plurality of concave grooves 4. The grooves 6 are individually formed. A recess 7 having a supply hole 8 at its center is communicated with the upper left portion of the diversion groove 6 via a bottleneck, and a discharge hole 9 is provided at the center of the lower right of the merge groove 6 via a bottleneck. The recess 7 is in communication. The concave grooves 4, the ridges 5, the diversion / merging grooves 6, and the dents 7 are formed by press-molding the metal thin plate, for example. The width of the groove 4 and the width of the ridge 5 may be substantially the same.
As shown by the arrow in FIG. 1, the reaction gas introduced from the supply hole 8 of the upper left recess 7 flows through the diverting groove 6, the plurality of recessed grooves 4, and the merging groove 6, and then the lower right It is discharged from the discharge hole 9 of the recess 7 to the outside.

  FIG. 2 shows a front view of a metal separator 1b of a different form. In the surface 3 of the rectangular metal thin plate 2 similar to the above, a plurality of recesses that serve as a reaction gas flow path, which will be described later, are formed on the inner peripheral portion excluding the peripheral portion. Grooves (reactive gas flow paths) 14 are formed in parallel. The metal separator 1b is also formed by press-molding a flat metal separator substrate 1 described later. In FIG. 2, between the concave grooves 14, 14 adjacent to the left and right, elongated ridges 15 projecting forward are formed in parallel, and the top surfaces of the adjacent ridges 15, 15 alternately have upper ends or lower ends. It is connected with the flat part of the surface 3 of the metal thin plate 2 as flush. As shown in FIG. 2, a substantially semicircular U-turn groove 16 is continuously formed at the upper end or lower end of the concave grooves 14, 14 adjacent to the left and right.

A substantially semicircular groove end 12 is located at the upper end of the concave groove 14 located at the left end in FIG. 2, and a supply hole 18 is perforated at the center thereof. The concave groove 14 located at the right end in FIG. A substantially semicircular groove end 17 is located at the lower end of the tube, and a discharge hole 19 is formed in the center thereof. The width of the groove 14 and the width of the ridge 15 may be substantially the same.
As indicated by the arrows in FIG. 2, the reaction gas introduced from the supply hole 18 at the groove end 12 flows in a substantially zigzag manner through the plurality of concave grooves 14 and the plurality of U-turn grooves 16, and then the discharge hole at the groove end 17. 19 is discharged to the outside.

FIG. 3 is a cross-sectional view taken along line XX in FIG. 1 and FIG.
As shown in FIG. 3, the plurality of concave grooves 4 (14) and the plurality of convex strips 5 (15) are alternately formed on the surface 3 of the metal thin plate 2 of the metal separators 1a and 1b. For this reason, the back surface (front surface) 3a of the base plate 2 has a groove 4a (14a) substantially similar to the groove 4 (14) and a groove 5a (similar to the protrusion 5 (15) ( 15) are located alternately.
The width of the groove 4 (14) and the width of the ridge 5 (15) may be substantially the same, and the groove 3 (14) and the convex of the cross section are formed on the back surface 3a of the base plate 2 in this form. The strips 4a (14a), the strips 5 (15), and the concave grooves 5a (15) having a substantially cross section are formed alternately.

4 is a schematic cross-sectional view in which the one-dot chain line portion Y in FIG. 3 is partially enlarged, and a part of the metal separator substrate 1 which is a flat plate before being press-formed into the metal separators 1a and 1b. Indicates.
As shown in FIG. 4, the metal separator substrate 1 includes the same metal thin plate 2 and an Au (noble metal) film 20 that is coated on the surface 3 and has an average film thickness of 10 nm or less.
The surface 3 of the metal thin plate 2 has projections 3h and recesses 3v alternately arranged, and has irregularities having an inclined portion 3n therebetween. The unevenness of the surface 3 has a surface roughness Rz of 1 to 10 μm, and an average length RSm of contour curve elements (between the tops of adjacent convex portions 3h and 3h on the surface 3) is in the range of 20 to 150 μm. is there.

The average length RSm is one of the lateral parameters of the surface texture, and is illustrated between the adjacent convex portions 3h and 3h in FIG. The average value of the interval (pitch) between the convex portions 3h or the concave portions 3v.
On the uneven surface 3, as shown in FIG. 4, an Au (noble metal) film 20 having an average film thickness of 10 nm or less is coated along the uneven surface 3. Among the Au films 20, among the Au films 20 a covering the convex portions 3 h, the thickest maximum film thickness is Xt, and the film thickness Xt is 15 nm or more. On the other hand, the film thickness Yt of the Au film 20b covering the recess 3v and the film thickness of the Au film 20c in the inclined part are less than 15 nm.

  As described above, the metal separator substrate 1 has the surface roughness Rz of the surface 3 of 1 to 10 μm and the thin metal plate 2 having an average length RSm of the contour curve element of the surface 3 of 20 to 150 μm. The Au film 20 having an average film thickness of 10 nm or less coated on the surface 3 of the metal thin plate 2 is provided. Moreover, among the Au film 20, the maximum film thickness Xt of the Au film 20 covering the convex portion 3h of the surface 3 is 15 nm or more. Therefore, when the surfaces 3 of the metal separators 1a and 1b obtained by pressing the substrate 1 are brought into contact with the electrodes of the fuel cell, they are relatively thickly covered with the respective convex portions 3h of the surface 3 ( Since the Au film 20a having the maximum film thickness Xt) comes into contact with priority, the contact resistance with the electrode can be reduced.

Here, the manufacturing method of the said base material 1 for metal separators is demonstrated below.
In advance, by melting, forging, hot rolling, heat treatment, cold rolling / annealing stainless steel (SUS316L, SUS304L), as shown in the partial cross-sectional view of FIG. A strip-shaped metal thin plate 2 having a flat surface 3f was manufactured.
Next, as shown in FIG. 6, the metal thin plate 2 having a flat surface 3f was passed between the pair of rolls R1 and R2, and roll transfer was performed to transfer the uneven pattern formed on the peripheral surface r1 of the roll R1. (Surface formation process). On the peripheral surface r1 of the roll R1, a concavo-convex pattern having a surface roughness Rz of 1 to 10 μm and an average length RSm of the contour curve elements of 20 to 150 μm is transferred to the surface 3f of the metal thin plate 2 An uneven pattern is formed on the entire surface.

As a result, the surface 3f of the thin metal plate 2 has a surface roughness Rz of 1 to 10 μm and an average length RSm of the contour curve elements of the surface 3 of 20 to 150 μm, as shown in the partial cross-sectional view of FIG. Thus, the convex surface 3h and the concave portion 3v are alternately positioned, and the uneven surface 3 has the inclined portion 3n positioned therebetween.
In addition, the same uneven | corrugated pattern may be provided also in the surrounding surface r2 of the said roll R2, and the unevenness | corrugation similar to the above may be formed also in the back surface 3a of the metal thin plate 2. FIG.
Further, the metal thin plate 2 was immersed in an Au plating solution in an electroplating bath (not shown), and Au electrolytic plating was performed on the surface 3 of the metal thin plate 2 so that the average film thickness was 10 nm or less. (Surface treatment process).
The surface 3 of the thin metal plate 2 may be subjected to partial Au electroplating for covering a part of the separator in contact with the electrode with an Au (noble metal) film 20. Similar Au electrolytic plating may be applied.
As a result, as shown in the partial cross-sectional view of FIG. 8, an Au (noble metal) film 20 having an average film thickness of 10 nm or less was coated along the surface 3 of the metal thin plate 2. The Au film 20 was the thickest (maximum film thickness Xt) Au film 20a of 15 nm or more at the convex part 3h of the surface 3, and the film thickness of the concave part 3v and the inclined part 3n of the surface 3 was less than 15 nm.

As described above, the thickness of the Au film 20 is thicker at the convex portion 3h of the surface 3 and is thinner at the concave portion 3v. The distance from the opposing anode side electrode in the plating solution is as follows. This is presumably due to the difficulty of migration and electrodeposition of Au ions in the plating solution. In order to reliably obtain the difference in film thickness due to the Au plating, it is desirable that the current density during electrolytic Au plating be higher than usual.
As a result, the metal separator substrate 1 having the thin metal plate 2 and the Au film 20 having different thicknesses according to the unevenness of the thin metal plate 2 was obtained. The unevenness may also be formed on the back surface 3a of the metal thin plate 2, and the Au film 20 may be coated on the back surface 3a having the unevenness by the same plating as described above.
According to the manufacturing method of the metal separator substrate 1 as described above, the surface 3 having the surface roughness Rz and the average length RSm is formed on the surface 3 of the metal thin plate 2, and the surface 3 on which the unevenness is formed. , The protrusions 3h having a maximum film thickness (Xt) of the Au film 20 of 15 nm or more occupy 20% or more of the total protrusions 3h. Accordingly, the metal separator substrates 1a and 1b can be manufactured efficiently and at a relatively low cost.
In place of the roll transfer, emery paper may be pressed, or physical plating such as sputtering may be used instead of the plating.

FIG. 9 relates to fuel cells 28 and 30 using the metal separator 1a (1b).
As shown in the schematic diagram on the left side of FIG. 9, for example, an anode electrode 25 made of carbon fiber and a similar cathode electrode 26 are laminated on each side surface of the solid polymer film 24. The solid polymer film 24 is made of, for example, a fluororesin containing a sulfonic acid group.
A pair of metal separators 1 a (1 b) having the concave grooves 4 (14) and the ridges 5 (15) on both sides of the solid polymer film 24 and facing the surface 3 covered with the Au film 20. The metal separator 1a (1b) is laminated on both side surfaces of the solid polymer film 24 so as to cover the electrodes 25 and 26, as indicated by arrows in the figure. In addition, these are fixed with the bolts and nuts, etc., not shown in the periphery thereof while maintaining the above-described laminated state.

As a result, as shown in the schematic diagram in the center of FIG. 9, both side surfaces of the solid polymer film 24 having the electrodes 25 and 26 are sandwiched between the surfaces 3 and 3 of the pair of metal separators 1a (1b). A stacked unit cell (one cell) fuel cell 28 is formed.
Further, by stacking and fixing a plurality of the fuel cells 28 of the unit cells along the thickness direction, a stack type fuel cell 30 is formed as shown in the schematic diagram on the right side of FIG.
In addition, between the said recessed grooves 4 (14) of the adjacent metal separator 1a (1b) and between the recessed grooves 4 (14) of the metal separator 1a (1b) which pinched | interposed the solid polymer film 24, it is a detour which is not shown in figure. It communicates via a flow path. Further, in the metal separator 1a (1b) in which the width of the concave groove 4 (14) and the width of the ridge 5 (15) are substantially the same, the concave groove 5a (15a) on the back surface 3a side is also reactive gas. Therefore, it is possible to provide a stack type fuel cell 30 in which one metal separator 1a (1b) is sandwiched between adjacent solid polymer membranes 24, 24.

Here, the operation of the fuel cell 28 of the unit cell will be described as an example.
In the center of FIG. 9, the fuel gas, for example, hydrogen flowing through the concave groove 4 (14) of the metal separator 1a (1b) on the left side comes into contact with the adjacent anode electrode 25 on the solid polymer film 24 side to form hydrogen ions and electrons. And decomposed. Such electrons are generated when passing through an external circuit (not shown), and then sent to the cathode electrode 26 on the opposite side of the solid polymer film 25.
On the other hand, when the oxidant gas, for example, air, flowing through the concave groove 4 (14) of the metal separator 1a (1b) on the right side in the center of FIG. The hydrogen ions penetrating 24 and the electrons react to form water. Such water is immediately drained to the outside.
The current generated when the above reactive gas such as hydrogen or air flows through the concave groove 4 (14) of the metal separator 1a (1b) is the thick Au of the convex portion 3h on the surface 3 of the convex strip 5 (15). The adjacent electrodes 25 and 26 are reliably energized through the film 20a. Therefore, according to the fuel cell 28, stable power generation can be performed. The same applies to the stack type fuel cell 30.

Here, the specific Example of the base material 1 for metal separators of this invention is demonstrated.
As shown in the table, a plurality of thin metal plates 2 made of SUS316L or SUS304L and having a thickness of 0.1 mm were prepared in advance.
Next, a pair of flat front surfaces (back surfaces) 3f of these thin metal plates 2 are subjected to surface polishing that presses emery paper of count # 400, or roll transfer by the pair of rolls R1 and R2, as shown in Table 1. Thus, the surface 3 which consists of unevenness | corrugation of surface roughness Rz and the average length RSm of a contour curve element was formed. In addition, the said surface formation process was given with respect to the metal thin plate 2 for every example shown in Table 1. FIG.
Next, as shown in Table 1, electrolytic Au plating for each average film thickness was applied to the front surface 3 and the rear surface 3a of the thin metal plate 2 for each example to coat the Au film 20, respectively.
Normally, the current density in electrolytic Au plating is 1.5 A / dm 2, but a current density of 2.5 A / dm 2 or more is desirable in order to reliably obtain a difference in film thickness of the Au film. Here, the current density in the electrolytic Au plating for each example is set to normal 1.5 A / dm 2 and higher than 3 A / dm 2 or 5 A / dm 2, and is shown in Table 1.
In the Au film 20 for each example, the average film thickness of the Au film 20a on the front surface 3 and the back surface 3a and the maximum film thickness Xt at the convex portion 3h were measured, and these are shown in Table 1.

  Further, in each example, one thin metal plate 2 having a surface 3, 3a covered with an Au film 20 is formed into a disk shape having a diameter of 20 mm, and this is inserted inside a ring-shaped insulating paper. The carbon cloth and the Au electrode were arranged symmetrically, and a pair of Au electrodes positioned on the outermost side were sandwiched between the load cells. With a load (0.98 MPa) applied between the load cells, a current generator is connected to a pair of Au electrodes, and the Au electrodes, carbon cloth, the metal thin plate 2, the carbon cloth, and the Au electrodes While energizing, a voltage measuring device was placed between a pair of Au electrodes (contact resistance test). The contact resistance value ρs (mΩ · cm 2) for each example was calculated based on the current, voltage, and the area of the surface 3 of the thin metal plate 2, and the values are shown in Table 1.

Regarding the contact resistance value ρs of each example, 10 mΩ · cm 2 or less was evaluated as ○ (good), and more than 10 mΩ · cm 2 was evaluated as x (bad), and entered in Table 1.
According to Table 1, the metal separator base material 1 of the thin metal plate 2 coated with the Au film 20 whose thickness varies on the uneven surfaces 3 and 3a of Examples 1 to 8 has all the contact resistance values ρs. It was 10 Ω · cm 2 or less (less than).
As a result, the metal separator substrate 1 of Examples 1 to 8 has a surface roughness Rz on the surfaces 3 and 3a in the range of 1 to 10 μm, and the average length RSm of the contour curve elements is 20 to 150 μm. Since the maximum film thickness Xt at the convex portion 3h is 15 nm or more, it is estimated that the current sufficiently flows through the thick Au film 20a of the convex portion 3h.

On the other hand, the metal thin plates 2 of Comparative Examples 1 to 8 all had contact resistance values ρs exceeding 10 mΩ · cm 2.
As a result, the metal thin plates 2 of Comparative Examples 3, 4, 6 and 8 are out of the range of the surface roughness Rz of 1 to 10 μm, and the metal thin plates 2 of Comparative Examples 2 and 4 are contour curve elements. The average length RSm was out of the range of 20 to 150 μm. Moreover, the thin metal plates 2 of Comparative Examples 1 to 4 and 6 to 8 were outside the range of 15 nm or more of the maximum film thickness Xt. Furthermore, in the metal thin plates 2 of Comparative Examples 1 to 8, the ratio of the convex portions 3h covered with the Au film with the maximum film thickness Xt was less than 20% in terms of the ratio to the total convex portions 3h of the surface 3. .

As a result, the convex portion 3h of the surfaces 3 and 3a is covered with a slightly thin Au film 20a, there is a void inside the Au film 20, and the convex portion 3h covered with the Au film 20 having the maximum film thickness Xt. It is presumed that the contact resistance was increased because the area of the area was too small. In Comparative Examples 5 and 7, it is presumed that the low current density during plating was also affected.
The effects of the present invention are confirmed by the metal separator substrate 1 of Examples 1 to 8 as described above, and the effects of the metal separators 1a and 1b obtained by press-molding the substrate 1 are also easily obtained. Understood.

The present invention is not limited to the embodiments and examples described above.
For example, a steel type other than the stainless steel may be applied to the thin metal plate 2.
Moreover, in order to form the said surface 3 which has an unevenness | corrugation in the metal thin plate 2, it is good also by the method of giving sandblasting or shot blasting on predetermined conditions.
Furthermore, the base material for metal separator and the metal separator of the present invention can be applied to fuel cells other than the solid polymer type (for example, phosphoric acid type fuel cells).

  Since the metal separator base material, the manufacturing method thereof, and the metal separator of the present invention have a low contact resistance with the electrode, they can be used at low cost as a metal separator such as a polymer electrolyte fuel cell and its material.

1 ... Base material for metal separator 1a, 1b ... Metal separator 2 ......... Metal thin plate 3 ...... Surface 3h ......... Protrusions 4,14 ... Concave groove (reaction gas Flow path)
20 …… Au film (noble metal film)
Xt …… Maximum film thickness at the convex part

Claims (3)

A thin metal plate having a surface in contact with the electrode of the fuel cell, the surface roughness Rz of the surface being 1 to 10 μm, and the average length RSm of the contour curve element of the surface being 20 to 150 μm;
A noble metal film having an average film thickness of 10 nm or less coated on the surface of the metal thin plate,
On the surface of the thin metal plate, the convex portions covered with the noble metal film having a maximum film thickness of 15 nm or more occupy 20% or more of the convex portions on the entire surface.
A metal separator substrate characterized by the above. A surface forming step for providing irregularities having a surface roughness Rz of 1 to 10 μm and an average length RSm of the contour curve element of 20 to 150 μm with respect to the surface of the metal thin plate;
A surface treatment step of coating the noble metal film on the surface provided with the irregularities,
The manufacturing method of the base material for metal separators characterized by the above-mentioned. The metal separator substrate according to claim 1 is press-molded to form a plurality of reactive gas flow paths.
A metal separator characterized by that.

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