C/CrN multilayer coating for polymer electrolyte membrane fuel cell metallic bipolar plates

The two most important issues that plague wider use of stainless steel bipolar plates in polymer electrolyte membrane fuel cells (PEMFCs) are insufficient corrosion resistance and surface conductivity. In this study, C/CrN multilayer coatings are deposited on 316L stainless steel samples by close-field unbalanced magnetron sputtering ion plating. SEM shows that the C/CrN coatings are dense, continuous, and composing of carbon granules on the surface. Raman spectroscopy reveals an amorphous structure with a large sp(2) constituent. The corrosion resistance and interfacial contact resistance (ICR) are investigated systematically. A superior ICR in the range of 2.6-2.9 m Omega-cm(2) at a compaction force of 150 N/cm(2) is achieved and it is even better than that of graphite. The deposited film possesses high chemical inertness thereby significantly enhancing the corrosion resistance of the coated SS316L. A thickness of 800 nm is sufficient to protect against corrosion. C/CrN multilayer coatings are beneficial in that it can lead to a faster PVD deposition process and lower material cost, while permitting a superior performance in terms of surface conductivity and corrosion resistance. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.