Abstract:In the present study, ZrC nanocrystalline coating was synthesized on Ti-6A1-4V alloy as bipolar plates for PEMFC by a double glow discharge plasma technique. The microstructure of as-prepared ZrC coating was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Electrochemical measurements were carried out on a CHI604D electrochemical workstation in the simulated PEMFC anodic and cathodic environments. The hydrophilicity and interfacial contact resistance of the ZrC nanocrystalline coating were also evaluated. The microstructure of as-prepared ZrC coating consists of deposited layer and diffusion layer. The 10 μm thick deposited layer shows a dense columnar microstructure, composed of equiaxed grains with an average grain size of ~12 nm, whereas the 4 μm thick diffusion layer with the gradient distribution of alloying elements offers a smooth transition of mechanical properties, which is beneficial to improve the adhesion strength of the ZrC coating on the Ti-6A1-4V substrate. The Ecorr of the as-deposited ZrC nanocrystalline coating is obviously higher than that of Ti-6A1-4V alloy in a simuiated PEMFC environment. At applied cathode ( 0.6 V) potential for PEMFC, ZrC nanocrystalline coating is in passive region, and the passive current density is four orders of magnitude lower than that of Ti-6A1-4V alloy. At applied anode (-0.1 V) potentia, ZrC nanocrystalline coating exhibits the characteristic of cathodic protection. The results of OCP and EIS showed that the higher the temperature, the worse the corrosion resistance of bipolar plates. And the temperature corrosion susceptibility of ZrC nanocrystalline coating is obviously lower than Ti-6A1-4V alloy. Moreover, ZrC nanocrystalline coating can effectively improve conductivity and hydrophobic nature of Ti-6A1-4V alloy bipolar plate.