Durability and degradation of CrMoN coated SS316L in simulated PEMFCs environment: High potential polarization and electrochemical impedance spectroscopy (EIS)

Abstract

The high potential on the cathode side originated from the start-up/shut-down processes is the one that cannot be ignored, which will accelerate degradation of the bipolar plates and increase the interfacial contact resistance (ICR) eventually degrade the performance of PEMFCs. Therefore, the coating with corrosion resistance and conductivity is in urgent need of development. CrMoN coating is deposited on SS316L by closed field unbalanced magnetron sputter ion plating (CFUMSIP) with an aim to improve corrosion resistance and conductivity of SS316L under PEMFCs at shut-up/shut-down stages. In terms of high potential polarization test, the corrosion current density and ICR values are found to increase as the applied potential increases. The electrochemical degradation of CrMoN coated SS316L is investigated by electrochemical impedance spectroscopy (EIS). After 40 days of immersion, the charge transfer resistance (Rct) of the CrMoN-4A coated SS316L is approximately 14 times greater than that of the uncoated SS316L and the ICR values are 11.2 mΩ cm2, indicating that the CrMoN-4A coating still has high corrosion resistance and well conductivity after long time immersion.