Preparation and electrochemical corrosion of Cr–C coatings by cathode plasma electrolytic deposition for stainless steel bipolar plate in PEMFC

Cr-C coatings were prepared on 316L stainless steel by cathode plasma electrolytic deposition (CPED). The effects of trivalent chromium salt concentration in the plating solution and deposition time on the microstructure and composition of Cr-C coatings were investigated by means of scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The corrosion resistance and surface conductivity of Cr-C coated specimens in the simulated proton exchange membrane fuel cell (PEMFC) anode and cathode environments (i.e., 0.5 mol L -1 H 2 SO 4 + 2 ppm HF solution bubbled with hydrogen gas or air at 80 °C) were characterized by potentiodynamic polarization, potentiostatic polarization and interfacial contact resistance (ICR). Increasing the chromium salt concentration and deposition time results in higher corrosion resistance for the Cr-C coatings in both environments, but slightly lower surface conductivity. The optimal Cr-C coating deposited under 60 g L -1 chromium salt condition for 60 min passivates spontaneously and displays the current density values approximately -0.03 and 0.3 μA cm -2 after the potentionstatic polarization at -0.1 and 0.6 V SCE for 5 h in the simulated PEMFC anode and cathode environments, respectively, and the ICR values lower than 6 mΩ cm 2 . It is deserved to improve the CPED process of Cr-C coating for stainless steel bipolar plate.