Nitrogen incorporation window for optimizing TiN-coated SS316L bipolar plates for PEM fuel cell applications

Titanium nitride (TiN) coatings were deposited on SS316L metallic bipolar plates using advanced cathodic arc physical vapor deposition with nitrogen flow rates ranging from 11 to 48 sccm to investigate the influence of nitrogen incorporation on the performance of proton exchange membrane fuel cell (PEMFC) bipolar plates. The effects of varying nitrogen flow rates on corrosion behaviour, interfacial contact resistance, surface wettability, and electrochemical stability were evaluated under simulated PEMFC cathode conditions. The coating deposited at 28 sccm, corresponding to a near-stoichiometric TiN coating, exhibited the lowest corrosion current density of 0.245 μA/cm 2 , the highest polarization resistance of 15.031 Ω cm 2 , and maintained an interfacial contact resistance below 10 mΩ cm 2 at a contact pressure of 0.72 ± 0.22 MPa. A lower nitrogen flow rate resulted in inferior corrosion resistance, whereas increasing the nitrogen flow rate beyond 28 sccm reduced the contact pressure required to achieve the target interfacial contact resistance but increased the corrosion current density. These findings indicate that a nitrogen flow rate of 28 sccm provided the most favourable balance between corrosion resistance and interfacial contact performance among the investigated coatings and highlight the influence of nitrogen incorporation on coating characteristics and electrochemical and electrical performance.