Method for producing stainless steel for fuel cell separator, stainless steel for fuel cell separator, fuel cell separator, and fuel cell

Patent metadata

Field	Value
Publication number	US-9653738-B2
Application number	US-201113979700-A
Country	US
Kind code	B2
Filing date	Jan 19, 2011
Priority date	Jan 17, 2011
Publication date	May 16, 2017
Grant date	May 16, 2017

Abstract

A stainless steel for use in a fuel cell separator is produced by subjecting stainless steel containing 16 mass % or more of Cr to electrolytic treatment and thereafter to immersion treatment in a solution containing fluorine. The electrolytic treatment is carried out by anodic electrolyzation or by a combination of anodic electrolyzation and cathodic electrolyzation, and an anodic electrolytic quantity Qa and a cathodic electrolytic quantity Qc preferably satisfy Qa≧Qc. The solution containing fluorine preferably has a temperature of 40° C. or higher, and hydrofluoric acid concentration [HF] (mass %) and nitric acid concentration [HNO 3 ] (mass %) satisfying [HF]≧0.8×[HNO 3 ].

First claim

The invention claimed is:

1. A method of producing stainless steel for use in a fuel cell separator, wherein stainless steel containing 16 mass % or more of Cr comprising subjecting the stainless steel to electrolytic treatment and thereafter to immersion treatment in a solution containing fluorine and an Fe ion concentration of 0.04 g/l or more,
wherein the solution containing fluorine is hydrofluoric acid or a mixture of nitric acid and hydrofluoric acid having a hydrofluoric acid concentration [HF] (mass %) and a nitric acid concentration [HNO 3 ] (mass %) satisfying: [HF]≧0.8×[HNO 3 ], [HNO 3 ] including 0 with a proviso that, if [HNO 3 ] is 0, then [HF] is greater than 0, and
wherein electrolytic treatment is carried out in at least one of an acid containing 0.5 mass % or more of sulfuric acid and a solution containing 5 mass % or more of sodium sulfate.

2. The method according to claim 1 , wherein the electrolytic treatment is carried out by anodic electrolyzation or by a combination of anodic electrolyzation and cathodic electrolyzation; and an anodic electrolytic quantity Qa in C/dm 2 and a cathodic electrolytic quantity Qc in C/dm 2 satisfy relationship: Qa≧Qc having relationship: Qc=0 when electrolytic treatment is carried out by anodic electrolyzation alone with a proviso that, if Qc=0, then Qa>Qc.

3. The method according to claim 1 , wherein a temperature of the solution containing fluorine is 40° C. or higher.

4. The method according to claim 1 , wherein the solution containing fluorine is hydrofluoric acid or a mixture of nitric acid and hydrofluoric acid having a hydrofluoric acid concentration [HF] (mass %) and a nitric acid concentration [HNO 3 ] (mass %) satisfying: [HF]≧1.7×[HNO 3 ], [HNO 3 ] including 0 with a proviso that, if [HNO 3 ] is 0, then [HF] is greater than 0.

5. The method according to claim 1 , wherein the solution containing fluorine is hydrofluoric acid or a mixture of nitric acid and hydrofluoric acid having a hydrofluoric acid concentration [HF] (mass %) and a nitric acid concentration [HNO 3 ] (mass %) satisfying: [HF]≧5.0×[HNO 3 ], [HNO 3 ] including 0 with a proviso that, if [HNO 3 ] is 0, then [HF] is greater than 0.

6. The method according to claim 2 , wherein a temperature of the solution containing fluorine is 40° C. or higher.

7. The method according to claim 2 , wherein the solution containing fluorine is hydrofluoric acid or a mixture of nitric acid and hydrofluoric acid having a hydrofluoric acid concentration [HF] (mass %) and a nitric acid concentration [HNO 3 ] (mass %) satisfying: [HF]≧1.7×[HNO 3 ], [HNO 3 ] including 0 with a proviso that, if [HNO 3 ] is 0, then [HF] is greater than 0.

8. The method according to claim 3 , wherein the solution containing fluorine is hydrofluoric acid or a mixture of nitric acid and hydrofluoric acid having a hydrofluoric acid concentration [HF] (mass %) and a nitric acid concentration [HNO 3 ] (mass %) satisfying: [HF]≧1.7×[HNO 3 ], [HNO 3 ] including 0 with a proviso that, if [HNO 3 ] is 0, then [HF] is greater than 0.

9. The method according to claim 2 , wherein the solution containing fluorine is hydrofluoric acid or a mixture of nitric acid and hydrofluoric acid having a hydrofluoric acid concentration [HF] (mass %) and a nitric acid concentration [HNO 3 ] (mass %) satisfying: [HF]≧5.0×[HNO 3 ], [HNO 3 ] including 0 with a proviso that, if [HNO 3 ] is 0, then [HF] is greater than 0.

10. The method according to claim 3 , wherein the solution containing fluorine is hydrofluoric acid or a mixture of nitric acid and hydrofluoric acid having a hydrofluoric acid concentration [HF] (mass %) and a nitric acid concentration [HNO 3 ] (mass %) satisfying: [HF]≧5.0×[HNO 3 ], [HNO 3 ] including 0 with a proviso that, if [HNO 3 ] is 0, then [HF] is greater than 0.

Assignees

• Ide Shinsuke
• Ishii Tomohiro
• Ishikawa Shin
• Kato Yasushi
• Jfe Steel Corp

Inventors

• Ide Shinsuke
• Ishii Tomohiro
• Ishikawa Shin
• Kato Yasushi

Classifications

• Y02P70/50

  Manufacturing or production processes characterised by the final manufactured product · CPC title

• H01M8/021 Primary

  Alloys based on iron · CPC title

• C23C8/80

  After-treatment · CPC title

• C25F3/00

  Electrolytic etching or polishing · CPC title

• Y02E60/50

  Fuel cells · CPC title