Corrosion Behavior and Interfacial Contact Resistance of TiN Coated Type 316L Stainless Steel as Bipolar Plate for Proton Exchange Membrane Fuel Cell

AISI 316L stainless steel (SS) due to its superior features such as availability, low material and production costs and good corrosion resistance, strength, and weldability can be a suitable choice for bipolar plate material in proton exchange membrane fuel cells (PEMFCs). However, there are two important problems with using this type of steel as a bipolar plate: low corrosion resistance and high interfacial contact resistance (ICR) in PEMFC conditions. For solving these problems, investigations and development of different coatings and/or surface treatments are inevitable. In this paper, corrosion behavior and ICR of 1 mm-thick 316L metallic bipolar plates coated with TiN at three different thicknesses (1, 2, and 3 μm) using a physical vapor deposition (PVD) technique are investigated. The potentiodynamic polarization and electrochemical impedance tests are conducted at 80 °C in pH3 H2SO4+2 ppm HF solution purged with either O2 or H2, and the potentiostatic corrosion tests are performed under both simulated cathode and anode conditions. The TiN coated 316L plates exhibit improved corrosion resistance and retard the corrosion. The promising results in about all electrochemical tests is related to 3 μm-TiN coated specimens. The TiN coated 316L SS exhibits much lower ICR than uncoated 316L SS