Coated 316L stainless steel with CrxN film as bipolar plate for PEMFC prepared by pulsed bias arc ion plating

Three different kinds of Cr_xN films on 316L stainless steels were prepared by pulsed bias arc ion plating as bipolar plates for proton exchange membrane fuel cell (PEMFC). The interfacial contact resistance, corrosion resistance and surface energy of the bipolar plate samples were investigated. Among the three samples, the 316L stainless steel coated with Cr_0.49N_0.51 → Cr_0.43N_0.57 gradient film (sample 2) exhibited the best-integrated performance. The contact resistance between sample 2 and Toray carbon paper was 6.9–10.0 mΩ cm² under 0.8–1.2 MPa. The bipolar plate sample also showed improved corrosion resistance in simulated PEMFC environments. Either in the reduction environment or in the oxidation environment 25 °C and 70 °C, the corrosion current densities of sample 2 were about one to two orders of magnitude lower than those of the base metal. In addition, the open circuit corrosion potential of sample 2 was also the highest in 0.5 M H₂SO₄ + 5 ppm F⁻ solution at 25 °C. The treated bipolar plate had high surface energy; and the contact angle of sample 2 with water was about 90°, which is beneficial for water management in fuel cell.