A molybdenum nitride diffusion coating has been prepared on the surface of AISI 304 stainless steel (304 SS) by plasma surface diffusion alloying method as bipolar plate for proton exchange membrane fuel cell (PEMFC). X-ray diffraction data shows that the molybdenum nitride is face-centered-cubic Mo2N phase. The results of scanning electron microscopy in combination with energy-dispersive X-ray analysis spectrometer indicate that the as-prepared molybdenum nitride diffusion coating consists of a similar to 3.5 mu m surface layer (molybdenum nitride) and a similar to 0.5 mu m subsurface layer (Mo and N solid solution). In addition, the average contact angle with water for modified 304 SS is 91 degrees, demonstrating the better hydrophobic property of the surface modified 304 SS as compared to the untreated ones with average contact angle of 68 degrees. Potentiodynamic and potentiostatic testing in simulated PEFMC operating conditions (0.05 M H2SO4 + 2 ppm F- solution at 70 degrees C purged with either hydrogen or air) as well as interfacial contact resistance (ICR) measurement imply that the molybdenum nitride modified 304 SS exhibits improved corrosion resistance and promising ICR. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.