Long-term polarization accelerated degradation of nano-thin C/Ti coated SS316L bipolar plates used in polymer electrolyte membrane fuel cells

Dynamic potentials of polymer electrolyte membrane fuel cells (PEMFCs) lead to the corrosion of metal bipolar plates and significantly increase their interfacial contact resistance (ICR). Herein, two nano-thin C/Ti coatings with different thicknesses are prepared on SS316L (C/Ti/SS) and examined under three types of polarization potential modes. The C 100 Ti 60 coating has improved corrosion resistance than C 20 Ti 140 coating. The C 100 Ti 60 coating exhibits a low ICR of 2.67 mΩ cm 2 and a small corrosion rate of 1.47 μA/cm 2 , highlighting the high electrical conductivity and corrosion resistance. Moreover, C 100 Ti 60 /SS achieves a slight degradation of ICR after polarization at 0.67 V and cyclic polarization between 0.43 and 0.73 V. However, the high potential of 1.43 V induces severe delamination of C layer, resulting in a remarkable increase of ICR. Analysis suggests that the Ti layer improves the oxidation resistance and the C layer could provide effective protection when the potential is below 1.13 V. • Two nano-thin C/Ti coatings with different thicknesses are prepared on SS316L. • Highly corrosion resistant and electrical conductive C 100 Ti 60 /SS is achieved. • Evolution of ICRs of C 100 Ti 60 /SS under three polarization modes are studied. • Anodic dissolution processes of C 100 Ti 60 /SS at different potentials are analyzed. • Correlation between ICR and negative current during cyclic polarization is discussed.