| CPC C23C 22/06 (2013.01) [C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/20 (2013.01); C22C 38/22 (2013.01); C22C 38/24 (2013.01); C22C 38/26 (2013.01); C22C 38/28 (2013.01); C23C 22/78 (2013.01); C25F 1/06 (2013.01); H01M 8/021 (2013.01); H01M 8/0228 (2013.01)] | 2 Claims |
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1. A method of manufacturing a stainless steel for a polymer fuel cell separator, the method comprising:
electrolyzing to remove a first passivation film formed on a cold-rolled sheet of a stainless steel comprising, in percent (%) by weight of the entire composition, C: greater than 0 to 0.1%, N: greater than 0 to 0.02%, Si: greater than 0 to 0.25%, Mn: greater than 0 to 0.2%, P: greater than 0 to 0.04%, S: greater than 0 to 0.02%, Cr: 29.7 to 30.1%, Ti: greater than 0 to 0.5%, Nb: greater than 0 to 0.5%, the remainder of iron (Fe) and inevitable impurities; and
immersing in an acid solution to form a second passivation film on the stainless cold-rolled sheet,
wherein the electrolyzing is performed in 5 to 30% by weight of sulfuric acid solution at 40 to 80° C. and a cathode applied current density (Ic) is 4 to 15 A/dm2,
the immersing in the acid solution is performed in 10 to 15% by weight of nitric acid at 40 to 60° C.,
the acid solution does not comprise hydrofluoric acid,
a contact resistance of the second passivation film is 18.2 mΩcm2 or less, and
no surface rust is found on a surface of the polymer fuel cell separator after performing a static potential endurance test at 0.6V for 300 hours.
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