Patent ID: 11923580
Assignee: POSCO CO., LTD
Field: Materials, metallurgy (Chemistry)
Classification: CPC H  C  Y | IPC C  H

Claim 3:
4. A stainless steel for a fuel cell separator plate comprising:
a stainless base material and
a passive film formed on the stainless base material, wherein a content of Si atoms in the passive film is less than or equal to 0.1 at %, a Cr/Fe atomic weight ratio in the passive film is greater than or equal to 1.0, and the passive film has a corrosion potential of 0.3 VSCE or more,
wherein the Cr/Fe atomic weight ratio at an interface between the stainless steel base material and the passive film is greater than or equal to 0.65,
wherein the stainless base material at a region starting from 0.5 nm from the interface between the stainless base material and the passive film to 1 nm from the interface between the stainless base material and the passive film after film modification has the Cr/Fe atomic weight ratio of 0.45 or more, and
wherein the interface between the passive film and the stainless base material refers to a point in the stainless base material at which a content of oxygen accounted for 50% with respect to a maximum content of oxygen as determined in an elemental distribution measured in a thickness direction of the stainless steel, and
wherein the stainless steel for the fuel cell separator plate comprises C at greater than 0 to 0.02 wt %, N at greater than 0 to 0.02 wt %, Si at greater than 0 to 0.4 wt %, Mn at greater than 0 to 0.2 wt %, P at greater than 0 to 0.04 wt %, S at greater than 0 to 0.02 wt %, Cr at 25 to 34 wt %, Mo at 0 to less than 0.1 wt %, Cu at 0 to 1 wt %, Ni at 0 to less than 0.2 wt %, Ti at greater than 0 to 0.5 wt %, Nb at greater than 0 to 0.5 wt %, and the balance of Fe and other inevitable impurities.