Characterization of the performance of Ti doped α-C/α-C multilayer coating on SS316L as bipolar plates for PEMFC

Abstract

In order to improve the corrosion resistance and conductivity of 316L stainless steel (SS316L) in the PEMFC (proton exchange membrane fuel cells) environment, DC-balanced magnetron sputtering was used to deposit Ti doped α-C/α-C multilayer coating on SS316L. The influence of coating structure on its micromorphology and phase composition is characterized, and the coating corrosion and conductivity were further explored. Notably, the investigation reveals that multi-layer structure can inhibit the growth of columnar crystal structure and refine the coating surface, which gradually decreased the coating porosity of from 4.54 % (1 layer) to 0.21 % (4 layers), and the passivation current density decreases to 0.22 μA/cm2 at 0.6 V, remarkably better than the targets. In addition, the introduction of Ti-doped α-C layer further promoted the sp2 hybridization of the coating, its interfacial contact resistance (ICR) value gradually decreased from 5.28 mΩ·cm2 (1 layer) to 2.28 mΩ·cm2 (4 layers) under 1.4 MPa. Therefore, the multilayer composite structure coating significantly enhances the conductivity and corrosion resistance of the SS316L bipolar plate, are more practically applied for commercialization of PEMFC technology.