Nanometric CrN/CrAlN and CrN/ZrN multilayer physical vapor deposited coatings on 316L stainless steel as bipolar plate for proton exchange membrane fuel cells

Abstract

Nanometric CrN/ZrN and CrN/CrAlN multilayer coatings were deposited on 316L stainless steel as metallic bipolar plates (BPs) for proton exchange membrane fuel cells (PEMFCs) by the cathodic arc evaporation-physical vapor deposition technique. The coatings were evaluated using X-ray diffraction, field emission scanning electron microscopy, surface roughness determination, and water droplet contact angle measurement. In order to study the electrochemical behavior of the coatings, potentiodynamic polarization and electrochemical impedance spectroscopy examinations were conducted at the simulated cathodic PEMFC media (0.5 M H2SO4 purging O2, 70°C). Also, the interfacial contact resistance (ICR) of the coated and uncoated 316L BPs was evaluated in different compaction forces before and after the potentiostatic polarization test. The current density at 0.644 V vs. Ag/AgCl of 0.16 and 0.76 μA cm−2 was recorded for CrN/ZrN and CrN/CrAlN, respectively. Moreover, it was found that after the potentiostatic polarization tests, the ICR values of the 316L BPs were decreased from 276 to 8.3 and 9.4 mΩ cm2 by the deposition of the CrN/ZrN and CrN/CrAlN coatings, respectively. The enhancement in the ICR and corrosion behavior of both CrN/ZrN and CrN/CrAlN multilayer coatings indicated that these coatings can be potentially suitable for PEMFCs application, according to the United States Department of Energy's targets.