Influence of Cr-C film composition on electrical and corrosion properties of 316L stainless steel as bipolar plates for PEMFCs

Stainless steel (SS) has received much attention in recent years as an alternative material for bipolar plates (BPPs) in proton exchange membrane fuel cells (PEMFCs). However, stainless steel BPPs are still required to combat corrosion in the acid environment without forming oxidants, passive layers and metal ions. In this study, multilayered chromium carbon (Cr-C) film is deposited on SS316L sheet as BPPs using closed field unbalanced magnetron sputter ion plating (CFUBMSIP). Five films with different composition are deposited and the influence of chromium content adjusted by sputtering current is characterized by X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Interfacial contact resistance (ICR) between coated SS316L sheets and gas diffusion layer (GDL) is measured. Potentiodynamic and potentiostatic tests are conducted to evaluate the corrosion resistance of the coated samples. Experimental results show that Cr-C film with content of Cr0.75C5 presents the optimal performance, i.e. the interfacial contact resistance(ICR) reduces to 1.4 m Omega cm(2) under a compaction pressure of 1.4 MPa, and the corrosion current density reaches 1.046 mu A cm(-2) in the PEMFCs cathodic environment (0.5 M H2SO4 + 5 ppm HF solution at 70 degrees C, 0.6 V vs. SCE). The performance variation of five films can be preliminarily explained by the crystallographic structure and chemical composition analysis. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.