Role of oxide layer on corrosion resistance and surface conductivity of titanium bipolar plates for proton exchange membrane fuel cell

Heat-assisted forming (either hot stamping or multi-step forming with intermediate annealing) has been demonstrated as an effective novel forming process of titanium bipolar plate (Ti-BPP) with fine flow channels and high geometrical accuracy, where an oxide layer can be introduced to Ti-BPPs due to thermal oxidation. Although low-cost coating (e.g., amorphous carbon coating) is normally applied to Ti-BPPs in order to increase their corrosion resistance and surface conductivity, the impact and mechanism of oxide layer on the corrosion resistance and surface conductivity of coated Ti-BPPs remain unclear. This work finds that the oxide layer introduced by thermal oxidation enhances the corrosion resistance of coated Ti-BPPs (cathodic corrosion current density decreased from 1.54 to 0.54 μA/cm2) without reducing surface conductivity. The oxide layer thickens from