JP5204182B2 - Manufacturing method of fuel cell separator - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for producing a fuel cell separator, and more particularly to a method for producing a fuel cell separator having improved durability by improving the adhesion between a separator substrate and a resin coating layer.

  For example, in a polymer electrolyte fuel cell, as shown in FIG. 10, a joined body (MEA: Membrane Electrode) in which an electrolyte membrane 52 made of a solid polymer membrane is sandwiched between two electrodes, a fuel electrode 50 and an air electrode 54. Assembly) is a minimum unit of a cell sandwiched between two separators 40, and usually a plurality of cells are stacked to form a fuel cell stack (FC stack) to obtain a high voltage.

The power generation mechanism of the polymer electrolyte fuel cell generally includes a fuel gas (anode side electrode) 50 containing a fuel gas, such as a hydrogen-containing gas, and an air electrode (cathode side electrode) 54 containing an oxidant gas such as a main gas. Is supplied with gas or air containing oxygen (O ₂ ). The hydrogen-containing gas is supplied to the fuel electrode 50 through fine grooves processed on the surface of the separator 40, and is decomposed into electrons and hydrogen ions (H ⁺ ) by the action of the catalyst of the electrode. The electrons move from the fuel electrode 50 to the air electrode 54 through an external circuit, and produce an electric current. On the other hand, hydrogen ions (H ⁺ ) pass through the electrolyte membrane 52 to reach the air electrode 54 and combine with oxygen and electrons that have passed through the external circuit to become reaction water (H ₂ O).

  Furthermore, the two separators that sandwich the MEA described above are partition plates that serve to separate hydrogen gas and oxygen gas, and also have a function of electrically connecting the stacked cells in series. In addition, fine concave and convex grooves are formed on the surfaces of the two separators, and these grooves serve as gas flow passages through which the hydrogen-containing gas and the oxygen-containing gas or air are circulated.

  An example of a conventional cell structure is shown in FIGS. FIG. 11 shows a cross section taken along the line A-A ′ of FIG.

  As shown in FIGS. 11 and 12, supply communication holes 12a, 12b, and 12c to which fuel gas, oxidant gas, and cooling water are supplied and fuel gas and oxidation are provided at both ends of the two separators 110 and 120, respectively. Discharge communication holes 14a, 14b, and 14c for discharging the agent gas and the cooling water are provided, and further, the fuel gas and the oxidant gas supplied from the supply communication holes 12a and 12b are circulated through the separators 110 and 120, respectively. Gas flow paths 152 and 154 are provided. In addition, concave portions 106 and 116 are provided on the opposing surfaces of the separators 110 and 120, respectively, and seal materials 60a and 60b for separating the fuel gas and the oxidant gas are provided on both peripheral edges of the MEA 30, which is a joined body. The sealing materials 60a and 60b are bonded to the two separators 110 and 120 by adhesive materials 70a and 70b, respectively, to form cells.

  When stainless steel (so-called SUS) is used as the separator, a passive film 22 made of a chromium oxide film is formed on the surface of the SUS separator substrate 20 as shown in FIG. On the other hand, the above-mentioned adhesive and sealing material tend to use environmentally friendly materials in recent years. For example, there is a tendency to use a highly hydrophilic aqueous resin from a lipophilic resin soluble in a conventional solvent. . However, the passive film 22 has a low affinity with the aqueous resin. Therefore, when the water-based resin is bonded directly on the SUS separator base material 20 as an adhesive or as a sealing material without using an adhesive, the adhesion is weak, and the fuel sandwiched the bonded body between a pair of separators. When battery cells are stacked in stacks and pressure is applied at the manifold and the stack is tightened, shear stress occurs and the resin peels off, or the resin peels off due to other factors such as thermal expansion during use. In some cases, resin desorption may occur.

  As shown in FIG. 13, when an aqueous resin is formed by electrodeposition coating on a SUS separator base material 20 on which a passive film 22 made of a chromium oxide film is formed, the non-reactivity is shown in FIG. The affinity between the kinetic film 22 and the obtained aqueous resin layer 26 is low. As a result, air is entrained when the SUS separator substrate 20 is immersed in the bath of the electrodeposition paint, and as shown in FIG. Electrodeposition coating is performed with the bubbles 23 remaining on the surface of the separator substrate 20 made of the product, and a large number of pinholes 27 having a diameter of 50 μm to 100 μm are generated in the formed aqueous resin layer 26.

  Therefore, an iron-based hydrated oxide film having high affinity with both is provided between the passive film formed on the surface of the separator substrate made of SUS and the aqueous resin layer. It is proposed that a passive film and an aqueous resin layer are adhered to each other to form a fuel cell separator having high adhesion between a SUS separator substrate and an aqueous resin layer (for example, Patent Document 1). reference).

  Also, an antifoaming agent is attached to the surface of the object to be coated before electrodeposition coating to reduce air entrainment when the object is immersed in the bath of electrodeposition paint, and bubbles on the surface of the object to be coated in the bath An electrodeposition coating method has been proposed that suppresses adhesion, thereby preventing local non-adhesion of the electrodeposition paint and suppressing the occurrence of film defects such as pinholes in the electrodeposition coating film (for example, (See Patent Document 2).

  Further, Patent Document 3 discloses a wafer plating method in which, when a plating process is performed on a wafer surface as a base material, the wafer is wetted with water or water containing a surfactant and then immersed in a plating solution to perform the plating process. It is disclosed.

JP 2007-242576 A JP 2007-84877 A Japanese Patent Laid-Open No. 2004-59985

  In recent years, with increasing demand for fuel cells, it is desired to improve the durability of fuel cells.

  The present invention has been made in view of the above problems, and an iron-based hydrated oxide film having high adhesion to a resin layer is previously formed on a separator substrate, and further, an iron-based hydrated oxide film and a resin layer are formed. In order to improve the wettability, the surface of the iron-based hydrated oxide film is treated with water before forming the resin layer, and then the resin layer is formed on the iron-based hydrated oxide film. A manufacturing method for manufacturing a fuel cell separator is provided.

  The manufacturing method of the fuel cell separator of the present invention has the following characteristics.

(1) The peripheral surface of each of the pair of separator base materials made of stainless steel, excluding the gas flow paths, is subjected to cathodic electrolysis in an alkaline solution, and iron-based hydration oxidation is performed on the peripheral surface of the pair of separator base materials. A step of forming a physical film, a step of performing water treatment to wet the surface of the iron-based hydrated oxide film with water and temporarily forming a water treatment layer composed of a water film on the surface, and the pair of separator base materials An iron-based hydration in which at least one separator base material, which is temporarily formed with a water treatment layer made of the water film, is immersed in an electrodeposition bath, and the water treatment layer is temporarily formed. And a step of electrodepositing an electrocoating material containing an aqueous resin on the oxide film.

  (2) In the method for producing a separator for a fuel cell according to (1) above, in the water treatment step, the surface of the iron-based hydrated oxide film is wetted with water for 1 to 5 minutes, A method for producing a separator for a fuel cell, characterized in that a water treatment layer is temporarily formed.

  Since the iron-based hydrated oxide film formed by cathodic electrolysis in an alkaline solution is formed on the passive film present on the surface of the separator base made of stainless steel, the electrolytically treated separator base It is possible to maintain the anticorrosion property of the separator substrate before treatment. Furthermore, since the composition of the iron-based hydrated oxide film and the passive film on the separator substrate are close to each other, the adhesiveness is high due to metal bonding. In addition, by providing a water treatment step that wets the surface of the iron-based hydrated oxide film with water, the wettability between the surface of the iron-based hydrated oxide film and the electrocoating material containing an aqueous resin increases. As a result, even if the separator substrate is immersed in an electrocoating material bath containing an aqueous resin, bubbles are less likely to adhere to the surface of the iron-based hydrated oxide film formed on the separator substrate. By electrocoating an electrocoating material containing an aqueous resin uniformly on the surface of the hydrated oxide film, the aqueous resin can be deposited, and the generation of pinholes due to bubble marks can be suppressed or prevented. Furthermore, since the iron-based hydrated oxide film can be bonded to the hydrophilic functional group of the aqueous resin forming the resin layer formed thereon, for example, by hydrogen bonding, the iron-based hydrated oxide film Adhesiveness to the resin layer is also high. Therefore, even if shear stress occurs when stacking the fuel cell, stacking of the resin can be prevented, and even if other thermal expansion occurs during use, the resin and the separator base can be prevented. Since the adhesiveness with the material is high, there is no possibility that the resin is peeled off or detached. Thereby, the sealing effect between the separators by the resin layer is further improved, and the durability of the obtained fuel cell is further improved.

(3) In the method for manufacturing a fuel cell separator according to (1) or (2), the alkaline solution is an electrolytic treatment solution, and the electrolytic treatment solution is a 5 to 50 mass% sodium hydroxide solution. Or an aqueous solution obtained by adding 0.2 to 20% by mass of trisodium phosphate 12-hydrate and 0.2 to 20% by mass of sodium carbonate as a buffering agent to a 5 to 50% by mass sodium hydroxide solution. This is a method for producing a fuel cell separator having a temperature of 20 ° C. to 95 ° C., a current density of 0.5 A / dm ² or more, and a treatment time of 10 seconds or more.

  By performing cathodic electrolysis under the above conditions, a uniform iron-based hydrated oxide film can be formed.

  (4) The method for manufacturing a fuel cell separator according to any one of (1) to (3), wherein the water is ion-exchanged water.

  Impurities are brought into the bath of the electrocoating material through the separator substrate, and further, impurities can be prevented from accumulating in the bath, so that stable electrodeposition coating can be performed over time.

  (5) The method for producing a fuel cell separator according to any one of (1) to (4) above, wherein the aqueous resin contains a polyamide-based resin.

  Since the polyamide-based resin has an amide group that is an affinity functional group, the affinity of the iron-based hydrated oxide film formed on the separator substrate is high. As a result, the iron-based water on the separator substrate is high. Adhesiveness with Japanese oxide film is also high. In particular, since the iron-based hydrated oxide film has a mixed composition of iron hydroxide and oxide, many hydroxyl groups capable of hydrogen bonding with amide groups in the polyamide-based resin are scattered on the surface. To do. Therefore, the polyamide-based electrodeposition resin is easy to become familiar with the iron-based hydrated oxide film on the separator substrate, and can form a resin layer with a uniform thickness. In addition, the sealing effect of the separator can be obtained.

  According to the present invention, it is possible to suppress or prevent the formation of bubble marks in the aqueous resin layer obtained by electrodeposition coating, and because the adhesiveness between the separators is high through the resin layer, It is possible to provide a highly durable fuel cell with excellent anticorrosion properties.

It is process drawing which shows an example of the process of the manufacturing method of the separator for fuel cells of this invention. It is a figure for demonstrating the cathode electrolysis process area | region of the separator for fuel cells of this invention. It is a figure explaining the water treatment process by the shower water washing of the manufacturing method of the separator for fuel cells of this invention. It is a figure explaining the water treatment process using the immersion water tank of the manufacturing method of the separator for fuel cells of the present invention. It is a schematic diagram explaining the adhesive force of the iron-type hydrated oxide membrane | film | coat and aqueous resin layer in the separator for fuel cells of this invention. It is a schematic diagram explaining the adhesive force of the SUS surface and aqueous resin layer in the conventional separator for fuel cells. It is a schematic diagram explaining the mechanism in which a pinhole generate | occur | produces in an aqueous resin layer. It is a schematic diagram explaining the bubble non-residual mechanism by forming a water treatment layer. It is the schematic explaining an example of the pinhole detection method in an aqueous resin layer. It is a figure explaining the structure of the cell of a fuel cell, and the mechanism at the time of electric power generation. It is sectional drawing explaining the structure of the one aspect | mode of the conventional cell for fuel cells. It is a figure explaining the position of the sealing material adhere | attached on the separator in the cell for the conventional fuel cell. It is a figure explaining the pinhole generation | occurrence | production of the resin layer surface at the time of forming an aqueous resin layer by direct electrodeposition coating on the SUS separator base material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Manufacturing method of fuel cell separator]
A fuel cell separator according to a preferred embodiment of the present invention will be described below.

  As shown in FIG. 1, the manufacturing method of the separator for a fuel cell in the present embodiment is such that the peripheral surface of each of the pair of separator base members made of stainless steel excluding the gas flow paths is subjected to cathodic electrolysis treatment in an alkaline solution. Performing a step of forming an iron-based hydrated oxide film on the peripheral surface of the pair of separator base materials (S200) and a step of performing a water treatment of wetting the surface of the iron-based hydrated oxide film with water (S202) ), Electrodepositing an electrocoating material containing an aqueous resin on the water-treated iron-based hydrated oxide film of at least one of the pair of separator base materials (S204), and optionally water-based And a resin baking step (S206).

  Below, each process of the manufacturing method of the separator for fuel cells of this Embodiment is demonstrated in detail using FIGS. 2-8.

  First, the process of forming the iron-based hydrated oxide film (S200 in FIG. 1) will be described. As the separator substrate 20 made of SUS shown in FIG. 2, for example, austenitic stainless steel such as SUS304, SUS305, SUS310, SUS316, and SUSMX7, ferritic stainless steel such as SUS430, martensitic stainless steel such as SUS403, SUS410, SUS416, and SUS420, and the like. , Stainless steel such as precipitation hardened stainless steel such as SUS631.

  In the present embodiment, as shown in FIG. 2, supply communication holes 12a, 12b, and 12c to which fuel gas, oxidant gas, and cooling water are supplied and fuel gas are provided at both ends of the SUS separator substrate 20, respectively. In addition, exhaust communication holes 14a, 14b, and 14c through which the oxidant gas and cooling water are discharged are provided, and the SUS separator base material 20 is provided with fuel gas and oxidant gas supplied from the supply communication holes 12a and 12b. Are provided with gas channels 152 and 154 of concave and convex grooves that respectively circulate.

  In the present embodiment, the peripheral portion 28 of the SUS separator 20 excluding the masked gas flow paths 152 and 154, that is, the supply communication holes 12a, 12b, and 12c to which fuel gas, oxidant gas, and cooling water are supplied. In addition, an iron-based hydrated oxide film is formed by cathodic electrolysis at the peripheral ends of the discharge communication holes 14a, 14b, and 14c from which the fuel gas, the oxidant gas, and the cooling water are discharged, and the seal region for the separator coupling. . This iron-based hydrated oxide film comprises a mixture of iron hydroxide and iron oxide, and forms an iron-based hydrated oxide film (S200 in FIG. 1, hereinafter referred to as “superhydrophilic treatment”). As described later, this is a treatment for bonding a hydroxyl group (OH group) to iron and chromium. In the obtained electrolytically treated separator 100, as shown in FIG. 2, an iron-based hydrated oxide film 24 is formed on the peripheral edge excluding the gas flow paths 152 and 154.

  In the masking, a substantially rectangular seal film that prevents permeation of the electrolytic solution may be detachably bonded onto the gas flow path of the SUS separator substrate 20. Alternatively, a conventional masking method such as applying an insulating resin on the gas flow path of the SUS separator substrate 20 and solidifying it can be used.

  The cathode electrolytic treatment of the present embodiment is made of the SUS separator base material 20 by connecting the electrode connecting portion 15 of the SUS separator base material 20 shown in FIG. An iron-based hydrated oxide film having a predetermined thickness is formed using a workpiece as a cathode and iron or the above-described stainless steel as an anode. In addition, when using stainless steel as an anode, the ferritic stainless steel whose nickel content is less than 3 mass% is preferable.

The condition of the cathodic electrolysis is that the alkaline solution is an electrolysis solution, and the electrolysis solution is buffered in a 5 to 50 mass% sodium hydroxide solution or a 5 to 50 mass% sodium hydroxide solution. A buffer aqueous solution containing 0.2 to 20% by mass of trisodium phosphate 12-hydrate and 0.2 to 20% by mass of sodium carbonate as an agent. dm ² or more and a processing time of 10 seconds or more.

The reason why the range of the above conditions is preferable is as follows. That is, less than 5% by weight of sodium hydroxide, less than 0.2% by weight of trisodium phosphate 12 hydrate, and less than 0.2% by weight of sodium carbonate are uniformly effective iron on the surface of the SUS separator substrate 20. It is difficult to obtain a system hydrated oxide film, and there is a possibility that the adhesion with a later aqueous resin will be lowered. Further, sodium hydroxide exceeding 50% by mass, trisodium phosphate 12 hydrate exceeding 20% by mass, and sodium carbonate exceeding 20% by mass are remarkably deteriorated in electrolytic solution and economically disadvantageous. Further, when the liquid temperature is less than 20 ° C., the formation of the iron-based hydrated oxide film becomes insufficient, while when it exceeds 95 ° C., the formation time of the iron-based hydrated oxide film is shortened, Although power consumption is reduced, it is difficult to control the concentration of the electrolytic solution, and in some cases, a non-uniform film may be formed. In addition, when the current density is less than 0.5 A / dm ² and the treatment time is less than 10 seconds, the formation of the iron-based hydrated oxide film becomes insufficient, and there is a possibility that the adhesiveness with the aqueous resin later deteriorates. .

  In the cathodic electrolysis treatment of the present embodiment, the reason for masking the gas flow path region of the separator substrate is as follows. If the cathodic electrolysis is performed without performing the above-described masking, an iron-based hydrated oxide film is also formed in the gas channel region of the separator substrate. On the other hand, as described above, a fuel cell is formed by sandwiching a joined body between a pair of separators, and this fuel cell is further stacked to form a fuel cell. When using this fuel cell, if fuel gas or oxidant gas is circulated through the gas flow path, iron hydroxide or iron oxide is converted from the iron-based hydrated oxide film formed in the gas flow path basin to a high solid content. There is a possibility that the electrolyte membrane made of a molecular membrane is gradually eluted into a joined body sandwiched between two electrodes, a fuel electrode and an air electrode, and the fuel cell is deteriorated. Therefore, in the present embodiment, the gas channel region of the separator base material is masked so that the iron-based hydrated oxide film is not formed during the cathode electrolysis treatment.

  Moreover, in this Embodiment, the cathode electrolysis process is performed by making into a cathode the workpiece | work which consists of the SUS separator base material 20 in an alkaline solution. Therefore, as shown in FIG. 5, the iron-based hydrated oxide film 24 is formed on a passive film 22 made of a chromium oxide film on the surface of the SUS separator substrate 20. The iron-based hydrated oxide film 24 has a maximum thickness of 10 nm. Further, as shown in FIG. 5, the iron-based hydrated oxide film 24 formed by the cathodic electrolysis in the alkaline solution described above is formed on the passive film 22 existing on the surface of the SUS separator substrate 20. In addition, since the hydroxyl group (OH group) is bonded to iron and chromium, the electrolytically treated separator base material 100 (see FIG. 2) further maintains the corrosion resistance of the SUS separator base material 20 before treatment. The iron-based hydrated oxide film 24 and the passive film 22 on the separator substrate are close in composition, and therefore have high adhesion due to metal bonding.

  If the separator substrate 20 made of SUS is subjected to electrolytic treatment with an alkaline solution as an anode, the passive film formed on the separator substrate 20 made of SUS is eluted, and further, iron in SUS is eluted and oxidized. An iron film will be formed. In such a case, since the passive film has disappeared, the anticorrosion property is likely to deteriorate. In addition, when electrolytic treatment is performed with an acidic solution using a SUS separator substrate as an anode, the passive film is also eluted, and chromium in SUS is further eluted to form a chromium oxide film. In such a case, the chromium oxide film is a passive film and thus has anticorrosion properties, but the wettability with respect to the aqueous resin remains poor. Therefore, in the present embodiment, it is preferable to perform electrolytic treatment with an alkaline solution using the SUS separator substrate 20 as a cathode.

  Next, the electrolytically treated separator base in which the masking material 29 is applied to the back surface region opposite to the bonded body sandwiching surface of the electrolytically treated separator substrate 100 (FIG. 2) and the gas passage portion. While the material is suspended, the surface of the iron-based hydrated oxide film on the electrolytically treated separator base material is wetted with water to adjust the surface tension of the iron-based hydrated oxide film (S202 in FIG. 1). The electrocoating material contains a resin that also has hydrophilic properties. On the other hand, the iron-based hydrated oxide film is a superhydrophilic film. Therefore, as shown in FIG. 5, the wettability with the electrocoating material is improved by passing the water treatment layer 25 (so-called water film) temporarily formed on the surface of the iron-based hydrated oxide film 24. As shown in FIG. 8, when the masked electrolytically treated separator base material is immersed in the electrodeposition bath, bubbles remain on the surface of the iron-based hydrated oxide film 24 of the electrolytically treated separator base material. As a result, the electrodeposition coating described later can be suitably performed.

  Here, the water treatment step of wetting the surface with water may be a shower water washing step or a water bath immersion step, but considering the fact that it is clean water and the reduction in the amount of water used, the shower water washing step is preferred. . The water used is preferably ion-exchanged water, for example, ion-exchanged water having an electric conductivity of 10 μS / cm or less is preferred.

  An example of the apparatus structure used for the shower water washing process mentioned above is shown in FIG. As shown in FIG. 3, water is sprayed from the water injector 30 to both the bonded body sandwiching surface of the workpiece 102 on which the masking material 29 is applied and the opposite surface, and the water is sprayed on the surface of the workpiece 102. Flow (for example, in the direction of the black arrow in FIG. 3). The shower water washing time is from 1 second to 5 minutes, more preferably 60 seconds. If it is less than 1 second, the surface tension of the entire surface of the iron-based hydrated oxide film 24 of the workpiece 102 cannot be modified by water, and as a result, the workpiece 102 is immersed in a bath filled with the electrocoating material. In the same way as in the case shown in FIG. 7, the electrodeposition coating is performed while air bubbles remain on the surface of the iron-based hydrated oxide film 24 of the workpiece 102, and the formed aqueous resin layer is filled with air. , Pinholes will occur. On the other hand, when it exceeds 5 minutes, the improvement of the surface tension modification by the water flow cannot be expected any more, and the amount of water to be used increases, resulting in poor economic efficiency. Alternatively, water may be sprayed from above the work 102 suspended for half or more of a predetermined time for injecting water, and then water may be gradually sprayed downward. In such a case, even if the amount of water to be sprayed is not large, water can flow over almost the entire surface of the workpiece 102, and the wettability of the surface can be improved.

  Moreover, an example of the apparatus structure used for the water tank immersion process mentioned above in FIG. 4 is shown. As shown in FIG. 4, the workpiece 102 is immersed in the water tank 32, wetted with water on the entire surface of the iron-based hydrated oxide film of the workpiece 102, and the surface tension is adjusted. The immersion time is from 1 second to 5 minutes, more preferably 60 seconds, as in the case of shower water washing. Further, when immersed, the bubbles generated on the surface of the iron-based hydrated oxide film 24 may be separated from the surface by slowly moving the workpiece 102 up and down (in the direction of the arrow in FIG. 4).

  Next, after a water treatment step, an aqueous resin layer 26 is formed on the iron-based hydrated oxide film 24 (S204 in FIG. 1). In this case, the masking material 29 is applied to the gas flow path portion of the electrolytically treated separator base material 100 (FIG. 2) and the back surface region opposite to the joined body sandwiching surface of the electrolytically treated separator base material 100 in the same manner as described above. The resin layer is formed with the masking process applied.

  The electrolytically treated separator substrate 100 (FIG. 2) subjected to masking is used as a cathode, immersed in the electrocoating material for forming the aqueous resin layer 26, and a direct current is applied between the counter electrode and the cation electrode. An aqueous resin layer 26 is formed on the iron-based hydrated oxide film 24 by deposition. Here, the electrolytically treated separator base material 100 (FIG. 2) is a plurality of portions in the region corresponding to the back surfaces of the gas flow paths 152 and 154, or the entire surface excluding the masked region of the electrolytically treated separator base material 100. The electrode coating portion is connected to the cathode, and the electrocoating material is electrodeposited in a region other than the masking using the work made of the electrolytically treated separator substrate 100 as the cathode.

  As the electrocoating material for forming the aqueous resin layer 26, a polyamide-based resin having a hydrophilic functional group such as an amide group can be used. Examples of the polyamide-based resin include polyamide resin, polyamideimide resin, and amine-cured epoxy resin.

  Since the polyamide-based resin has an amide group that is an affinity functional group, the affinity of the iron-based hydrated oxide film 24 formed on the separator substrate is high. Adhesion with the film 24 is also high. As described above, since the iron-based hydrated oxide film 24 has a mixed composition of iron hydroxide and oxide, a hydroxyl group capable of hydrogen bonding with an amide group in the polyamide-based resin has a surface thereof. There are many. Therefore, as shown in FIG. 5, particularly, the polyamide-based electrodeposition resin is easy to be familiar with the iron-based hydrated oxide film 24 on the separator substrate, and can form the aqueous resin layer 26 with a uniform thickness. Even if the resin layer is thinner than the conventional one, the sealing effect of the separator can be sufficiently obtained.

  In addition, after the electrodeposition coating step (S204) shown in FIG. 1, the electrodeposited separator base material is transferred to a paint recovery tank, and an uncoated coating material is recovered. After washing with a water washing tank and then draining the surface of the separator substrate electrodeposited with a draining air knife, if necessary, pre-drying and removing the masking material, a predetermined temperature (for example, For example, baking is performed at 210 ° C. for 30 minutes (S206 in FIG. 1). Thereby, the separator for fuel cells of the embodiment described later is obtained.

[Fuel cell separator]
The separator for a fuel cell according to the present embodiment performs cathodic electrolysis treatment in the alkaline solution on the peripheral surface of each of the pair of separator bases made of stainless steel except for the gas flow path, and the peripheral edges of the pair of separator bases An iron-based hydrated oxide film is formed on the surface of the part, and a resin layer obtained from an electrocoating material containing an aqueous resin is formed on at least one iron-based hydrated oxide film of the one separator substrate, The number of pinholes having a diameter of 50 μm to 100 μm per 10 cm × 10 cm square unit area of the resin layer is 4 or less.

  By reducing the number of pinholes having a diameter of 50 μm to 100 μm per 10 cm × 10 cm square unit area of the resin layer to 4 or less, the sealing effect between the separators by the resin layer is further improved, and the durability of the obtained fuel cell Will be improved.

  Hereinafter, the fuel cell separator obtained by the method for producing a fuel cell separator of the present invention will be described with reference to examples. The present invention is not limited to the following examples as long as it does not exceed the gist thereof.

[Example 1]
A substantially rectangular rubber seal member having suction cups that can be attached and detached at the four corners is joined to a gas flow path region of a separator base material made of austenitic stainless steel SUS304. The masked separator substrate is used as a cathode, and a plate piece made of ferritic stainless steel SUS430 is used as an anode. An electrolytic aqueous solution of 20% by mass of sodium hydroxide, 5% by mass of trisodium phosphate 12%, and 5% by mass of sodium carbonate is used. Then, after treatment for 120 seconds at a cathode electrolysis current density of 6 A / dm ² in an aqueous electrolytic solution at 80 ° C., the substrate was washed with water and the sealing member was removed, and then the treated separator substrate was dried. The obtained electrolytically treated separator base material is referred to as “separator base material A”.

  A substantially rectangular rubber seal member (masking material 29 in FIG. 3) having suction cups that can be attached and detached at the four corners is joined to the gas flow path region of the separator base A subjected to the cathodic electrolysis treatment, and the separator A Similarly, a rubber seal member was connected to the entire back surface, which is the opposite surface to the bonded body sandwiching surface.

Next, using the shower rinsing apparatus shown in FIG. 3, the water jet 30 is used for 60 minutes in an amount of 1 L / m ² from both the bonded body sandwiching surface of the separator base A subjected to the masking treatment and the opposite surface. Water was treated by spraying ion-exchanged water having an electric conductivity of 10 μS / cm for 2 seconds.

  After that, the above masked separator base A is applied to an electrodeposition bath having a concentration of 20% by mass containing a cationic electrocoating material (“Insuled 4200” manufactured by Nippon Paint Co., Ltd.) containing an aqueous polyamideimide resin. Was immersed as a cathode, and the coating electrode ratio was adjusted to +/−: − 1/2, the distance between the electrodes: 15 cm, and the liquid temperature of 30 ° C. After increasing the applied voltage to be a predetermined voltage in 5 seconds and reaching the predetermined voltage, holding the applied voltage for 115 to 145 seconds, performing cationic electrodeposition coating, and collecting the uncoated coating material, After washing with a 4-stage immersion water washing tank, and then draining the surface of the separator substrate electrodeposited with a draining air knife, pre-drying, removing the masking material, and baking at 260 ° C. for 30 minutes The resin layer forming separator base material B was obtained.

[Example 2]
Except having replaced the separator base material A obtained in Example 1 with the water treatment by the water tank shown in FIG. 4, it carried out according to Example 1 and obtained the resin layer forming separator base material C. The capacity of ion-exchanged water electric conductivity 10 [mu] S / cm, which is stored in the water tank is 200 meters ^3, the immersion time was 60 seconds.

[Comparative Example 1]
The separator base material made of untreated austenitic stainless steel SUS304 not subjected to the electrolytic treatment in Example 1 is referred to as “separator base material D”. A substantially rectangular rubber seal member having suction cups that can be attached and detached at the four corners is joined to the gas flow path region of the separator base D, and the same is applied to the entire back surface opposite to the joined body sandwiching surface of the separator D. A rubber seal member (masking material 29 in FIG. 3) was connected to the above. After that, electrodeposition coating is performed in the same electrolytic bath as in Example 1 under the same electrodeposition coating conditions, and then similarly washed with water, drained, and pre-dried to form a resin layer to form a resin. Separator substrate E was obtained.

[Comparative Example 2]
The separator base material A obtained in Example 1 was performed according to Example 1 except that the water treatment was not performed, and a resin layer-forming separator base material F was obtained.

[Comparative Example 3]
On both sides of the separator substrate A obtained in Example 1, ethanol (Kanto Chemical Co., Ltd., special grade), which is an antifoaming agent, is injected instead of water from the water injector 30 of the shower washing apparatus shown in FIG. Except having carried out, it carried out according to Example 1 and the resin layer forming separator base material G was obtained.

<Pinhole detection of resin layer forming separator substrate>
Using the pinhole detection method shown in FIG. 9, the number of pinholes having a diameter of 50 μm to 100 μm per unit area of 10 cm × 10 cm square of the resin layer of the resin layer forming separator substrate was detected. That is, using the tester 34 (manufactured by HIOKI) shown in FIG. 9 and setting the direct current measurement with a changeover switch, the minus measurement terminal is brought into contact with the SUS separator substrate 20 side of the resin layer forming separator substrate, The absorbent cotton 36 dampened with sulfuric acid-containing pH 2.0 acidic solution + Cl ⁻ (500 ppm) is wound around the tip of the plus measurement terminal, and a voltage (25 V to 125 V) is applied between the plus measurement terminal and the minus measurement terminal. Then, a positive measuring terminal with sulfuric acid-containing absorbent cotton is applied to the surface of the aqueous resin layer 26 while being rubbed. Here, when there is a pinhole 27 in the aqueous resin layer 26, the iron hydrated oxide film 24 is exposed in the portion of the pinhole 27 in FIG. 9, and the SUS surface is exposed when the electrolytic treatment is not performed. Therefore, the sulfuric acid solution oozed out from the absorbent cotton 36 penetrates into the pinhole 27 and a corrosion current flows out. Thereby, the number of pinholes 27 per unit area was counted. The pinhole diameter was measured using a scanning electron microscope.

  The resin layer forming separator base materials B, C, E, F, and G obtained in Examples 1 and 2 and Comparative Examples 1, 2 and 3 were evaluated using the pinhole detection evaluation method described above. The results are shown in Table 1.

  The method for producing a fuel cell separator of the present invention is effective for any use as long as it uses fuel cells, but can be used particularly for a fuel cell for vehicles.

  20 SUS separator substrate, 22 passive film, 24 iron-based hydrated oxide film, 25 water treatment layer, 26 aqueous resin layer, 27 pinhole, 28 peripheral portion.

Claims (5)

The peripheral surface of each of the pair of separator base materials made of stainless steel excluding the respective gas flow paths is subjected to cathodic electrolysis in an alkaline solution, and an iron-based hydrated oxide film is formed on the peripheral surface of the pair of separator base materials. Forming, and
A step of performing water treatment to wet the surface of the iron-based hydrated oxide film with water and form a water treatment layer consisting of a water film temporarily on the surface;
At least one separator substrate of the pair of separator substrates , wherein the separator substrate on which the water treatment layer is temporarily formed of the water film is immersed in an electrodeposition bath , and the water treatment layer temporarily And a step of electrodepositing an electrocoating material containing an aqueous resin on the formed iron-based hydrated oxide film. In the manufacturing method of the separator for fuel cells of Claim 1,
In the water treatment step, the surface of the iron-based hydrated oxide film is wetted with water for 1 to 5 minutes, and a water treatment layer is temporarily formed on the surface. Manufacturing method. In the manufacturing method of the separator for fuel cells of Claim 1 or Claim 2,
The alkaline solution is an electrolytic treatment solution,
The electrolytic treatment solution is 5 to 50% by weight of sodium hydroxide solution, or 5 to 50% by weight of sodium hydroxide solution and 0.2 to 20% by weight of trisodium phosphate 12-hydrate as a buffer, 0 A method for producing a separator for a fuel cell, which is an aqueous solution to which 2 to 20% by mass of sodium carbonate is added, the liquid temperature is 20 to 95 ° C., the current density is 0.5 A / dm ² or more, and the treatment time is 10 seconds or more. In the manufacturing method of the separator for fuel cells of any one of Claims 1-3,
A method for producing a fuel cell separator, wherein the water is ion-exchanged water. In the manufacturing method of the separator for fuel cells of any one of Claims 1-4,
The manufacturing method of the separator for fuel cells in which the said aqueous resin contains the polyamide-type resin.

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