KR20090067960A - Coating method of anti-corrosion for sepertator of molten cabonate fuel cell - Google Patents

Abstract

An anti-corrosive coating method for separator for molten carbonate fuel cell is provided to simplify the manufacturing process using screen printing method without post treatment and washing of separator with low price. An anti-corrosive coating method of separator for molten carbonate fuel cell comprises: a step of adding chromium powder with nickel powder to make mixture metal powder; a step of adding an organic additive to the mixture metal powder to make nickel-chromium paste; a step of coating the nickel-chromium paste on the separator surface; and a step of heating the coated separator in the reductive atmosphere at 850 ~ 900°C. The organic additive is selected from ethyl cellulose, ethylene glycol and terpineol.

Description

Corrosion-resistant coating method for separator plate for molten carbonate fuel cell {COATING METHOD OF ANTI-CORROSION FOR SEPERTATOR OF MOLTEN CABONATE FUEL CELL}

The present invention relates to a corrosion-resistant coating method for a separator plate for a molten carbonate fuel cell by screen printing, and more particularly, by coating a nickel paste containing chromium on a separator plate of a molten carbonate fuel cell by a screen printing method. A method of coating an anti-corrosion layer on an anode of a separator for a fuel cell.

In general, a fuel cell refers to a device that generates electricity by electrochemically reacting chemical energy (hydrogen in fuel) contained in fuel with oxygen in air. Dual molten carbonate fuel cell is a fuel cell operated at 550 ~ 700 ℃, as shown in Figure 1, the electrode (electrode, cathode), the electrochemical reaction is carried out, between the electrodes to support the liquid carbonate as an electrolyte It consists of a separator plate that connects the flow of electricity and the matrix and the reaction gas. On the other hand, the separator is composed of a bipolar plate (bipolar plate), a current collector (current collector) and a wet seal (wet seal).

Since the molten carbonate fuel cell is operated at a high temperature of 550 ~ 700 ℃ it is easy to dissolve components and corrosion. In particular, this corrosion occurs seriously in the separator of the wet seal that comes into contact with the electrolyte. If such corrosion occurs, the electrolyte is lost, causing cross-over of the reaction gas and short circuit of the battery due to corrosion products, thereby shortening the performance and the sleep of the battery.

In order to solve this problem, various types of corrosion resistant alloys have been examined as a separator for molten carbonate fuel cells, and in particular, inexpensive austenitic stainless 310S and 316L are known to be somewhat suitable materials. However, these 310S and 316L have some effect on the corrosion protection which occurs at the cathode, but they do not have enough corrosion resistance to the corrosion which occurs at the anode. Thus, there is a need for a protective coating with a material such as nickel that has stronger corrosion resistance.

Until now, nickel coating of corroded plates for molten carbonate fuel cells has been mainly performed by electrolytic nickel plating, cladding and electroless nickel coating.

Dual electroplating allows a very high purity coating, but the coating thickness is not uniform, the non-uniform thickness distribution appears in the separator, and the coating layer is not dense. Nickel cladding, on the other hand, has relatively good characteristics, but has some disadvantages in that some chromium oxide is formed in the cladding, and the process is complicated and very expensive. In addition, the electroless plating has excellent thickness uniformity, but has a problem in that its use is limited because of its low stability and high cost.

The present invention has been made to solve the above problems, and an object thereof is to provide a corrosion resistant coating method of a separator plate for a molten carbonate fuel cell having a low manufacturing cost, a simple process, and an excellent coating quality.

The present invention comprises the steps of preparing a mixed metal powder by adding chromium powder to the nickel powder to achieve the above object; Preparing an nickel-chromium paste by adding an organic additive to the mixed metal powder; Coating the nickel-chromium paste on a surface of the separator plate for molten carbonate fuel cell by screen printing; And it provides a corrosion-resistant coating method of the separator plate for molten carbonate fuel cell comprising the step of heat-treating the nickel-chromium-coated separator in a reducing atmosphere at a temperature of 850 to 900 ℃.

At this time, the chromium powder is preferably added in an amount of 10 to 50% by weight based on the total weight of the mixed metal powder. Moreover, it is preferable that the average particle diameter of the said nickel powder is 3 micrometers or less.

In addition, the organic additive is at least one selected from the group consisting of ethyl cellulose, ethylene glycol, terpineol, and 10 to 40 parts by weight based on 100 parts by weight of the mixed metal powder. It is preferred to add in quantity.

In addition, the heat treatment is preferably performed in a hydrogen atmosphere.

The method of manufacturing a molten carbonate fuel cell of the present invention has the advantage of low manufacturing cost and simple manufacturing process using a screen printing method that does not require washing and post-treatment of the separator.

As described above, the corrosion-resistant coating method of the separator for molten carbonate fuel cell of the present invention comprises the steps of preparing a mixed metal powder by adding chromium powder to the nickel powder; Preparing an nickel-chromium paste by adding an organic additive to the mixed metal powder; Coating the nickel-chromium paste on a surface of the separator plate for molten carbonate fuel cell by screen printing; And heat-treating the nickel-chromium coated separator at a temperature of 850 to 900 ° C. in a reducing atmosphere.

Hereinafter, the present invention will be described in more detail.

First, a mixed metal powder is prepared by adding chromium powder to nickel powder. The chromium powder is added to densify the nickel coating layer formed on the separator, and the amount of the chromium powder is preferably about 10 to 50% by weight based on the total weight of the mixed metal powder. If the content of chromium is less than 10% by weight, there is a disadvantage that nickel is not sufficiently densified. If the content of chromium is more than 50% by weight, the chromium content is too high to form a dense and continuous nickel layer. .

In addition, in the present invention, it is preferable to use a nickel powder having an average particle diameter of 3 μm or less. If the particle size of the nickel powder is larger than 3 μm, it becomes difficult to form a dense and continuous nickel layer at a temperature of 850 to 900 ° C., which is not suitable. Because.

Next, an organic additive is added to the mixed metal powder made as described above and mixed to prepare a nickel-chromium paste.

In this case, the organic additive is added to make the mixed metal powder into a paste having viscosity and fluidity. In the present invention, ethyl cellulose, ethylene glycol, terpineol, and the like may be used as the organic additive.

At this time, the addition amount of the organic additive is preferably added in an amount of 10 to 40 parts by weight based on 100 parts by weight of the mixed metal powder. If the organic additive is added in an amount less than 10 parts by weight, a paste suitable for screen printing cannot be prepared. If the amount is more than 40 parts by weight, the paste is coated on a separator plate, and then the heat treatment is performed on the separator plate. This is because residual carbon and other compounds remain.

When the nickel-chromium paste is manufactured by the above process, the nickel chromium paste prepared by screen printing is coated on the separator plate of the molten carbonate fuel cell.

Screen printing is a method of applying a paste-like material to a substrate with a certain thickness by using a plate making, it is easy to control the thickness, the method is simple, and additional processes such as washing or post-treatment of the separator plate after coating It has the advantage of not needing it.

Therefore, after making nickel excellent in corrosion resistance as a paste in the present invention and then screen printing the paste on the separator, the corrosion resistant coating of the separator can be easily performed by a simple method.

When the nickel-chromium paste is applied to the separator through a screen printing with a constant thickness, the separator coated with the nickel-chromium paste is heat-treated at a temperature of 850 ° C to 900 ° C in a reducing atmosphere. If the heat treatment temperature is lower than 850 ℃, nickel is not sufficiently sintered densification is not good, because if the heat treatment at a temperature higher than 900 ℃ may cause oxidation and deformation of the stainless steel plate.

In addition, the heat treatment is preferably carried out in a reducing atmosphere. Here, the reducing atmosphere refers to a state in which the surroundings are surrounded by a substance that can easily give hydrogen or electrons, and typically a hydrogen atmosphere corresponds to a reducing atmosphere. Although the nickel layer is formed on the separator even when the heat treatment is performed in an air atmosphere other than the reducing atmosphere, the heat treatment is performed in the reducing atmosphere, thereby forming a continuous and uniform coating layer, which has an advantage of excellent coating quality.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the following examples are illustrative of the present invention for description, and the present invention is not limited by the following examples.

Comparative example  One

Nickel powder having an average particle size of 3 μm and chromium powder (average particle diameter of 1 to 5 mm, 99.5%) were mixed at a weight ratio of 9: 1 to form a mixed metal powder.

 30 parts by weight of an organic additive (trade name Organic vehicle 449, Electro-Science Laboratories, Inc.) was added to 100 parts by weight of the mixed metal powder, followed by mixing for 30 minutes in a conditioning mixer to prepare a nickel-chromium paste. The nickel paste thus prepared was screen-printed to a predetermined thickness with stainless steel sheave 200 mesh on stainless 316L (50 horizontal, 50 vertical, 0.5 mm thick), and then dried at 80 ° C. Then, the stainless specimen coated with nickel-chromium paste was heat-treated at 800 ° C. for 3 hours in a nitrogen atmosphere to form a nickel-chromium coating layer. The cross section of the nickel-chromium coating layer formed by the above process was observed with a scanning electron microscope, and the results are shown in Table 1. Meanwhile, FIG. 2 shows a cross section of the coating layer taken by the scanning electron microscope.

Comparative example  2

A nickel-chromium coating layer was formed in the same manner as in Comparative Example 1 except that the heat treatment was performed in a hydrogen atmosphere. The cross section of the formed coating layer was observed with a scanning electron microscope, and the results are shown in Table 1. Meanwhile, FIG. 3 shows a cross section of the coating layer taken by the scanning electron microscope.

Example  One

A nickel-chromium coating layer was formed in the same manner as in Comparative Example 1 except that the stainless specimen coated with the nickel-chromium paste was heat-treated at 850 ° C. for 12 hours in a nitrogen atmosphere. The cross section of the nickel-chromium coating layer formed by the above process was observed with a scanning electron microscope, and the results are shown in Table 1.

Example  2

A nickel-chromium coating layer was formed in the same manner as in Comparative Example 1 except that the stainless specimen coated with nickel-chromium paste was heat-treated at 850 ° C. for 6 hours in a hydrogen atmosphere. The cross section of the nickel-chromium coating layer formed by the above process was observed with a scanning electron microscope, and the results are shown in Table 1. On the other hand, Figure 4 shows the coating layer cross section taken by the scanning electron microscope.

Example  3

A nickel-chromium coating layer was formed in the same manner as in Comparative Example 1 except that the stainless specimen coated with nickel-chromium paste was heat-treated at 900 ° C. for 3 hours in a hydrogen atmosphere. The cross section of the nickel-chromium coating layer formed by the above process was observed with a scanning electron microscope, and the results are shown in Table 1. Meanwhile, FIG. 5 shows a cross section of the coating layer taken by the scanning electron microscope.

nickel chrome Binder atmosphere Sintering Condition result Cross section Comparative Example 1 90 10 30 nitrogen 800 ℃, 3 hours No densification 2 Comparative Example 2 90 10 30 Hydrogen 800 ℃, 3 hours No densification 3 Inventive Example 1 90 10 30 nitrogen 850 ° C, 12 hours Almost compact - Inventive Example 2 90 10 30 Hydrogen 850 ° C, 6 hours Full densification 4 Inventive Example 3 90 10 30 Hydrogen 900 ° C, 3 hours Full densification 5

As shown in Table 1, Figures 2 and 3, in Comparative Example 1 and Comparative Example 2 sintered at 800 ℃, although the nickel layer was formed regardless of the atmosphere, the continuous and uniform layer was not formed. However, as shown in FIGS. 4 and 5, in the embodiments manufactured by the method of the present invention, the nickel layer forms a continuous nickel layer indistinguishable from the stainless base metal to form a very good nickel coating layer, and hydrogen It can be seen that these characteristics are better represented in the atmosphere.

1 is a cross-sectional view of a molten carbonate fuel cell.

2 is a cross-sectional view of the nickel-chromium coating layer formed by Comparative Example 1 taken with a scanning electron microscope.

3 is a cross-sectional view of the nickel-chromium coating layer formed by Comparative Example 2 taken with a scanning electron microscope.

4 is a cross-sectional view of the nickel-chromium coating layer formed by Example 2 taken with a scanning electron microscope.

5 is a cross-sectional view of the nickel-chromium coating layer formed by Example 3 taken with a scanning electron microscope.

Claims (6)

Preparing a mixed metal powder by adding chromium powder to the nickel powder; Preparing an nickel-chromium paste by adding an organic additive to the mixed metal powder; Coating the nickel-chromium paste on a surface of the separator plate for molten carbonate fuel cell by screen printing; And The nickel-chromium-coated separator is heat-resistant coating method comprising the step of heat treatment at a temperature of 850 to 900 ℃ in a reducing atmosphere. The method of claim 1, The chromium powder is added in an amount of 10 to 50% by weight based on the total weight of the mixed metal powder corrosion resistant coating method of the separator plate for molten carbonate fuel cell. The method of claim 1, The corrosion resistance coating method of the separator plate for molten carbonate fuel cell, characterized in that the average particle diameter of the nickel powder is 3㎛ or less. The method of claim 1, The organic additive is an anti-corrosion coating method of the separator for molten carbonate fuel cell, characterized in that at least one selected from the group consisting of ethyl cellulose, ethylene glycol, terpineol. The method of claim 1, And the organic additive is added in an amount of 10 to 40 parts by weight based on 100 parts by weight of the mixed metal powder. The method of claim 1, The reducing atmosphere is a hydrogen atmosphere corrosion resistant coating method of the separator plate for molten carbonate fuel cell, characterized in that.

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