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چکیده
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High electrical conductivity and excellent corrosion resistance are essential requirements for metallic bipolar plates (BPPs). A new duplex surface modification, including plasma nitriding and physical vapor deposition (PVD) processes, was performed to apply a nanometric Cr/CrN multilayer coating on plasma-nitrided 316L stainless steel. The performance of the plasma nitrided, PVD-coated and combined plasma nitriding/PVD-treated SS316L BPPs were evaluated using phase and morphological characterizations, surface wettability measurement, interfacial contact resistance (ICR) and electrochemical investigations in a simulated PEMFC cathode environment at ambient temperature and 75 °C, including potentiodynamic and potentiostatic polarization tests, as well as electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis. The microstructural characterizations confirmed the formation of homogenous and compact coatings with a nanometric multilayer structure. Electrochemical tests revealed that the nanometric Cr/CrN multilayer coating dramatically increased the corrosion resistance of the uncoated SS316L BPP by 100 orders of magnitude at simulated PEMFC cathode condition, with an excellent dissolution current density of 1.1×10-7 A cm-2. The ICR of the uncoated SS316L BPP was decreased from 186 mΩ cm2 to 10.2 mΩ cm2 by deposition of nanometric Cr/CrN multilayer coating. Moreover, post-analysis confirmed that the nanometric Cr/CrN multilayer PVD-coated SS316L can be a promising candidate for BPP application.
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