Corrosion resistant and conductive amorphous carbon/Ti coatings on stainless steel bipolar plates prepared by filtered cathodic vacuum arc system

Improving the electrical conductivity and corrosion resistance of metal bipolar plates is crucial for proton exchange membrane fuel cells (PEMFCs). In this study, protective coatings with titanium as the base layer and amorphous carbon as the top layer were deposited on 316L stainless steel using a filtered cathodic vacuum arc (FCVA) deposition system. The effect of bias voltage on the morphology, composition, corrosion resistance, and interfacial contact resistance (ICR) of the amorphous carbon coatings was systematically investigated, with the corrosion mechanisms and surface property changes after corrosion were analyzed. During potentiostatic polarization tests at 0.6V (vs. SCE) and 1.3V (vs. SHE) for 10 h, corrosion current densities for all coatings were below 1 $\times$ 10⁻⁷ A/cm² and 1.5 $\times$ 10⁻⁶ A/cm². Even after potentiostatic polarization at 1.6V (vs. SHE), the ICR before and after electrochemical corrosion remained as low as 4.26 Ω cm² and 3.81 Ω cm². The coatings demonstrated excellent corrosion resistance and low ICR. Additionally, the degradation mechanism of the coatings under high-potential corrosion conditions was examined.