Effects of low-temperature nitridation on the electrical conductivity and corrosion resistance of 446M stainless steel as bipolar plates for proton exchange membrane fuel cell

Low-temperature nitridation was used to form a protective and conductive layer on stainless steel. The surface characterization reveals that a continuous and protective Cr-nitride/oxide layer (CrN and Cr(2)O(3)) forms on the 446M stainless steel surface after low-temperature nitridation. The electrical conductivity of the sample is investigated in terms of the interfacial contact resistance. This value for nitrided 446M at low temperature is 6 m Omega cm(2), which is much lower than that of the bare 446M stainless steel (about 77 m Omega cm(2)) at a compaction force of 140N/cm(2). The corrosion resistance of low-temperature nitrided 446M stainless steel is examined in potentiodynamic and potentiostatic tests under simulated polymer electrolyte membrane fuel cell (PEMFC) conditions with pH 3 H(2)SO(4) at 80 degrees C. In a simulated anode condition, the current density is -1 x 10(-6) A/cm(2). In a simulated cathode condition, the current density is 1 x 10(-7) A/cm(2). Low-temperature nitrided 446M stainless steel shows superior electrical conductivity and corrosion resistance than bare 446M stainless steel. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.