Stainless steel separator for fuel cells, method for making the same, and solid polymer fuel cell including the same

A stainless steel separator for fuel cells having gas channels including grooves and projections for partitioning the grooves, the separator having a composition comprising:

• about 0.03 mass percent or less of carbon;
• about 0.03 mass percent or less of nitrogen, the total content of carbon and nitrogen being about 0.03 mass percent or less;
• about 16 mass percent to about 45 mass percent chromium, and
• about 0.1 mass percent to about 3.0 mass percent molybdenum,
• wherein the separator has a contact resistance of about 100 mμ·cm2 or less;
• and
• a BA film having a thickness in the range of about 10 to about 300 nm on a surface of at least some of the projections.

A method for making a stainless steel separator for fuel cells having gas channels including grooves and projections for partitioning the grooves comprising:

• hot-rolling a slab to form a hot-rolled sheet having a predetermined thickness, the slab comprising about 0.03 mass percent or less of carbon, about 0.03 mass percent or less of nitrogen, the total content of carbon and nitrogen being about 0.03 mass percent or less, about 15 mass percent to about 45 mass percent chromium, and about 0.1 mass percent to about 3.0 mass percent molybdenum;
• annealing and pickling the hot-rolled sheet;
• and
• cutting the hot-rolled sheet to form the stainless steel separator.

A method for making a stainless steel separator for fuel cells having gas channels including grooves and projections for partitioning the grooves comprising:

• hot-rolling a slab to form a hot-rolled sheet having a predetermined thickness, the slab comprising about 0.03 mass percent or less of carbon, about 0.03 mass percent or less of nitrogen, the total content of carbon and nitrogen being about 0.03 mass percent or less, about 16 mass percent to about 45 mass percent chromium, and about 0.1 mass percent to about 3.0 mass percent molybdenum;
• annealing and pickling the hot-rolled sheet;
• cold-rolling the hot-rolled sheet to form a cold-rolled sheet having a predetermined thickness;
• press-forming the cold-rolled sheet to form the stainless steel separator, wherein surface roughness of projections applied to the sheet is adjusted so that the arithmetic average surface roughness Ra is in the range of about 0.01 to about 1.0 μm and the maximum height Ry is in the range of about 0.01 to about 20 μm.