Tantalum nitride coated AISI 316L as bipolar plate for polymer electrolyte membrane fuel cell

Tantalum nitride (TaN) thin films are deposited on AISI 316L stainless steel by inductively coupled, plasma-assisted, reactive magnetron sputtering at various N2 flow rates. TaN film behavior is investigated in simulated polymer electrolyte membrane fuel cell (PEMFC) conditions by using electrochemical measurement techniques for application as bipolar plates. The results of a potentio-dynamic polarization test under PEMFC cathodic and anodic conditions indicate that the corrosion current density of the TaNx films is of the order of 10−7 A cm−2 (at 0.6 V) and 10−8 A cm−2 (at −0.1 V), respectively; these results are considerably better than the individual results for metallic Ta films and AISI 316L stainless steel. The TaNx films exhibit superior stability in a potentio-static polarization test performed under PEMFC cathodic and anodic conditions. The interfacial contact resistance of the films is measured in the range of 50–150 N cm−2, and the lowest value is 11 mΩ cm2 at a compaction pressure of 150 N cm−2.