# US 7,608,119 B2 · Separator for low-temperature type fuel cell and production method therefor

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- Number: US 7,608,119 B2
- Document ID: US7608119B2
- Status: Granted
- Kind: B2
- Application number: 10/312,158
- Filed: 2001-09-07
- Published: 2003-09-11
- Granted: 2009-10-27
- Earliest claimed: 2000-09-12
- Assignees: Nisshin Steel Co., Ltd.
- Inventors: Tsutomu Miyano; Takeshi Shimizu; Keiji Izumi; Yoshikazu Morita; Shinichi Kamoshida; Toshiki Kingetsu
- Web page: https://patentgrep.com/patent/US7608119B2

## CPC

- H01M 8/021: Alloys based on iron
- C25F 3/06: of iron or steel
- Y02E 60/50: Fuel cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- Y10T 29/49115: including coating or impregnating
- Y10T 428/12389: having variation in thickness
- Y10T 428/12993: Surface feature [e.g., rough, mirror]
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- C25F: PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A stainless steel sheet useful as a separator for a low-temperature fuel cell has the surface state that a lot of fine projections (p) stand close together around many fine pits (d) formed over a whole surface. The surface state is realized by alternating electrolytic etching in a ferric chloride solution. When the stainless steel separator is built in a fuel cell, contact resistance between the separator and a graphite electrode is kept at a lower level even in a corrosive atmosphere. Consequently, the fuel cell can be driven with high power-generating efficiency over a long term even under severely corrosive conditions without generation of massive Joule heat.

## Claims

### Claim 1

A method of manufacturing a separator for a low-temperature fuel cell, comprising the step of:
roughening a surface of a stainless steel sheet by alternating electrolytic etching in a ferric chloride solution, so as to process said surface to include a plurality of fine projections standing close together around a plurality of fine pits.

### Claim 2 (depends on 1)

The method of claim 1, wherein the alternating electrolytic etching occurs for about at least 20 seconds.

### Claim 3 (depends on 1)

The method of claim 1, wherein alternating electrolytic etching includes forming a plurality of fine projections around a plurality of fine pits in a passive film composed of oxides and hydroxides coated on said surface of stainless steel sheet.