Corrosion and interfacial contact resistance of 316L stainless steel coated with magnetron sputtered ZrN and TiN in the simulated cathodic environment of a proton-exchange membrane fuel cell

Abstract

To improve the corrosion resistance and electrical conductivity of 316L stainless steel used as a bipolar plate, TiN and ZrN coatings are deposited on the surface through magnetron sputtering in this study. Subsequently, the surface topography, composition, corrosion resistance, and interfacial contact resistance of the coated samples are characterized. The results show that the TiN and ZrN coating can significantly enhance the corrosion resistance of the 316L stainless steel. The corrosion current density of the coated 316L stainless steel with TiN and ZrN in the simulated cathodic environment of a proton-exchange membrane fuel cell (PEMFC) is 0.099 μA/cm2 and 0.209 μA/cm2, respectively, which meets the U.S. DOE 2020 target (<1 μA·cm−2). The EIS and polarization curves show that the TiN coating has better corrosion resistance than that of the ZrN coating. Moreover, the contact angle results indicate that TiN and ZrN can also improve the hydrophobicity of the stainless steel. The interfacial contact resistance between the TiN-coated sample and carbon paper before and after polarization is the smallest, which satisfies the U.S. DOE requirement (≤10 mΩ·cm2).