Provided is a ferritic stainless steel sheet for current collectors for sulfide-based solid-state batteries, which has excellent sulfidation resistance and adhesiveness. The ferritic stainless steel sheet has a component composition containing Cr in an amount of 16% by mass or more, wherein the surface of the ferritic stainless steel sheet has an uneven structure having recessed portions and projecting portions, the average height of the projecting portions is 20 to 50 nm inclusive, the average distance between the projecting portions is 20 to 200 nm inclusive, and the [Cr]/[Fe], i.e., the ratio of the atom concentration of Cr that is present in a form other than the metal form to the atom concentration of Fe that is present in a form other than the metal form, on the surface of the ferritic stainless steel sheet is 1.0 or more.

Provided is a ferritic stainless steel sheet for current collectors for sulfide-based solid-state batteries, which has excellent sulfidation resistance and adhesiveness. The ferritic stainless steel sheet has a component composition containing Cr in an amount of 16% by mass or more, wherein the surface of the ferritic stainless steel sheet has an uneven structure having recessed portions and projecting portions, the average height of the projecting portions is 20 to 50 nm inclusive, the average distance between the projecting portions is 20 to 200 nm inclusive, and the [Cr]/[Fe], i.e., the ratio of the atom concentration of Cr that is present in a form other than the metal form to the atom concentration of Fe that is present in a form other than the metal form, on the surface of the ferritic stainless steel sheet is 1.0 or more.

The present invention provides a chromium-containing steel sheet for a current collector of a nonaqueous electrolyte secondary battery which has excellent corrosion resistance in a battery environment and, when used as a current collector of a nonaqueous electrolyte secondary battery, which enables the nonaqueous electrolyte secondary battery to have excellent cycle characteristics.

A chromium-containing steel sheet for a current collector of a nonaqueous electrolyte secondary battery has a chemical composition containing 10% by mass or more of Cr. The chromium-containing steel sheet has an irregular structure including recesses and protrusions at a surface thereof. The average height of the protrusions is 20 nm or more and 100 nm or less, and the average spacing between the protrusions is 20 nm or more and 300 nm or less.

An austenitic stainless steel sheet for fuel cell separators comprises a textured structure at a surface of the stainless steel sheet, the textured structure having recessed parts and projected parts, an average height of the projected parts being 30 nm or more and 300 nm or less, and an average interval between the projected parts being 20 nm or more and 350 nm or less, wherein a ratio [Cr]/[Fe] of an atomic concentration of Cr existing in chemical form other than metal to an atomic concentration of Fe existing in chemical form other than metal at the surface of the stainless steel sheet is 1.0 or more.

Disclosed is a method of manufacturing a stainless steel with excellent contact resistance for a polymer fuel cell separator. The method of manufacturing a stainless steel with excellent contact resistance for a polymer fuel cell separator according to an embodiment of the present disclosure includes: electrolyzing to remove a first passivation film formed on a cold-rolled thin 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: 22 to 34%, Ti: greater than 0 to 0.5%, Nb: greater than 0 to 0.5%, the remainder of iron (Fe) and other inevitable impurities; and immersing in a mixed acid solution of nitric acid and hydrofluoric acid to form a second passivation film on the stainless cold-rolled thin sheet.

Disclosed is a method of manufacturing a stainless steel with excellent contact resistance for a polymer fuel cell separator. The method of manufacturing a stainless steel with excellent contact resistance for a polymer fuel cell separator according to an embodiment of the present disclosure includes: electrolyzing to remove a first passivation film formed on a cold-rolled thin 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: 22 to 34%, Ti: greater than 0 to 0.5%, Nb: greater than 0 to 0.5%, the remainder of iron (Fe) and other inevitable impurities; and immersing in a mixed acid solution of nitric acid and hydrofluoric acid to form a second passivation film on the stainless cold-rolled thin sheet.

A stainless steel sheet for fuel cell separators comprises a predetermined chemical composition, wherein the stainless steel sheet has a textured structure at a surface thereof, an average interval between projected parts of the textured structure being 20 nm or more and 200 nm or less, and a ratio [Cr]/[Fe] of an atomic concentration of Cr existing in chemical form other than metal to an atomic concentration of Fe existing in chemical form other than metal at the surface of the stainless steel sheet is 2.0 or more.

A stainless steel sheet for fuel cell separators comprises a predetermined chemical composition, wherein the stainless steel sheet has a textured structure at a surface thereof, an average interval between projected parts of the textured structure being 20 nm or more and 200 nm or less, and a ratio [Cr]/[Fe] of an atomic concentration of Cr existing in chemical form other than metal to an atomic concentration of Fe existing in chemical form other than metal at the surface of the stainless steel sheet is 2.0 or more.

A hot-dip Sn—Zn-based alloy-plated steel sheet according to an aspect of the present invention includes: a steel sheet having a predetermined chemical composition; a diffusion alloy layer provided on one surface or both surfaces of the steel sheet; and a Sn—Zn-plated layer provided on the diffusion alloy layer, in which the diffusion alloy layer contains Fe, Sn, Zn, Cr, and Ni, an area ratio of a Sn—Fe—Cr—Zn phase to a Sn—Fe—Ni—Zn phase in the diffusion alloy layer is 0.01 or more and less than 2.5, the diffusion alloy layer has a coverage of 98% or more with respect to the one surface, the Sn—Zn-plated layer contains 1% to 20% of Zn by mass % and a remainder consisting of Sn and impurities, and an adhesion amount of the Sn—Zn-plated layer is 10 to 80 g/m.sup.2 per one surface.

A hot-dip Sn—Zn-based alloy-plated steel sheet according to an aspect of the present invention includes: a steel sheet having a predetermined chemical composition; a diffusion alloy layer provided on one surface or both surfaces of the steel sheet; and a Sn—Zn-plated layer provided on the diffusion alloy layer, in which the diffusion alloy layer contains Fe, Sn, Zn, Cr, and Ni, an area ratio of a Sn—Fe—Cr—Zn phase to a Sn—Fe—Ni—Zn phase in the diffusion alloy layer is 0.01 or more and less than 2.5, the diffusion alloy layer has a coverage of 98% or more with respect to the one surface, the Sn—Zn-plated layer contains 1% to 20% of Zn by mass % and a remainder consisting of Sn and impurities, and an adhesion amount of the Sn—Zn-plated layer is 10 to 80 g/m.sup.2 per one surface.