Corrosion characteristics of SS316L as bipolar plate material in PEMFC cathode environments with different acidities

The corrosion characteristics of SS316L in simulated proton exchange membrane fuel cell (PEMFC) environments with a wide range of H2SO4 concentrations have been systematically studied. Electrochemical methods, both potentiodynamic and potentiostatic, are employed to determine the corrosion parameters and the results show that corrosion resistance decreases with increasing H2SO4 concentrations. Scanning electron microscope (SEM) is used to examine the surface morphology of the specimens after potentiostatic polarized in simulated PEMFC cathode environments and the results indicate that local corrosion occurs under all the conditions studied and local corrosion is more severe with higher H2SO4 concentrations. Auger electron spectroscopy (AES) analysis is used to identify the composition and the depth profile of the passive film formed on the SS316L surface and the results show that the thickness of passive film decreases with increasing H2SO4 concentrations. Interfacial contact resistances (ICR) between SS316L polarized and carbon paper are measured and the results show that ICR decreases with increasing H2SO4 concentrations. The corrosion mechanisms of SS316L in PEMFC cathode environments are analysed and discussions on choosing simulated PEMFC cathode corrosion environments for accelerated tests are also provided.