AISI 304 stainless steel (SS) has been niobized by a plasma surface diffusion alloying method. A 3 mu m niobized layer with dominant niobium elements has been formed on the 304 SS surface and the performances of the niobized 304 SS has been examined and evaluated as bipolar plate for proton exchange membrane fuel cell (PEMFC). Results show that the average contact angle with water for the niobized 304 SS is about 90.4 degrees, demonstrating better hydrophobicity as compared with the untreated 304 SS (68.1 degrees). The corrosion resistance of the 304 SS is considerably improved by the niobized layer with the corrosion current densities decreased at 0.2 and 0.4 mu A cm(-2) in simulated PEMFC anode purged with hydrogen and the cathode purged with air condition (0.05 M H2SO4 + 2 ppm F- solution at 70 degrees C), respectively. The interfacial contact resistance (ICR) for the as-prepared niobized 304 SS is 10.53 m Omega cm(2) at the compaction of 140 N cm(-2). Furthermore, after 4h potentiostatic tests, the niobizied specimens exhibit much lower ICR than that for the untreated ones. Thus, the niobized layer can act as a conductively protective layer of the 304 SS bipolar plate for PEMFC. (C) 2012 Elsevier B.V. All rights reserved.