Mitigating Transient Potential Induced Dissolution on Multilayered C/Ti Nanoscale Coating

Abstract

Cathodic transient potentials (CTPs) originate from the start-up/shut-down stages of proton exchange membrane fuel cells (PEMFCs) not only accelerate the corrosion of the metal bipolar plates (BPs) but also degrade their interfacial contact resistance (ICR). Therefore, developing an electrically conductive and corrosion-resistant coating is essential. Herein, multilayered C/Ti nanoscale coating is prepared on SS316L (C/Ti/SS) to mitigate the dissolution induced by CTPs. Results show that C/Ti/SS achieves highly prominent ICR of 1.59 mΩ·cm² and corrosion rate of 2×10^-8 A/cm², remarkably better than the targets of 10 mΩ·cm² and 1×10^-6 A/cm², respectively. Long-term cyclic polarization test confirm the high stability of C/Ti/SS which offer effective protection for CTPs up to 1.5 V. Analysis of nanoscale coating microstructure and composition suggests that the significantly enhanced corrosion resistance is attributed to the diffusional interfaces optimizes the potential distribution cross the coating and the nanoscale Ti sandwiched between nanoscale C layers improves the transpassive potential of C/Ti/SS. Also, insight into the electron energy bandgap and its bending implies that a coating with high transpassive potential is profitable to limit the dissolution induced by CTPs and thus promote its application on metal BPs used in PEMFCs.

Keywords: multilayered C/Ti nanoscale coating, cathodic transient potentials, interfacial contact resistance, Corrosion resistance, metal bipolar plates, proton exchange membrane fuel cells