JP2005063889A - Manufacturing method of stainless steel separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the cleaning time of a stainless steel thin plate which is a separator material, reduce the quantity of a washing liquid used, suppress the treatment cost of the waste fluid, and simplify facility. <P>SOLUTION: The manufacturing method is constituted of a process in which oil is coated on a stainless steel thin plate 10 and press forming is made, a process in which the oil is removed by spraying a cleaning alkaline solution on the press forming material 14, a process in which the cleaning alkaline solution is removed by spraying service water or industrial water on the press forming material 14, a process in which the service water or the industrial water is removed by spraying ion exchange water on the press forming material 14, a process in which an alkaline solution for passivation treatment is sprayed on the press forming material 14 in order to apply passivation treatment on the press forming material 14, a process in which the alkaline solution for passivation treatment is removed by spraying ion exchange water on the passivation coating forming material 17, and a process in which the passivation coating forming material 17 is heated and dried. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a stainless steel separator for a fuel cell.

  Since the solid polymer electrolyte fuel cell has a structure in which a desired output is obtained by stacking a plurality of each fuel cell, a separator for partitioning each fuel cell is a pressure applied at the time of stacking compared to a resin material. Metallic materials that are advantageous in terms of strength against strength and downsizing after lamination are considered promising. In particular, the use of stainless steel materials has been studied because it forms a passive film having high corrosion resistance against the acidic atmosphere around the electrode portion of the cell.

As a processing method of the stainless steel material as described above, degreasing and passivation treatment (for example, see Patent Document 1), degreasing and etching (for example, see Patent Document 2), degreasing and polishing are performed. A thing (for example, refer to patent documents 3) and a thing (for example, refer to patent documents 4) which perform pickling are known.
Japanese National Patent Publication No. 10-503241 JP-A-9-291400 JP 2000-282276 A JP 2001-214286 A

  Patent Document 1 provides an alkali-based formulation that cleans and passivates the surface of a stainless steel plate, and the cleaning liquid on the surface of the stainless steel is an alkali component excluding an alkali salt such as carbonate + chelating agent + water. + Made of surfactant.

  Patent Document 2 discloses a passive film formed on a stainless steel surface while electrolytically treating an aqueous solution containing sodium hydroxide and sulfuric acid having a pH of 10 to 12.5 as an electrolyte to remove the rolling oil adhering to the surface after stainless steel cold rolling. It is intended to improve the etching property of the material by reducing the concentration of the Cr component therein.

  Patent Document 3 shows that by brushing while spraying an alkaline solution on the surface of a cold-rolled stainless steel plate, removing smudge (dirt) existing on the steel plate surface after cold rolling, and then polishing the pattern, And a stainless steel polished product having a surface property free from pit flaws.

In Patent Document 4, pickling stainless steel with an acidic aqueous solution to expose one or more of conductive metal inclusions and boride metal inclusions on the surface, and then the pH is 7 or more. A neutralization treatment is carried out with a certain alkaline aqueous solution to prevent an increase in the contact electric resistance, and then the substrate is further washed with water and dried.
The pickling is performed by immersing stainless steel in an acidic aqueous solution or by showering the acidic aqueous solution on the stainless steel surface.

  In the above Patent Document 1, a stainless steel plate is immersed in an alkali-based solution. In Patent Document 2, a stainless cold rolled material is immersed in an aqueous solution containing sodium hydroxide and sulfuric acid. If washing is performed by the overflow type immersion method in which immersion is performed while overflowing, the amount of treatment liquid used increases, and the treatment time is also prolonged because the washing is gradually performed in the immersion method. Furthermore, if the amount of oils and fats adhering to the stainless steel material is large, the oils and fats may remain after cleaning, and reliable cleaning may not be performed.

Moreover, in patent document 4, since each solution of an acid and an alkali is used, it is necessary to process a waste liquid separately, and cost increases.
Furthermore, in patent document 3, since brushing is performed while spraying an alkaline solution on a stainless steel plate, a driving source for generating a driving force for brushing is required. If processing can be performed with simple equipment, the cost required for the equipment can be reduced.

  The present invention relates to a method for manufacturing a stainless steel separator for a fuel cell, and shortens the time required for cleaning a stainless steel thin plate used as a separator material and reduces the amount of processing liquid used for cleaning, and the waste liquid processing cost. It is an object to suppress equipment and to simplify the equipment.

  According to the first aspect of the present invention, a step of applying a lubricant to a stainless steel sheet and press-molding the gas flow path and the cooling water flow path, and spraying the cleaning alkaline solution after press-molding on the stainless steel sheet are performed. Removing the lubricant adhering to the stainless steel sheet, removing the alkaline washing solution adhering to the stainless steel sheet by spraying the cleaning water onto the stainless steel sheet, and ion-exchanged water. Spraying the stainless steel sheet to remove the washing water remaining on the stainless steel sheet, and spraying the alkaline solution for passivation to the stainless steel sheet to passivate the stainless steel sheet And passivating the ion-exchanged water attached to the stainless steel sheet by spraying it onto the stainless steel sheet Removing the physical for alkaline solution, and wherein the step of heating and drying the stainless steel sheet, that was formed from.

By spraying the cleaning alkaline solution onto the stainless steel sheet, the lubricant adhering to the stainless steel sheet is forcibly and rapidly removed.
In addition, washing and passivating treatment can be performed quickly by performing washing with washing water and ion exchange water and passivating treatment with an alkaline solution for passivating treatment by spraying.
Furthermore, the waste liquids of the same alkaline cleaning solution and passivating solution are simultaneously processed.
Furthermore, since no brushing or the like is performed, a special drive source is unnecessary.

The invention according to claim 2 is characterized in that the alkaline solution for passivation treatment is a solution having a pH of 9 to 12 and 40 to 60 ° C.
If the stainless steel sheet is passivated with an alkaline solution, metal ions from the stainless steel sheet are not eluted. Further, since the passivation treatment is performed only by spraying with a single solution, the number of treatment steps is reduced.

The invention according to claim 3 is characterized in that the alkaline solution for passivating treatment is a solution to which a pH buffer solution is added.
Since carbon dioxide dissolves in the alkaline solution for passivating treatment by spraying the alkaline solution for passivating treatment, H ⁺ increases in the alkaline solution for passivating treatment to lower the pH. The pH buffer solution suppresses the decrease in pH.

The invention according to claim 4 is characterized in that the heat drying treatment is performed at 100 to 200 ° C.
When the stainless steel thin plate is heated and dried at 100 to 200 ° C., the passive film formed with the alkaline solution for passivating treatment becomes more stable.

The invention according to claim 5 is characterized in that the alkaline solution for cleaning is a solution obtained by adding a surfactant to a basic salt.
If a surfactant is added to the basic salt, bubbles are hardly generated.

  In the invention according to claim 1, since the step of removing the lubricant adhered to the stainless steel sheet by spraying the alkaline solution for cleaning onto the stainless steel sheet is provided, the effect of removing the lubricant is enhanced by spraying. Compared with the conventional removal step by immersion, the removal time can be shortened and the amount of the alkaline cleaning solution required for removal can be reduced.

  Moreover, by performing washing with water and ion-exchanged water and passivating treatment with spray, the time required for these washing and passivating treatment can be further reduced compared to the conventional immersion method, In addition, the amount of washing water and ion exchange water required for washing can be reduced.

Furthermore, since the cleaning solution and the passivation solution are made alkaline, the waste liquids can be treated at the same time, and the cost can be reduced.
Furthermore, since a driving source necessary for conventional brushing or the like is not necessary, the equipment can be simplified and the cost required for the equipment can be reduced.

  In the invention according to claim 2, since the stainless steel thin plate is passivated with the alkaline solution for passivating treatment, there is no elution of metal ions from the stainless steel thin plate, and the passivating treatment with acid is performed. Compared with this, the cost required for waste liquid treatment can be reduced, and the passivation treatment can be performed only by spraying with a single solution, the number of treatment steps is small, and the cost can be further reduced. it can.

  In the invention according to claim 3, by the spray of the alkaline solution for passivating treatment, the pH buffer solution can suppress the decrease in pH due to the carbon dioxide dissolved in the alkaline solution for passivating treatment. Can be formed efficiently and stably.

  In the invention which concerns on Claim 4, the passive film formed with the alkaline solution can be stabilized more by heat drying at 100-200 degreeC, and corrosion resistance can be improved further.

  In the invention which concerns on Claim 5, since the alkaline solution for washing | cleaning was made into the solution which added surfactant to the basic salt, it becomes difficult to generate | occur | produce a bubble and can prevent malfunctions, such as drainage property by a bubble.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
1 (a) to 1 (c) are explanatory views showing a method for producing a stainless steel separator according to the present invention, wherein (a) is a process diagram, and (b) and (c) are separator materials in each process. It is sectional drawing.
In (a), the manufacturing method of a separator is demonstrated in order.
(A) A stainless steel thin plate 10 is press-molded with a press die 11 (specifically, an upper die 12 and a lower die 13) to produce a plurality of press-molding materials 14.

  Press molding is performed to form a groove or the like for supplying fuel gas or oxidant gas to the fuel cell or discharging generated water when the separator made in the final process is incorporated into the fuel cell. .

  (B) The press-molding material 14 is washed. Specifically, when the stainless steel sheet 10 is press-molded, the grease applied to improve the lubrication between the stainless steel sheet 10 and the press die 11 adheres to the press-molding material 14, so that the cleaning liquid (for details) Sprayed on the press-molding material 14 with a spray device 16 to remove (degrease) oil and fat, and then spray water (details will be described later) onto the press-molded material 14 with another spray device. The cleaning liquid adhering to the press molding material 14 is removed (washed with water).

  (C) An alkaline solution for passivation treatment (hereinafter simply referred to as “passivation treatment liquid”) is sprayed on the press molding material 14 by the spray device 18 to passivate the press molding material 14. Form a working film.

At this time, oxygen is dissolved in the passivation treatment liquid by spraying and the amount of dissolved oxygen in the passivation treatment liquid increases, so that hydroxide formation is promoted. For example, when a passive film having a hydroxide of Fe, Cr, Ni and an oxide component is formed, when the separator is incorporated in a fuel cell, the environment around the electrode becomes an acidic atmosphere during power generation of the fuel cell. However, corrosion due to acid can be suppressed, and stable power generation can be maintained over a long period of time.
The mechanism for promoting hydroxide formation is presumed as follows.
The following reaction proceeds in the alkaline solution for passivating treatment.

In the formula (1), the metal M is ionized, and OH ⁻ is generated from oxygen by air bubbling as shown in the formula (2). As a result, OH ⁻ in the alkaline solution for passivating treatment increases, and as shown in the formula (3), generation of hydroxide is promoted from the metal ions and increased OH ⁻ .
Moreover, in the alkaline solution for passivating treatment, the reaction shown below also proceeds by spraying.

As shown in Equation (4), H ⁺ is generated from carbon dioxide and water, and as shown in Equation (5), H ⁺ is also generated from HCO ₃ ⁻ , and H ⁺ increases. The pH of the alkaline solution for activating treatment will be lowered.
However, since, for example, Na ₂ CO ₃ (CO ₃ ²⁻ becomes a conjugate base) is added as a pH buffer solution to the alkaline solution for passivation, the pH of the alkaline solution for passivation is lowered. Can be suppressed.

(D) Since the passivation treatment liquid is adhered to the film forming material 17 formed by forming the passive film, water is sprayed onto the film forming material 17 with another spray device to apply the film forming material 17 to the film forming material 17. Wash with water.
(E) The film forming material 17 is heated and dried in the heat dryer 21. When the film forming material 17 is dried, a separator is formed.

In (b), the press-molding material 14 includes a base material 22 and a conductive material 24 (for example, Cr ₂ B) included in the base material 22 (... indicates a plurality. The same applies hereinafter). The conductive materials 24 are cueed from the surface of the base material 22.

  (C) shows that the passivation film 26 was formed on the surface layer portion of the base material 22 of the film forming material 17 by the passivation process. The conductive material 24 is in a state of protruding from the passive film 26 (that is, in a cueing state).

  FIG. 2 is an explanatory diagram for comparing methods for producing stainless steel separators, in which the examples (this embodiment) and comparative examples were compared from stainless steel material degreasing to heat drying. The embodiment will be described in detail with reference to FIG. The upper row shows examples, and the lower row shows comparative examples. STXX and STXXX in the figure indicate step numbers (the same applies hereinafter).

First, the embodiment will be described step by step.
ST01: Spray degreasing is performed. That is, the alkaline solution for cleaning at 60 ° C. as the above-described cleaning liquid is sprayed on the press-molding material at a pressure of 1 kgf / cm ² for degreasing. The required time at this time is 1 minute, and the amount of liquid used is 10 L (liter) (spray amount per unit time is 10 L / min. The same applies in the following examples).

  The alkaline solution for washing is a detergent (trade name: Pacna) in which a surfactant (polyoxyethylene = alkyl ether C12-15) is added to an alkaline salt (mainly sodium salt) of carbonate, phosphate or carboxylate. -Spray 50-N, manufacturer name: Yuken Industry Co., Ltd.).

  ST02: Spray washing W1 is performed. That is, in order to remove the alkaline washing solution attached to the press-molding material, tap water or industrial water as washing water is sprayed on the press-molding material and washed with water. The required time at this time is 0.25 minutes, and the amount of liquid used is 2.5L.

  ST03: Spray water washing W2 is performed. That is, in order to remove tap water or industrial water adhering to the press-molding material, ion-exchanged water is sprayed on the press-molding material and washed with water. The required time at this time is 0.25 minutes, and the amount of liquid used is 2.5L. The spray water washing W1 and the spray water washing W2 described above are reduced in cost by using tap water or industrial water that is cheaper than ion exchange water, and then using ion exchange water. It is for removing the chlorine component contained in tap water or industrial water. The chlorine component interferes with the passivation reaction.

  ST04 ... A spray passivation process is performed. That is, a passivating treatment is performed by spraying an aqueous NaOH solution (pH 9 to 12, 40 to 60 ° C.) onto the press-molding material as a passivating treatment solution. The required time at this time is 10 minutes.

  ST05 ... Spray water washing W3 is performed. That is, in order to remove the passivation treatment liquid adhering to the film forming material, ion exchange water is sprayed on the film forming material and washed with water. The required time at this time is 0.5 minutes, and the amount of liquid used is 5L.

ST06 ... The film forming material is heated and dried at 100 to 200 ° C. The required time at this time is 10 minutes.
From the above, the total required time from degreasing to heat drying in the example is 22 minutes. Moreover, the sum total of the usage-amount in spray degreasing and spray water washing W1-spray water washing W3 will be 20L.

Next, a comparative example will be described step by step.
ST101 ... ultrasonic degreasing is performed. That is, ultrasonic degreasing of the press-molded material is performed with an alkaline solution for cleaning. The required time at this time is 5 minutes, and the amount of liquid used is 150 L (the immersion method is an overflow method, and the overflow amount per unit time is 30 L / min. The same applies in the following comparative examples).
ST102 ... Immersion degreasing is performed. That is, the press-molding material is immersed in a cleaning alkaline solution and degreased. The required time at this time is 5 minutes, and the amount of liquid used is 150L.

ST103 ... Immersion washing W1 is performed. That is, the press molding material is immersed in tap water and washed with water. The required time at this time is 1 minute, and the amount of liquid used is 30L.
ST104 ... Dipping water washing W2 is performed. That is, the press molding material is immersed in ion exchange water and washed with water. The required time at this time is 1 minute, and the amount of liquid used is 30L.

ST105 ... An immersion passivation treatment is performed. That is, the press-molding material is immersed in an alkaline solution for passivating treatment, and the passivating treatment is performed. The required time at this time is 10 minutes.
ST106 ... Immersion washing W3 is performed. That is, the film forming material is immersed in ion exchange water and washed with water. The required time at this time is 6 minutes, and the amount of liquid used is 180L.
ST107 ... The film forming material is dried by heating. The required time at this time is 10 minutes.

  From the above, the total required time from degreasing to heat drying in the comparative example is 38 minutes. Moreover, the sum total of the usage-amount in degreasing and immersion water washing W1-immersion water washing W3 will be 540L.

  From the above examples and comparative examples, the spray method of the examples was shortened by 16 minutes in required time and 520 L in the amount of liquid used compared with the immersion method of the comparative examples.

3 (a) and 3 (b) are explanatory views showing a first experimental example for confirming the effect of spray cleaning in the method of manufacturing a stainless steel separator according to the present invention, and spraying using an alkaline solution for cleaning. The cleaning power (degreasing power) was compared between cleaning and ultrasonic cleaning / immersion cleaning. (A) is a flow chart of sample preparation and effect confirmation, (b) is a graph for comparison.
In (a), the flow of sample preparation and effect confirmation will be described step by step.
ST11: An etching process is performed to cue the conductive material of a test piece made of stainless steel.

ST12: Apply oil (fat, work oil and rust inhibitor) to the test piece.
The above-mentioned grease is a product name: Cosmo Grease Max No. 1. Composition: lubricating base oil about 91 wt%, thickener (lithium soap) about 7 wt%, lubricating oil additive about 2 wt%, manufacturer name: Cosmo Oil Lubricants Co., Ltd.
Machine oil is a trade name: No. 630 Press working oil, Composition: Petroleum hydrocarbon (mineral oil) approx. 50 wt%, Chlorine extreme pressure additive 10-50 wt%, Sulfur based extreme pressure additive 1-10 wt%, Manufacturer name: Nippon Tooling Oil Co., Ltd. It is.
The rust preventive agent is trade name: Non-raster P30F, composition: rust preventive additive, film-forming agent, solvent, manufacturer name: Yushiro Chemical Industry Co., Ltd.

ST13 ... The test piece is cleaned with the above-described alkaline solution for cleaning.
At this time, when (1) spray cleaning is performed, the solution temperature is 60 ° C., the cleaning time is 1 minute, and the spray pressure is 1 kgf / cm ^2. (2) When performing ultrasonic cleaning and immersion cleaning, ultrasonic cleaning is performed. The solution temperature is 40 ° C., the cleaning time is 5 minutes, the solution temperature in immersion cleaning is 40 ° C., and the cleaning time is 5 minutes.

ST14 ... The test piece is washed with water.
ST15 ... The test piece is dried.
ST16 ... In order to confirm the effect of cleaning, the test piece is immersed in an n-hexane solvent, and the oil and fat remaining on the test piece is dissolved in the n-hexane solvent and extracted.
ST17 ... The n-hexane solvent is spectroscopically analyzed with an infrared spectrometer, and the oil content is measured.

(B) is a graph showing the amount of oil in each test piece obtained in (a), the vertical axis shows the amount of oil remaining on the test piece (unit: mg / cm ² ), and the horizontal axis shows each cleaning method. .
For unwashed oil amount ^{3.5mg / cm 2, 0.55mg / cm} 2 in the case of ultrasonic cleaning, immersion cleaning, 0.15 mg / cm ² next For spray cleaning, spray cleaning, ultrasonic Oil content is 73% less than sonic cleaning and immersion cleaning. That is, spray cleaning has higher cleaning power (degreasing power).

4 (a) and 4 (b) are explanatory views showing a second experimental example for confirming the effect of spray cleaning in the method for producing a stainless steel separator according to the present invention, and spraying using an alkaline solution for cleaning. The cleaning power (degreasing power) according to the cleaning time was compared between cleaning and immersion cleaning. (A) is a flow chart of sample preparation and effect confirmation, (b) is a graph for comparison.
In (a), the flow of sample preparation and effect confirmation will be described step by step.
ST21 ... Cueing of a test piece made of stainless steel material is performed by an etching process.
ST22... Apply fat and oil (same as used in FIG. 3) to the test piece.

ST23 ... The test piece is cleaned (degreased) with the above-described alkaline solution for cleaning.
At this time, (1) in the case of spray cleaning, the solution temperature is 40 ° C. and the spray pressure is 1 kgf / cm ² . (2) In the case of immersion cleaning, the solution temperature is 40 ° C.

ST24 ... The test piece is washed with water.
ST25 ... The test piece is dried.
ST26 ... In order to confirm the effect of washing, the test piece is immersed in an n-hexane solvent, and the oil and fat remaining on the test piece is dissolved in the n-hexane solvent and extracted.

ST27 ... The n-hexane solvent is spectrally analyzed with an infrared spectrometer, and the amount of oil remaining on the test piece is measured.
In the experiment, test pieces spray-washed and immersion-washed test pieces were prepared for each cleaning time, and the oil content of each test piece was measured.
The washing time was 0 (zero) minutes (not washed), 1 minute, 3 minutes, 5 minutes, 10 minutes, 15 minutes and 20 minutes.

(B) is a graph showing the relationship between the amount of oil and the washing time of each test piece obtained in (a), the vertical axis is the amount of oil (unit is mg / cm ² ), and the horizontal axis is the washing time (unit). Represents min).
The spray cleaning, with 1 minute wash time from before washing oil amount 3.5 mg / cm ² to 0.14 mg / cm ² decreases sharply, then became almost flat.

In contrast, in the immersion cleaning, less to 1.0 mg / cm ² oil amount 3.5 mg / cm ² before washing with 1 minute wash time, then oil amount decreases with time, spray washed after 20 (Spray cleaning 0.08 mg / cm ² , immersion cleaning 0.13 mg / cm ² ).

  Thus, in spray cleaning, cleaning time (degreasing time) can be significantly shortened compared to immersion cleaning.

  FIGS. 5 (a) and 5 (b) are explanatory views showing a third experimental example for confirming the effect of spray cleaning in the method for producing a stainless steel separator according to the present invention, and the time of water washing in spray water washing and immersion water washing. The cleaning power was compared. (A) is a flow chart of sample preparation and effect confirmation, (b) is a graph for comparison.

In (a), the flow of sample preparation and effect confirmation will be described step by step.
ST31: A test piece made of stainless steel to which boron is added is prepared.
ST32 ... The test piece is immersed in an alkaline solution for cleaning for 3 minutes.

ST33 ... When spray washing is performed, the amount of water sprayed on the test piece is set to 10 L / min.
ST34 ... When immersion water washing is performed, the amount of water in the overflow method is set to 10 L / min.
ST35: The test piece is immersed in ion exchange water for 60 minutes.
ST36 ... The pH of ion-exchanged water in which the test piece is immersed is measured.

In the experiment, a test piece washed with spray water and a test piece washed with immersion water were prepared for each washing time, and the pH was measured after each test piece was immersed in ion-exchanged water.
The washing time was 15 minutes, 30 minutes, 45 minutes (only spray washing), 60 minutes and 120 minutes.

(B) is a graph showing the relationship between the pH of ion-exchanged water and the washing time, wherein the vertical axis represents pH and the horizontal axis represents the washing time (unit: sec).
In spray rinsing, the pH drops to 7.17 after 15 minutes of rinsing, and the pH is almost flat even when the rinsing time is increased.

In contrast, in immersion water washing, the pH only decreased to 7.70 after 15 minutes of water washing, and then gradually decreased as the water washing time increased. I didn't go down.
Thus, in spray water washing, pH can be lowered in a short time compared with immersion water washing, that is, water washing in a short time becomes possible.

FIG. 6 is a graph (corrosion experiment) showing a fourth experimental example for confirming the effect of the passivation treatment by spraying in the method for producing a stainless steel separator according to the present invention. Corrosion current densities of test pieces (finally subjected to heat drying) in which a passive film was formed at each treatment time in the activation treatment were measured and compared. Three test pieces were prepared for each treatment condition, the corrosion current density was measured, and the average of the three pieces was plotted on a graph. If the corrosion current density is small, it means that corrosion is difficult. The vertical axis of the graph represents the corrosion current density (unit: μA / cm ² ), and the horizontal axis represents the processing time of passivation treatment (unit: min). Moreover, a broken line is a requirement value (5.1 microampere / cm < ² >) of a corrosion current density.

The corrosion test conditions are shown below.
Corrosion experiment conditions Test solution: sulfuric acid aqueous solution (pH 3, concentration 0.005%, temperature 90 ° C.)
Test piece potential: 638.8 mV constant (set based on saturated gypsum electrode (SCE))
Hereinafter, it is described as “638.8 mV vs. SCE”.
Test method: Corrosion current density measured after holding the above test specimen potential for 30 minutes

The passivating conditions are shown below.
Spray method Treatment liquid: NaOH aqueous solution (pH 10.7-11, temperature 60 ° C.)
Spray amount: 100 L / min Spray time: 10 minutes Heat drying: 110 ° C., 10 minutes

・ Immersion method Treatment liquid: NaOH aqueous solution (pH 10.8, temperature 50 ° C.)
Immersion time: 10 minutes Heat drying: 110 ° C., 10 minutes

  Corrosion current density was equivalent between the spray method and the immersion method for each treatment time. That is, both the spray method and the dipping method had a requirement value of 3 minutes or more, and the treatment time was not different between the spray method and the dipping method.

FIG. 7 is a graph showing a fifth experimental example for confirming the effect of passivation treatment by spraying in the method for producing a stainless steel separator according to the present invention, which was produced by a separator produced by a spray method and an immersion method. The penetration resistance (contact resistance) by a separator is measured and compared. The vertical axis of the graph represents penetration resistance (unit: mΩ · cm ² ), and the horizontal axis represents two conditions when measuring penetration resistance.

  The conditions for measuring the penetration resistance are one in which two separators are brought into contact with each other and the penetration resistance between the separators is measured, and the other is carbon paper that serves as an electrode between the two separators. The penetration resistance between the separators (herein described as between the separator and the electrode) is measured by sandwiching one sheet. The surface pressure between the separators at the time of penetrating resistance measurement is that when the penetrating resistance is stabilized when the surface pressure is gradually increased.

The passivating conditions are shown below.
Spray method Treatment liquid: NaOH aqueous solution (pH 10.7-11, temperature 60 ° C.)
Spray amount: 100 L / min Spray time: 10 minutes Heat drying: 110 ° C., 10 minutes

・ Immersion method Treatment liquid: NaOH aqueous solution (pH 10.8, temperature 50 ° C.)
Immersion time: 10 minutes Heat drying: 110 ° C., 10 minutes

The penetration resistance between the separators and the penetration resistance between the separators and the electrodes were equal between the spray method and the immersion method, respectively, and the penetration resistance between the separators and the electrodes was less than the target value of 20.5 mΩ · cm ² .

  As described above with reference to FIG. 1 and FIG. 2, the present invention first includes a step of press-molding the gas flow path and the cooling water flow path by applying oil and fat as a lubricant to the stainless steel thin plate 10, and cleaning. The step of removing the oils and fats adhering to the press molding material 14 by spraying the press molding material 14 after the alkaline solution for press molding is sprayed, and the press molding material 14 by spraying tap water or industrial water onto the press molding material 14 A step of removing the alkaline washing solution adhering to 14, a step of removing tap water or industrial water remaining in the press molding material 14 by spraying ion-exchanged water on the press molding material 14, and a press molding material 14 A step of spraying an alkaline solution for passivating treatment onto the press-molding material 14 to passivate, and ion-exchanged water to passivate film It comprises the step of removing the alkaline solution for passivating treatment adhering to the passive film forming material 17 by spraying the material 17 and the step of heating and drying the passive film forming material 17. .

  By providing the step of removing the oil and fat adhering to the press-molding material 14 by spraying the alkaline solution for cleaning onto the press-molding material 14, the effect of removing the oil and fat can be enhanced by spraying, and the conventional dipping removal process can be performed. In comparison, the removal time can be shortened and the amount of the alkaline solution for cleaning required for the removal can be reduced.

  In addition, by washing with washing water (tap water or industrial water) and ion-exchanged water and passivating treatment, the time required for these washing and passivating treatment can be compared with the conventional dipping method. It can be further shortened, and the amount of tap water, industrial water or ion exchange water required for cleaning can be reduced.

Furthermore, since the cleaning solution and the passivation solution are made alkaline, the waste liquids can be treated at the same time, and the cost can be reduced.
Furthermore, since a driving source necessary for conventional brushing or the like is not necessary, the equipment can be simplified and the cost required for the equipment can be reduced.

Furthermore, by spraying the alkaline solution for passivating treatment, the amount of dissolved oxygen in the alkaline solution increases, OH ⁻ increases, and the increased OH ⁻ and metal ions are combined to form hydroxide. Can be promoted. Therefore, a passive film having a hydroxide can be formed on the press-molding material 14, and when the separator is incorporated in a fuel cell, corrosion of the separator in an acidic atmosphere during power generation can be suppressed.

Second, the present invention is characterized in that the passivating alkaline solution is a solution having a pH of 9 to 12 and 40 to 60 ° C.
By passivating the press-molding material 14 with an alkaline solution for passivating treatment, metal ions are not eluted from the press-molding material 14 and are required for waste liquid treatment as compared with the passivating treatment with acid. The cost can be reduced, and the passivation treatment can be performed only by spraying with a single solution, the number of treatment steps is small, and the cost can be further reduced.

Thirdly, the present invention is characterized in that the passivating alkaline solution is a solution to which a pH buffer solution is added.
By spraying the alkaline solution for passivating treatment, the pH buffer can suppress the decrease in pH due to carbon dioxide dissolved in the alkaline solution for passivating treatment, and a passive film can be formed efficiently and stably. can do.

Fourthly, the present invention is characterized in that the heat drying treatment is performed at 100 to 200 ° C.
By heat drying at 100 to 200 ° C., the passive film formed with the alkaline solution can be further stabilized, and the corrosion resistance can be further improved.

Fifth, the present invention is characterized in that the alkaline cleaning solution is a solution obtained by adding a surfactant to a basic salt.
By making the alkaline solution for washing into a solution in which a surfactant is added to a basic salt, bubbles are less likely to be generated, and problems such as drainage due to bubbles can be prevented.

  In the present invention, hydroxide formation was promoted by showering the alkaline solution for passivation treatment, but in addition to showering the alkaline solution for passivation treatment, the alkaline solution for passivation treatment was stored. Hydroxide formation may be further promoted by blowing air into the tank (that is, an air valve ring).

  The method for producing a stainless steel separator of the present invention is suitable for a fuel cell.

Explanatory drawing which shows the manufacturing method of the stainless steel separator which concerns on this invention Explanatory drawing comparing the manufacturing method of stainless steel separator Explanatory drawing which shows the 1st experiment example which confirms the effect of the spray washing in the manufacturing method of the stainless steel separator which concerns on this invention Explanatory drawing which shows the 2nd experiment example which confirms the effect of the spray washing in the manufacturing method of the stainless steel separator which concerns on this invention Explanatory drawing which shows the 3rd experiment example which confirms the effect of the spray washing in the manufacturing method of the stainless steel separator which concerns on this invention The graph which shows the 4th experiment example which confirms the effect of the passivation process by the spray in the manufacturing method of the stainless steel separator which concerns on this invention. The graph which shows the 5th experiment example which confirms the effect of the passivation process by the spray in the manufacturing method of the stainless steel separator which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Stainless steel thin plate, 14 ... Press molding raw material, 16, 18 ... Spray apparatus, 17 ... Film-forming material, 21 ... Heating dryer.

Claims (5)

Applying a lubricant to a stainless steel sheet and press-molding the gas flow path and the cooling water flow path;
Removing the lubricant adhering to the stainless steel sheet by spraying the stainless steel sheet after press molding the alkaline solution for washing;
Removing the washing alkaline solution adhering to the stainless steel sheet by spraying washing water onto the stainless steel sheet;
Removing the washing water remaining on the stainless steel sheet by spraying ion exchange water on the stainless steel sheet;
Spraying the stainless steel sheet with a passivating alkaline solution to passivate the stainless steel sheet;
Removing the alkaline solution for passivating treatment adhering to the stainless steel sheet by spraying ion exchange water on the stainless steel sheet;
Heating and drying the stainless steel sheet;
A method for producing a stainless steel separator for a fuel cell, comprising:   The method for producing a stainless steel separator for a fuel cell according to claim 1, wherein the alkaline solution for passivating treatment is a solution having a pH of 9 to 12 and a temperature of 40 to 60 ° C.   The method for producing a stainless steel separator for a fuel cell according to claim 2, wherein the alkaline solution for passivating treatment is a solution to which a pH buffer solution is added.   The method for producing a stainless steel separator for a fuel cell according to claim 1, wherein the heat drying treatment is performed at 100 to 200 ° C. 5.   The method for producing a stainless steel separator for a fuel cell according to any one of claims 1 to 4, wherein the washing alkaline solution is a solution obtained by adding a surfactant to a basic salt.

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