KR100885041B1 - Stainless separator for fuel cell having coating layer selected from mnx, m/mnx, mcy, mbz and method for the same - Google Patents

Abstract

A stainless separator for a fuel cell is provided to maintain corrosion resistance and electric conductance for a long time and reduce manufacturing cost of the stainless separator. A method for manufacturing a stainless separator for a fuel cell comprises the following steps. The stainless material(200) is prepared. A Cr-rich passivation layer(210) is coated on a surface of the stainless material. A selected transition metal coating layer(220) is formed on the surface of the stainless material. The Cr-rich passivation layer includes more chrome(Cr) and less the iron(Fe) than the surface of the stainless material. The transition metal coating layer is selected from a metal-nitride layer, a metal carbide layer, and a metal boride layer.

Description

Stainless separator for fuel cell having a coating layer selected from metal nitride layers (MNx), metal carbide layers (MCy), and metal boride layers (MBz), and a method of manufacturing the same , M / MNx, MCy, MBz and method for the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel separator plate for fuel cells and a method of manufacturing the same. More particularly, the present invention relates to a metal nitride on a surface of a polymer electrolyte fuel cell (PEMFC) plate having excellent corrosion resistance, conductivity, and durability. The present invention relates to a stainless steel separator for a polymer electrolyte fuel cell having a coating layer selected from a layer (MN _x ), a metal carbide layer (MC _y ), and a metal boride layer (MB _z ).

Since the unit cell of the fuel cell is low in practicality due to low voltage, generally several to hundreds of unit cells are stacked and used. In the stacking of the unit cells, the electrical connection between the unit cells is made, and the separating plate serves to separate the reaction gas.

The bipolar plate, together with the membrane electrode assembly (MEA), is a key part of the fuel cell. The structural support of the membrane electrode assembly and the gas diffusion layer (GDL), the collection and transfer of generated currents, the transport and removal of the reaction gas, and the heat of reaction It plays various roles such as transporting cooling water for removal.

Accordingly, the material properties of the separator include excellent electrical conductivity, thermal conductivity, gas sealing property, and chemical stability.

As a material of such a separating plate, it has been manufactured using a graphite-based material and a composite graphite material in which resin and graphite are mixed.

However, graphite-based separators exhibit low strength and hermeticity compared to metal-based materials. In particular, studies on metal-based separators have been actively conducted in recent years due to high process cost and low mass productivity.

When the metal is applied as the material of the separator, it is possible to reduce the volume and weight of the fuel cell stack by reducing the thickness of the separator and to manufacture by stamping, thereby securing mass productivity.

However, metal corrosion caused by fuel cell use may cause contamination of the membrane electrode assembly, thereby degrading fuel cell stack performance, and thick oxide film growth on the metal surface may increase fuel cell internal resistance after prolonged use. It can act as a factor.

As metal materials for fuel cell separators, stainless steel, titanium alloys, aluminum alloys and nickel alloys are considered as candidate materials. Double stainless steel has attracted much attention as a separator material due to relatively low material cost and excellent corrosion resistance, but still does not show satisfactory levels in terms of corrosion resistance and electrical conductivity.

The problem to be solved by the present invention is a stainless steel separator plate for fuel cells and corrosion resistance and contact resistance satisfying the DOE (US energy) standards even after prolonged exposure to the operating environment of the high-temperature and high-humidity fuel cell and its manufacturing method. In providing.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The method of manufacturing a stainless steel separator plate for fuel cells includes the steps of: (a) preparing a stainless steel base plate; (b) a surface modification step of reducing the iron (Fe) component of the stainless steel base material surface layer to form a Cr-rich passivation film having an increased relative amount of chromium (Cr) component on the surface of the stainless steel sheet; And (c) forming a coating layer selected from a metal nitride layer (MN _x ), a metal carbide layer (MC _y ), and a metal boride layer (MB _z ) on the surface of the surface-modified stainless steel base material.

Stainless steel separator plate for a fuel cell according to the present invention for solving the technical problem is a stainless steel sheet base material; Cr-rich passivation film having a chromium (Cr) component of 20 ~ 75wt% formed on the surface of the stainless steel base material; And a coating layer selected from a metal nitride layer (MN _x ), a metal carbide layer (MC _y ), and a metal boride layer (MB _z ) formed on the passivation film at a thickness of 30 to 300 nm.

According to the stainless steel separator plate for fuel cells manufactured according to the present invention, corrosion resistance and electrical conductivity are excellent even when used for a long time in a fuel cell operating environment as well as in the early stage.

In addition, the method for manufacturing a stainless steel separator plate for fuel cells according to the present invention enables surface treatment to obtain excellent properties even when using a conventional stainless steel base plate having a low cost, thereby lowering the manufacturing cost of the stainless separator plate.

The stainless steel separator plate for fuel cells manufactured by the present invention may have a corrosion current of 1 μA / cm 2 or less and a contact resistance value of 20 mΩ · cm 2 or less on both sides.

Specific details of other embodiments are included in the detailed description and the accompanying drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

In addition, in the drawings, the size and thickness of layers and films or regions are exaggerated for clarity of description, and when any film or layer is described as being formed "on" of another film or layer, It may be directly on top of the other film or layer, and a third other film or layer may be interposed therebetween.

1 is a process flow chart illustrating a method for manufacturing a stainless steel separator plate for fuel cells according to the present invention, and FIGS. 2 to 5 show process perspective views in the respective process steps of FIG. 1.

In order to manufacture the stainless steel separator plate for the fuel cell of the present invention, first, a stainless steel sheet 200 is provided as shown in FIG. 2 (S110).

As the stainless steel sheet 200 used in this process step, a stainless steel sheet containing 16 to 28 wt% of chromium component, which is generally commercially available, is used, and even if a stainless steel sheet containing about 18 wt% of chromium component is used. It's okay.

Specifically, the base material of the stainless steel sheet 200 is 0.08 wt% or less of carbon (C), 16 to 28 wt% of chromium (Cr), 0.1 to 20 wt% of nickel (Ni), and 0.1 to 6 wt% of molybdenum ( Mo), 0.1 to 5 wt% tungsten (W), 0.1 to 2 wt% tin (Sn), 0.1 to 2 wt% copper and other residual amounts of stainless steel sheet containing iron (Fe), characterized in that More specifically, austenite-based stainless steel, such as SUS 316L and 0.2t, is used.

This step may include a cleaning process for removing impurities on the surface of the stainless steel sheet 200 using acidic and alkaline degreasing agents prior to surface modification and coating layer formation to be performed later.

Next, as shown in FIG. 3, the surface of the stainless steel sheet 200 is modified (S120).

The stainless steel sheet 200 includes a chromium component and a nickel component having high corrosion resistance, but most of the content is made of iron (Fe).

As a result, the stainless steel sheet 200 is combined with oxygen in the air in a natural state to form an oxide film on the surface. Since the oxide film is a non-conductor, the stainless steel sheet 200 may act as a factor of lowering the electrical conductivity of the entire stainless steel sheet.

Therefore, it is necessary to modify the surface properties of the stainless steel sheet 200 which is inferior in corrosion resistance.

That is, only the iron component (Fe) present in the surface layer of the stainless steel sheet 200 is selectively etched through surface modification.

After the surface modification process as described above, the surface of the stainless steel sheet 200 is changed to a Cr-rich passive film (210), the content ratio of the chromium component in the metal components of the Cr-rich passive film (210) Is about 20 ~ 75wt%, contains less than 30wt% of iron, and the ratio of (Cr + Ni) / Fe is 1 or more when it is expressed as the main component ratio of Cr-rich passive film (210). It becomes a state.

The reason why selective metal dissolution is possible is that iron oxide is easily dissolved in acid in the surface oxide layer, whereas chromium oxide is more stable than iron oxide and is not easily dissolved.

Solutions and conditions used for surface modification are as follows.

The surface modification solution contains 5-20 wt% of pure nitric acid (HNO ₃ ), 2-15 wt% of pure sulfuric acid (H ₂ SO ₄ ), and water in the remaining amount, and the temperature of 50 ° C. to 80 ° C. is appropriate for the deposition time. Silver is 30 seconds to 30 minutes or less, but considering the productivity according to the treatment time to 30 seconds to 10 minutes or less, it is preferable to adjust the concentration of nitric acid and sulfuric acid.

In the surface modification solution according to the present invention, any one or both selected from oxalic acid and hydrogen peroxide (H ₂ O ₂ ) is added to the first surface modification solution (nitric acid + sulfuric acid) to accelerate the surface metal dissolution rate of the stainless steel sheet. You can also

In addition, in the surface modification, by depositing the surface modification solution containing sulfuric acid (H ₂ SO ₄ ) using an electrochemical method and applying a SHE potential of more than 0 ~ 1.0V, iron component (Fe Selective dissolution in) becomes possible.

When the surface modification process is performed, the chromium component (Cr) is hardly dissolved, and a large amount of iron (Fe) and some nickel (Ni) components are selectively dissolved to form iron (Fe) in the surface layer of the stainless steel sheet 200. In addition, the chromium (Cr) and nickel (Ni) components are concentrated in the surface layer.

As a result of the surface modification, the thickness of the Cr-rich passive film 210 is 5 to 100 nm.

Next, as shown in FIG. 4, a coating layer is formed on the Cr-rich passive film 210 (S130).

In this case, the coating layer 220 is selected from the metal nitride layer (MN _x ), the metal carbide layer (MC _y ), the metal boride layer (MB _z ) and the reason for forming the coating layer 220 is as follows.

If the surface of the stainless steel sheet 200 is modified, as described above, the passivation film 210 in which the chromium (Cr) component is concentrated may be formed, thereby ensuring excellent corrosion resistance and conductivity at an initial stage.

However, when the surface-modified stainless steel separator is exposed for a long time in the operating environment of a high-humidity fuel cell, the thickness of the passivation film is gradually thickened. Since the passivation film is composed mostly of metal oxide, Corrosion resistance is maintained over operating time, but electrical conductivity becomes worse.

Therefore, the metal nitride layer (MN _x ) and the metal carbide layer (MC _y ) which are excellent in corrosion resistance and conductivity at the same time on the Cr-rich passivation film 210 and which can suppress the growth of the passivation film even during long time operation. ), By forming a coating layer 220 selected from the metal boride layer (MB _z ) it is possible to manufacture a fuel cell separator having excellent corrosion resistance and conductivity even during the initial as well as long-term use.

In this case, the metal (M) constituting the coating layer 220 selected from the metal nitride layer (MN _x ), the metal carbide layer (MC _y ), and the metal boride layer (MB _z ) has electrical conductivity and corrosion resistance when forming nitride. At the same time, it can be selected from excellent transition metals, specifically, it is preferable to use chromium (Cr), titanium (Ti), zirconium (Zr), tungsten (W), where x is 0.5 ≦ x ≤ 1, y is 0.42 ≤ y ≤ 1, z is 0.5 ≤ z ≤ 2.

The thickness of the coating layer 220 is preferably formed to a thickness of 30 ~ 300nm, preferably 30 ~ 100nm, the reason is that the effect is insignificant when less than 30nm, the high metal target price and long time if more than 300nm This is because the production efficiency decreases due to the process of.

The coating layer 220 selected from the metal nitride layer (MN _x ), the metal / metal nitride layer (M / MN _x ), the metal carbide layer (MC _y ), and the metal boride layer (MB _z ) is formed by sputtering and sputtering. The same physical vapor deposition method or arc ion plating method may be used, but is not limited thereto.

In the present invention, active sputtering is relatively easy to control in order to form a coating layer 220 selected from a metal nitride layer (MN _x ), a metal carbide layer (MC _y ), and a metal boride layer (MB _z ). It will be described with respect to the formation of the coating layer 220 by using a sputtering method.

Examples of the metal material constituting the coating layer 220 selected from the metal nitride layer (MN _x ), the metal carbide layer (MC _y ), and the metal boride layer (MB _z ) include chromium (Cr), titanium (Ti), and zirconia ( Zr) and tungsten (W) were used.

However, techniques other than sputtering may be used.

In order to form the coating layer 220, it is preferable to use a metal having a purity of at least nine nines (99.99) as a sputtering target.

The method of forming the coating layer using the sputtering method will be described in more detail. The stainless steel sheet 200 and the metal target are loaded into the sputtering chamber, and the sputtering process is performed in an argon + nitrogen (Ar + N ₂ ) gas atmosphere. The coating layer 220 is formed on the passivation film 210.

However, in this case, in order to form a coating layer consisting of two layers, only an argon gas (Ar) gas is used to form an atmosphere gas and a metal layer (M). When argon + nitrogen (Ar + N ₂ ) gas is continuously supplied, two It is possible to form a layered coating layer continuously.

That is, in the above process, when the metal layer M is formed, the inside of the sputtering chamber is processed in an argon gas (Ar) atmosphere, and when the metal nitride layer (MNx) is formed, the inside of the sputtering chamber is formed of argon gas and nitrogen gas ( The process is advanced to the atmosphere in which N ₂ ) coexists.

Specifically, referring to FIG. 4, the coating layer 220 is formed on the passivation film 210 in the form of a continuous film.

<Examples and Comparative Examples>

Hereinafter, specific examples and comparative examples will be described that the separator manufactured by the method for manufacturing a stainless steel separator plate for fuel cells according to the embodiments of the present invention has excellent corrosion current and contact resistance properties. Details not described herein are omitted because they can be sufficiently inferred by those skilled in the art.

Table 1, Table 2 and Table 3 show the surface modification conditions (temperature, time, current density, solution composition) and coating layer formation conditions (coating layer type, design) by using 316L as the base plate of stainless steel sheet by immersion method and electrochemical method. , To show the results of measuring the corrosion current and the contact resistance for the stainless steel separator according to Examples 1 to 18 and Comparative Examples of the present invention manufactured with different thickness).

Specifically, in the case of Examples 1 to 7 and Example 10, the surface modification and chromium nitride layer (CrN or Cr ₂ N) was formed at the same time (Example 4, Example 6 were Cr / CrN multilayer ( multi-layers), Examples 8 to 9 and Examples 11 to 18 include titanium nitride, carbides and borides (TiN, TiC or TiB ₂ ), zirconium nitrides, carbides or borides (ZrN , ZrC and ZrB ₂ ), chromium carbide and boride (Cr ₃ C ₂ , Cr ₇ C ₃ or CrB ₂ ) and tungsten carbide (WC) were formed, and in the case of Comparative Example 1 the coating layer ( In the case of forming a chromium nitride (CrN) having a thickness of 15 nm outside the thickness range of 220), in the case of Comparative Example 2 only the surface modification and the coating layer is not formed, in the case of Comparative Example 3 chromium nitride without surface modification Only the layer (CrN) was formed.

1. Measurement of contact resistance

5 is a view showing a contact resistance measuring device for measuring the contact resistance of the stainless steel sheet according to the present invention.

Referring to Figure 5, the contact between the stainless steel (SS) and carbon paper modified David method (Davies method) in order to obtain an optimized constant for fastening the cell for measuring the contact resistance of the stainless steel sheet 500 Used to measure resistance.

Contact resistance was measured with Zahner's IM6 instrument using the four-wire current-voltage measurement principle.

In the constant current mode, the contact resistances were measured in the range of 10 kHz to 10 mHz with DC 2A and AC 0.2A.

Carbon paper used 10BB of SGL Corporation.

The contact resistance measuring device 50 is provided with a carbon paper 520, a gold plated copper plate 510 up and down with the specimen 500 interposed therebetween, and the copper plate 510 is a current supply device ( 530 and the voltage measuring device 540.

The voltage was measured by applying a current of DC 2A / AC 0.2A to a current supply device 530 (IM6 of Zahner) capable of supplying current to the specimen 500.

An instron capable of providing pressure so that the specimen 500, the carbon paper 520, and the copper plate 510 has a laminated structure above and below the copper plate 510 of the contact resistance measuring device 50. (Model 5566, compression test) is prepared. The pressure gauge provides a pressure of 50 to 150 N / cm ² to the contact resistance measuring device 50.

The contact resistance of the specimen 500 of the Examples and Comparative Examples shown in Tables 1 and 2, that is, the stainless steel sheet, was measured by the contact resistance measuring apparatus 50 prepared as described above.

2. Measurement of corrosion current

EG & G 273A was used as a measuring instrument for measuring the corrosion current of the stainless steel separator of the present invention. Corrosion endurance test was carried out under simulated environment of PEFC (Polymer Electrolyte Fuel Cell).

As a test solution for corrosion of the stainless steel sheet according to the present invention using 0.1NH ₂ SO ₄ + 2ppm HF solution at 80 ℃, O ₂ bubbling for 1 hour after OCP (Open Circuit Potential)-0.25V ~ 1V vs SCE range Measured at

In addition, physical properties were measured at -0.24V vs SCE for PEFC anode environment and 0.6V vs SCE for Saturated Calomel Electrode (SCE).

Here, the physical property comparison was evaluated through the corrosion current data of 0.6 V vs SCE in the cathode environment similar to the fuel cell environment.

The anode environment is an environment in which hydrogen is separated into hydrogen ions and electrons in a membrane electrode assembly (MEA), and the cathode environment is a reaction in which oxygen combines with hydrogen ions and electrons to generate water. It's an environment that happens.

In this case, since the potential of the cathode environment is high and the harsher corrosion conditions are more severe, it is preferable to test the corrosion resistance based on the cathode environment.

For the application of the polymer electrolyte fuel cell, the corrosion current density of the stainless steel sheet is preferably ¹ μA / cm ² or less.

3. Analysis of Corrosion Current and Contact Resistance Measurement Results

Referring to Table 1, Table 2, and Table 3, when the surface modification-coating layer was formed as in the embodiments of the present invention, it can be seen that the corrosion current has a value between 0.5 to 1.0 mA / cm 2, and the contact In the case of resistance, it turns out that the value of 13-18 mPa * cm <2> is shown.

In the case of forming a chromium nitride layer having a thickness of 15 nm after surface modification as in Comparative Example 1, the contact resistance value was 17.4 mΩ · cm 2, and the corrosion current value was 0.94 ㎂ / ㎠, When the resistance value is 17.5 mΩ · ㎠ and the corrosion current value is 0.95 ㎂ / ㎠, and the chromium nitride layer is formed without the surface modification process as in Comparative Example 3, the contact resistance value is 35 mΩ · ㎠ and the corrosion current value is 2.3 ㎂ / It turns out that the value of cm <2> is shown.

Although the contact resistance and the corrosion current value of the above embodiments and the comparative examples are all satisfying the DOE standard, this is because the initial value before the fuel cell is operated for a long time, and will be described below. In the long-term durability evaluation of the fuel cell, it can be seen that the difference between the values of the embodiments and the comparative examples is more remarkable.

4. Evaluation and results of fuel cell simulation environment corrosion resistance and contact resistance

(1) Evaluation of simulated environment corrosion resistance and contact resistance

The fuel cell environmental simulation of the stainless steel separator of the present invention used EG & G 273A. The specimen was charged in a 0.1NH ₂ SO ₄ + 2ppm HF solution at 80 ° C., followed by O ₂ bubbling for 1 hour, and a constant voltage of 0.6 V vs SCE was applied to the specimen. After applying a constant voltage for a certain time, the corrosion resistance and contact resistance of the specimen were measured. By repeating the above work, the corrosion resistance and contact resistance changes in the fuel cell simulation environment were evaluated for a long time.

(2) Evaluation result of simulated environment corrosion resistance and contact resistance

6 is a graph showing the results of the fuel cell simulation environment corrosion resistance measured by the above method.

Referring to FIG. 6, it can be seen that in Example 1 and Comparative Example 2, the corrosion current value is maintained almost constant at 1 mA / cm 2 or less even after the initial and 1,000 hours have elapsed. In addition, it can be seen that the initial corrosion current value also exceeds 1 kW / cm 2, which is considered to be due to the exfoliation of the CrN layer in Comparative Example 3.

FIG. 7 shows the results of the contact resistance evaluation after 2,000 hours exposure of the specimens of Examples 1, 4 and 8 to 18, and Comparative Examples 1 and 2 in the fuel cell simulation environment measured by the above method. This graph is shown.

Referring to FIG. 7, in the case of Examples 1, 4, and 8 to 18, 2,000 hours were obtained in the case of Comparative Example 1 and Comparative Example 2, while the values below the DOE standard were maintained even after 2,000 hours had elapsed. After that, it can be seen that the contact resistance value exceeding the DOE standard is shown.

The reason for the above results was obtained in the case of Comparative Example 1 because the CrN layer was peeled off or the passivation film was grown to a thickness higher than CrN. In Comparative Example 2, the passivation film was continuously grown, whereas in the case of the Example, the metal compound layer formed on the surface performed well as a corrosion resistant and conductive coating layer that suppressed the growth of the passivation film thereunder. It seems to be.

5. Long-term durability evaluation and results of fuel cell

(1) long-term durability evaluation method

A separator having a serpentine flow path was used to supply the reactant gas, and a membrane-electrode assembly (Gore's model name 5710) and a gas diffusion layer (SGL's model 10BA) were placed between the separator plates and fastened to a constant pressure. The cell was fabricated.

The fuel cell performance was evaluated using the unit cell. The fuel cell operating device used NSE Test Station 700W class and the electronic load device for fuel cell performance evaluation using KIKUSUI E-Load, 0.01A / cm ² Current 15 A current 15 second cycle was continuously applied at s- ^{1 A} / cm ² .

Hydrogen and air were used as the reaction gas, and the flow rate was supplied after humidifying 100% of relative humidity while maintaining a constant stoichiometric ratio of hydrogen 1.5 and air 2.0 according to the current. Humidifier and cell temperature was kept constant at 65 ℃ and the performance was evaluated under atmospheric pressure conditions. At this time, the active area (active area) was 25 cm 2, the operating pressure was 1 atm.

(2) Long-term durability evaluation result

8 is a graph showing the evaluation results after the elapse of 2,000 hours for the specimens of Examples 1, 4 and 8 to 18, and Comparative Examples 1 and 2 according to the long-term durability evaluation method.

Referring to FIG. 8, in all cases, the generated voltage was initially 0.62V or more, but in the case of Comparative Example 1, the generated voltage was reduced to about 0.58V after 2,000 hours. In Comparative Example 2, the generated voltage was 0.57V after the 2,000 hours. Falls to V.

In contrast, fuel cells using stainless steel separators manufactured according to Examples 1, 4, and 8 to 18 of the present invention have excellent durability and have a small amount of less than 0.02V compared to the initial stage even after 2,000 hours. It can be seen that a decrease in the generated voltage is indicated.

1 is a process flow diagram illustrating a method of manufacturing a stainless steel separator plate for fuel cells according to the present invention.

2 to 4 show a process perspective view in each process step of FIG.

5 is a view showing a contact resistance measuring device for measuring the contact resistance of the stainless steel sheet according to the present invention.

6 is a graph showing the results of the fuel cell simulation environment corrosion resistance evaluation for the specimens of Example 1, Comparative Example 2 and Comparative Example 3.

7 is a graph showing the results of fuel cell simulated environmental contact resistance evaluation for the specimens of Examples 1, 4, 8 and 18 and Comparative Examples 1 and 2. FIG.

8 is a graph showing the results of evaluation of the specimens of Examples 1, 4, 8 and 18 and Comparative Example 1 according to the long-term durability evaluation method described above.

Claims (17)

(a) preparing a stainless steel sheet base material; (b) a surface modification step of forming a Cr-rich passivation film in which a relative amount of chromium (Cr) component is increased on the surface of the stainless steel sheet by reducing the iron (Fe) component of the stainless steel base material surface layer; And (c) a metal nitride layer (MN _x ), a metal carbide layer (MC _y ), and a metal boride layer (MB _z ) containing a metal (M) selected from transition metals on the surface of the stainless steel base material surface-modified; Method of manufacturing a metal separator plate for a fuel cell comprising the step of forming a coating layer is selected. (Where x is 0.5 ≦ x ≦ 1, y is 0.42 ≦ y ≦ 1, and z is 0.5 ≦ z ≦ 2) The method of claim 1, In the step (c), the applied metal is metal (M) is one or two or more selected from chromium (Cr), titanium (Ti), zirconium (Zr), tungsten (W). Method for producing stainless steel separator. delete The method of claim 1, The passivation film constituting the surface layer of the stainless steel sheet after the step (b) has a ratio of (Cr + Ni) / Fe in an atomic ratio of 1 or more. The method of claim 1, The coating layer is a manufacturing method of a stainless steel separator plate for a fuel cell, characterized in that formed in the form of a film (film) having a thickness of 30 ~ 300nm. The method of claim 1, The surface modification process of step (b) is carried out by depositing a solution containing sulfuric acid (H ₂ SO ₄ ) and nitric acid (HNO ₃ ) or by spraying the solution on the surface of the stainless steel base material Method for producing a stainless steel separator plate for batteries. The method of claim 1, The surface modification process of step (b) is carried out by immersing in a surface modification solution containing sulfuric acid (H ₂ SO ₄ ) and applying a potential (or current) in the SHE region of more than 0 ~ 1.0V The manufacturing method of the stainless steel separator plate for fuel cells. The method of claim 6, The surface reforming solution further comprises at least one additive selected from hydrogen peroxide (H ₂ O ₂ ) and oxalic acid (C ₂ H ₂ O ₄ ; oxalic acid). The method of claim 1, In the step (c), the coating layer is a method of manufacturing a stainless steel separator plate for fuel cells, characterized in that formed by sputtering or arc ion plating. The method of claim 9, The sputtering method is a method of manufacturing a stainless steel separator plate for fuel cells, characterized in that the active sputtering (reactive sputtering) specifically. The method of claim 1, The stainless steel base plate has a chromium component of 16 ~ 28wt% method for producing a stainless steel separator plate for fuel cells. Stainless steel plate base material; Cr-rich passivation film having a chromium (Cr) component of 20 ~ 75wt% formed on the surface of the stainless steel base material; And A thickness of 30 ~ 300nm formed on the passivation film, a stainless steel separator for a fuel cell comprising a coating layer selected from metal nitride layer (MN _x ), metal carbide (MC _y ), metal boride (MB _z ). (Where x is 0.5 ≦ x ≦ 1, y is 0.42 ≦ y ≦ 1, and z is 0.5 ≦ z ≦ 2) The method of claim 12, The coating layer is a stainless steel separator plate for fuel cells, characterized in that formed in a continuous (film) form on the passivation film. The method of claim 12, Metal (M) applied to the coating layer is a stainless steel separator plate for fuel cells, characterized in that selected from chromium (Cr), titanium (Ti), zirconium (Zr), tungsten (W). The method of claim 12, The passivation film is a stainless steel separator plate for fuel cells, characterized in that the ratio of (Cr + Ni) / Fe in atomic ratio. The method of claim 12, The stainless steel base material is 0.08 wt% or less carbon (C), 16 to 28 wt% chromium (Cr), 0.1 to 20 wt% nickel (Ni), 0.1 to 6 wt% molybdenum (Mo), 0.1 to A stainless steel separator for a fuel cell, characterized in that it is a stainless steel sheet containing 5 wt% tungsten (W), 0.1 to 2 wt% tin (Sn), 0.1 to 2 wt% copper and iron (Fe) in the remaining amount. The method of claim 12, Corrosion current of the stainless steel separator plate for fuel cells is less than 1 kW / ㎠, the contact resistance is a stainless steel separator plate for fuel cells, characterized in that it has a value of less than 20mPa · ㎠.

Images