Nanostructured multilayer Cr/CrN coatings on 316L stainless steel for proton exchange membrane fuel cell bipolar plates

Nowadays, hybrid surface modification approaches offer tailored solutions for improving the corrosion resistance and electrical conductivity of the bipolar plates (BPPs) in proton exchange membrane fuel cells (PEMFCs). In the present study, a combination of plasma nitriding and physical vapor deposition (PVD) processes was used to apply a nanometric Cr/CrN multilayer coating onto 316L stainless steel (SS316L) bipolar plates. The performance of the resulting plasma nitrided, PVD-coated, and combined plasma nitriding/PVD-coated SS316L BPPs was examined by phase and morphological characterizations, surface wettability measurements, interfacial contact resistance (ICR), and electrochemical investigations. Potentiodynamic and potentiostatic polarization evaluations, electrochemical impedance spectroscopy (EIS) and Mott-Schottky asessments were conducted on the coated samples in a simulated PEMFC cathode environment at temperatures of 25 degrees C and 75 degrees C. Results indicated that the Cr/CrN multilayer coating deposited on the plasma-nitrided 316L BPP exhibited a remarkable 100-fold improvement in corrosion resistance compared to the uncoated substrate. Also, the combination of nitriding and PVD resulted in a significant reduction of the ICR from 186 m Omega cm2 for the uncoated SS316L to 10.2 m Omega cm2 for the coated sample. Multilayer coatings based on the combination of plasma nitriding and PVD treatment can identified as promise candidates for BPP applications.