Increase in the corrosion resistance of stainless steel bipolar plates by the formation of thermally-induced Cr-nitride

Abstract

Cr-nitride layer is formed on the surface of Cr-electroplated stainless steel to use metallic bipolar plates of polymer electrolyte membrane fuel cell (PEMFC). The dense and continuous Cr-nitride layer is confirmed by scanning electron microscope (SEM) results. The corrosion resistance results in aggressive environments of PEMFC reveal that the corrosion current density of 0.5 mu A cm(-2) and 0.5 mu A cm(-2) are presented in anodic and cathodic environments of PEMFC, respectively. The highest protective efficiency of 99.9% is recorded in the cathodic condition. The dense Cr-nitride layer provides sufficient corrosion resistance. Moreover, the interfacial contact resistance (ICR) of Cr-nitride layer is significantly decreased up to 15 m Omega cm(-2) compared with pure stainless steel and the ICR is maintained after corrosion tests. This analysis indicates that the improvement is originating solely from dense Cr-nitride layer on the surface.