Stainless steel having excellent surface electrical conductivity for fuel cell separator and method for manufacturing same

Patent metadata

Field	Value
Publication number	US-2023066817-A1
Application number	US-202017785702-A
Country	US
Kind code	A1
Filing date	Oct 19, 2020
Priority date	Dec 19, 2019
Publication date	Mar 2, 2023
Grant date	—

Abstract

Disclosed is a stainless steel having excellent surface electrical conductivity for a fuel cell separator. According to an embodiment of the disclosed stainless steel having excellent surface electrical conductivity for a fuel cell separator, a value of the following surface oxide atomic ratio (1) may be 0.08 or more, as measured on the surface of a stainless steel containing 15 wt % or more of Cr by X-ray angle-resolved photoemission spectroscopy using an Al-Kα X-ray source under the condition where a take-off angle of photoelectrons is from 12° to 85°.sum⁢of⁢atomic⁢concentrations⁢(at⁢%)⁢of⁢Cr⁢in⁢Cr⁢hydroxidesum⁢of⁢atomic⁢concentrations⁢(at⁢%)⁢of⁢metal⁢elementsin⁢total⁢oxides⁢and⁢hydroxides(1)The Cr hydroxide represents CrOOH, Cr(OH)2, or Cr(OH)3. The total oxides and hydroxides include a Cr oxide, the Cr hydroxide, an Fe oxide, an Fe hydroxide, and a metal oxide (MO), and the metal oxide (MO) includes a mixed oxide, wherein M represents an alloying element other than Cr and Fe or a combination thereof in a matrix, and O represents oxygen.

First claim

1 . A stainless steel having excellent surface electrical conductivity for a fuel cell separator,
wherein a value of the following surface oxide atomic ratio (1) is 0.08 or more, as measured on a surface of the stainless steel containing 15 wt % or more of Cr by X-ray angle-resolved photoemission spectroscopy using an Al-Kα X-ray source under the condition where a take-off angle of photoelectrons is from 12° to 85°:

sum
⁢

of
⁢

atomic
⁢

concentrations
⁢

(

at
⁢

%

)

⁢

of
⁢

Cr
⁢

in
⁢

Cr
⁢

hydroxide

sum
⁢

of
⁢

atomic
⁢

concentrations
⁢

(

at
⁢

%

)

⁢

of
⁢

metal
⁢

elements

in
⁢

total
⁢

oxides
⁢

and
⁢

hydroxides

(
1
)

wherein the Cr hydroxide represents CrOOH, Cr(OH) 2 , or Cr(OH) 3 , and
the total oxides and hydroxides include a Cr oxide, the Cr hydroxide, an Fe oxide, an Fe hydroxide, and a metal oxide (MO), and the metal oxide (MO) includes a mixed oxide, wherein M represents an alloying element other than Cr and Fe or a combination thereof in a matrix, and O represents oxygen.

2 . The stainless steel according to claim 1 , wherein the value of the surface oxide atomic ratio (1) is 0.2 or more.

3 . The stainless steel according to claim 1 , wherein a bandgap energy of a surface oxide layer of the stainless steel is 2 eV or less.

4 . The stainless steel according to claim 1 , wherein the surface oxide layer of the stainless steel forms an ohmic contact with the matrix.

5 . A method for manufacturing the stainless steel having excellent surface electrical conductivity for a fuel cell separator according to claim 1 , the method comprising:
a primary surface treatment performed by immersing a cold-rolled stainless steel sheet in a nonoxidizing acid solution, or conducting an electrolytic treatment after the immersing, and a secondary surface treatment performed by immersing the cold-rolled stainless steel sheet in an oxidizing acid solution.

6 . The method according to claim 5 , wherein the primary surface treatment comprises immersing the cold-rolled stainless steel sheet in the nonoxidizing acid solution for 5 seconds or more, or performing an electrolytic treatment with a current density of 0.1 A/cm 2 or more for 5 seconds or more after the immersing, and
the nonoxidizing acid solution is a 5 wt % or more hydrochloric acid or sulfuric acid solution at 50° C. or higher.

7 . The method according to claim 5 , wherein the secondary surface treatment comprises immersing the cold-rolled stainless steel sheet in the oxidizing acid solution for 5 seconds or more, and
the oxidizing acid solution is a 5 wt % or more nitric acid solution at 50° C. or higher.

Assignees

• Posco

Inventors

• Kim Jong-Hee
• Seo Bo-Sung
• Kim Jin-Suk

Classifications

• H01M8/0228

  in the form of layered or coated products · CPC title

• C21D9/46

  for sheet metals · CPC title

• C22C38/26

  with niobium or tantalum · CPC title

• C21D8/0278

  involving a particular surface treatment  (C21D8/0294 takes precedence) · CPC title

• C22C38/50

  with titanium or zirconium · CPC title