Effects of Mo content on the interfacial contact resistance and corrosion properties of CrN coatings on SS316L as bipolar plates in simulated PEMFCs environment

CrMoN films with different Mo contents are deposited on SS316L by closed filed unbalanced magnetron sputtering ion plating (CFUBMSIP) to investigate corrosion resistance and electrical conductivity. The sputtering current of Mo target was altered to obtain various Mo contents. The result of SEM confirms that CrMoN coatings have a dense and uniform microstructure. X-ray diffraction (XRD) result shows that CrMoN coated samples have a preferred orientation of (111) direction. Interfacial contact resistance (ICR) between bipolar plate and gas diffusion layer (GDL) decreases with Mo incorporation, and CrMoN-4A coated sample has the lowest ICR value of 5.8 mΩ cm2 at 1.4 MPa. The result of potentiodynamic polarization test in the simulated PEMFCs environment shows that incorporation of Mo doped CrN coating can obviously improve the corrosion resistance of samples and CrMoN-4A has the highest corrosion potential which is 0.1341 V in simulated PEMFCs cathode environment. Electrochemical impedance spectroscopy (EIS) result indicates that the incorporation of Mo can improve better corrosion resistance, and CrMoN-4A has the highest corrosion resistance. The corrosion mechanism of coating also has been investigated.