Stainless steel sheet for a separator for a solid polymer fuel cell and a solid polymer fuel cell employing the separator

Patent metadata

Field	Value
Publication number	US-9680162-B2
Application number	US-201113080937-A
Country	US
Kind code	B2
Filing date	Apr 6, 2011
Priority date	Oct 7, 2008
Publication date	Jun 13, 2017
Grant date	Jun 13, 2017

Abstract

A stainless steel member for a separator of a solid polymer fuel cell has excellent cell properties with little deterioration in performance over long periods of operation without worsening of the corrosion resistance of a stainless steel separator. The stainless steel member has a stainless steel base metal, and a passive film and electrically conductive precipitates both provided on a surface of the stainless steel base metal. The electrically conductive precipitate penetrates the passive film and includes a substance originating from the stainless steel base metal. An electrically conductive layer comprising a nonmetallic electrically conductive substance is preferably provided on the surface of the passive film, and the electrically conductive layer is preferably electrically connected to the stainless steel base member through the electrically conductive precipitates.

First claim

The invention claimed is:

1. A stainless steel member for a separator for a solid polymer fuel cell, the stainless steel base metal comprising:
a stainless steel base metal;
a passive film; and
smut;
wherein the passive film, which is a film of an electrically insulating oxide. and the smut are provided on a surface of the stainless steel base metal;

wherein the smut is a substance, originating from the stainless steel base metal, which has precipitated on or adhered to the surface of the stainless steel member as a result of pickling of the stainless steel base metal;
wherein the smut includes electrically conductive precipitates;
wherein a thickness of the smut is larger than a thickness of the passive film and the electrically conductive precipitates penetrate the passive film; and
wherein the passive film partially covers the smut on a surface of the stainless steel base material.

2. A stainless steel member as set forth in claim 1 wherein the electrically conductive precipitates are a polycrystalline substance containing O, S, Fe, Cr, and C as constituent elements.

3. A stainless steel member as set forth in claim 1 wherein an electrically conductive layer comprising a nonmetallic electrically conductive substance is provided on the surface of the passive film, and the electrically conductive layer is electrically connected to the stainless steel base metal through the electrically conductive precipitates.

4. A stainless steel member as set forth in claim 3 wherein the nonmetallic electrically conductive substance includes graphite-based carbon.

5. A stainless steel member as set forth in claim 4 wherein the graphite-based carbon provided on the surface of the passive film has an interplane spacing d002 of at most 3.390 Angstroms.

6. A stainless steel member as set forth in claim 5 wherein when peak strengths of diffraction lines of atomic planes obtained by wide angle x-ray diffraction measurement of crystals of the graphite-based carbon provided on the surface of the passive film are compared, a ratio of the peak strength of the diffraction line of a (110) atomic plane to the peak strength of the diffraction line of a (004) atomic plane is less than 0.1.

7. A stainless steel member as set forth in claim 4 wherein the electrically conductive layer is formed by rubbing a member containing graphite-based carbon against a surface comprising the surface of the passive film and the surface of the electrically conductive precipitates.

8. A stainless steel member as set forth in claim 7 wherein the average surface roughness Ra of the surface comprising the surface of the passive film and the surface of the electrically conductive precipitates is at least 0.10 micrometers.

9. A stainless steel member as set forth in claim 4 wherein the electrically conductive precipitates and the electrically conductive layer are formed at the same time by performing electrolysis treatment of a stainless steel substrate comprising the stainless steel base metal and the passive film in an acidic solution containing sulfuric acid ions while rubbing a member including graphite-based carbon which functions as a counter electrode in the electrolysis treatment on the member being treated.

10. A stainless steel member as set forth in claim 9 wherein the average surface roughness Ra of the surface of the stainless steel substrate is at least 0.10micrometers.

11. A solid polymer fuel cell having a separator obtained from a stainless steel member as set forth in claim 1 .

Assignees

• Kaminaka Hideya
• Imamura Junko
• Seki Akira
• Takeuchi Kouichi
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Kaminaka Hideya
• Imamura Junko
• Seki Akira
• Takeuchi Kouichi

Classifications

• H01M8/10

  Fuel cells with solid electrolytes · CPC title

• H01M2/14

  Electricity · mapped topic

• H01M8/0226

  in the form of mixtures · CPC title

• H01M8/021 Primary

  Alloys based on iron · CPC title

• H01M2008/1095

  Fuel cells with polymeric electrolytes · CPC title