Corrosion performance of austenitic stainless steel bipolar plates for Nafion- and room-temperature ionic-liquid-based PEMFCs

In this paper we study the corrosion of AISI 304 austenitic stainless steel PEMFC bipolar plates in aqueous and room-temperature ionic-liquid electrolytes. The anodic potential thresholds and dynamics have been investigated by electrochemical (potentiodynamic and potentiostatic) and in situ spectroelectrochemical methods (visible electroreflectance and VIS-UV spectroellipsometry). We measured the values of damage potentials and we followed the time evolution of corrosion current and reflectivity above and below the pitting potential, obtaining an accurate characterisation of the surface conditions under oxidative attack. The ability of AISI 304 to repassivate in Cl --containing aqueous solution as well as the amount of residual surface damage have been assessed quantitatively by following electrode reflectivity under applied potential. Outstanding inertness of AISI 304 in [BMP][TFSA] was proved. The results of this work show that low-cost AISI 304 is a promising interconnect material for both Nafion- and RTIL-based PEMFCs