Two different films, an external metallic film (100 nm) and a conductive interlayer (200-600 nm) have been applied to the surface of stainless steel 316, 304 plates by a sputtering method and an E-beam method, respectively. The metal nitride film was formed on the external surface regions of the two-film deposited stainless steel plates through a simple annealing procedure. The XRD patterns of the stainless steel plates deposited with the metallic film and a conductive oxide film showed the crystalline phase of a typical indium-tin oxide, a metallic phase and the metal substrate as well as external nitride film. The nitride film was composed of two metal nitride phases of CrN and Cr2N compounds. Surface microstructural morphologies of the multi-film deposited, stainless steel bipolar plates were observed by AFM and FE-SEM images. The metallic top film on the stainless steel plates showed a microstructural pattern composed of fine columnar grains with 10nm diameter and 60nm length in FE-SEM images. The electrical resistivity and contact angle of the coated-stainless steel bipolar plates were measured with the thickness of the oxide film.

Keywords: proton exchange membrane fuel cell (PEMFC); bipolar plates; conductive film; metallic film; metal nitride; resistivity