Electrochemical properties of TiN coatings on 316L stainless steel separator for polymer electrolyte membrane fuel cell

TiN films for metallic bipolar plates were synthesized by closed-field unbalanced magnetron sputtering (CFUBM) and the properties were controlled by adjusting the N2 partial pressure. The corrosion behaviors of TiN films were investigated by potentiodynamic tests and electrochemical impedance spectroscopy (EIS) measurements under the condition of an aerated 1 M H2SO4 + 2 ppm HF solution at 70 °C with a constant potential of 600 mVSCE. The results revealed that the variation of N2 pressure had an influence on the corrosion resistance of TiN coating. N2 partial pressure of 0.4 mTorr showed good corrosion resistance with the lowest corrosion current density and the highest charge transfer resistance due to the low porosity.