Corrosion behaviors and contact resistances of the low-carbon steel bipolar plate with a chromized coating containing carbides and nitrides

This work improved the surface performance of low-carbon steel AISI 1020 by a reforming pack chromization process at low temperature (700 °C) and investigated the possibility that the modified steels are used as metal bipolar plates (BPP) of PEMFCs. The steel surface was activated by electrical discharge machining (EDM) with different currents before the chromizing procedure. Experimental results indicate that a dense and homogenous Cr-rich layer is formed on the EDM carbon steels by pack chromization. The chromized coating pretreated with electrical discharge currents of 2 A has the lowest corrosion current density, 5.78 × 10−8 Acm−2, evaluated by potentiodynamic polarization in a 0.5 M H2SO4 solution and the smallest interfacial contact resistance (ICR), 11.8 mΩ-cm2, at 140 N/cm2. The carbon steel with a coating containing carbides and nitrides is promising for application as metal BPPs, and this report presents the first research in producing BPPs with carbon steels.