Stainless steel bipolar plates for the polymer electrolyte membrane (PEM) fuel cell offer many advantages over conventional machined graphite. Austenitic stainless steel 316L is a traditional candidate for metal bipolar plates. However, the interfacial ohmic loss across the metallic bipolar plate and membrane electrode assembly due to corrosion decreases the overall power output of PEMFC. Plasma nitriding was applied to improve the surface performance of 316L bipolar plates. A dense gamma(N) phase layer was formed on the surface. Polarization curves in the solution simulating PEMFC environment and interfacial contact resistance were measured. The results show that the corrosion resistance is improved and the interfacial contact resistance (ICR) is decreased after plasma nitriding. In comparison with the untreated 316L, the ICR between the carbon paper and passive film for the plasma-nitfided 316L increases at the same condition and lowers with increasing pH value. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All fights reserved.