Electrochemical and electrical resistance behavior of cathodic arc PVD TiN, CrN, AlCrN, and AlTiN coatings in simulated proton exchange membrane fuel cell environment

Proton exchange membrane fuel cells (PEMFC) attracted significant attention to meet energy demands for future applications. Graphite bipolar plates are currently being used due to its high corrosion resistance and electrical conductivity, but for economic reasons, metallic bipolar plates are being considered as a cost-effective alternative. However, corrosion poses a serious challenge with the use of metallic bipolar plates. This study deals with the evaluation of the corrosion properties of TiN, CrN, AlTiN, and AlCrN coatings in PEMFC application. Electrochemical tests under anodic and cathodic conditions and interfacial contact resistance (ICR) test were used to investigate the electrochemical and electrical resistance properties. Results revealed that these coatings exhibit higher corrosion resistance as compared to 304 stainless steel in PEMFC environment. CrN and TiN coatings provided lower corrosion current density, higher durability, and lower ICR as compared to the ternary coatings. Corroded surface morphology revealed laths typed structure in the passive film of CrN and particle typed structure in that of TiN coating. However, AlCrN coating was found more durable than AlTiN coating under PEMFC environment. The incorporation of Al in TiN and CrN to form AlTiN and AlCrN coatings, respectively, affects the performance of the ternary coating in PEMFC environment despite the favorable influence it has on other properties of the coatings.