Formation of a protective TiN layer by liquid phase plasma electrolytic nitridation on Ti–6Al–4V bipolar plates for PEMFC

Abstract

The current work mainly investigates the corrosion resistance and conductivity of TiN layer on Ti–6Al–4V with liquid phase plasma electrolytic nitridation for PEMFC bipolar plate (BP). The X-ray diffraction (XRD) results show that TiN phase presents in the nitriding samples. The surface morphology analysis indicates that higher CH4NO2 concentration tends to form more compact structure. The potentiodynamic polarization test indicates that sample N-600 prepared by 600 g/L CH4NO2 concentration possesses the lowest corrosion current density of 0.57 μA cm−2 in the simulated PEMFC cathode potential (+0.6 VSCE), which completely satisfies the DOE 2020 technical targets. Meanwhile, sample N-600 also exhibits the highest corrosion resistance and stability in the potentiostatic polarization, electrochemical impedance spectroscopy (EIS) and high potential (+1.6 VSCE) polarization test. Interfacial contact resistance (ICR) results show that sample N-600 possesses the lowest ICR value of 6 ± 0.4 mΩ cm2, which fully meets the DOE 2020 requirements.