Surface modification of stainless steel bipolar plates for PEMFC (proton exchange membrane fuel cell) application

Stainless steel 316 and 304 plates were deposited with a metallic film (top layer) and a conductive oxide film (intermediate layer) by a sputtering method and an E-beam method, respectively. The conductive oxide film was formed on the stainless steel plates in the range of thickness of 200, 400, and 600 nm. The XRD patterns of the conductive oxide films showed a typical indium-tin oxide (ITO) crystalline phase. The metallic films of 100 nm thickness were subsequently formed on the surface region of the bare stainless steel plates and the stainless steel plates deposited with ITO thin film. Surface morphologies of the stainless steel bipolar plates deposited with conductive film and metallic film were observed by AFM and FE-SEM. The metallic films on the stainless steel plates represented the microstructural morphology of the fine columnar grains of 10 nm diameter and 60 nm length. The electrical resistivity and contact angle of the stainless steel bipolar plates modified were examined as a function of the thickness of the conductive oxide film.