A ZrN nanocrystalline coating for polymer electrolyte membrane fuel cell metallic bipolar plates prepared by reactive sputter deposition

Abstract

To improve the surface performance and durability of 316L stainless steel (SS) used in polymer electrolyte membrane fuel cell (PEMFC) environments, a ZrN coating with an average grain size of ∼15 nm, was deposited by reactive sputter-deposition using a double glow discharge plasma technique. The corrosion behavior of the as-deposited coating was examined and compared to uncoated 316L SS in simulated PEMFC environments (i.e., 0.5 M H₂SO₄ + 2 ppm HF solution) by potentiodynamic and potentiostatic polarizations along with electrochemical impedance spectroscopy (EIS). The results showed that the corrosion resistance of the ZrN-coated 316L SS was significantly higher than that of uncoated material. Additionally, in comparison with uncoated 316L SS, the interfacial contact resistance (ICR) between the ZrN-coated 316L SS and the simulated gas diffusion layer (i.e., conductive carbon paper) was reduced by two orders of magnitude and remained mostly unchanged after potentiostatic polarization for 5 h. Furthermore, the average contact angle with water for the ZrN coated 316L SS (84.9°) was higher than that of uncoated material (64.4°), indicating that the ZrN-coated 316L SS is more hydrophobic.