Effect of carbon doping on corrosion resistance and conductivity of CrMoN-coated 316L stainless steel bipolar plates

CrMoCN coatings with different carbon contents are prepared on 316L stainless steel substrates by closed-field unbalanced magnetron sputtering. The microstructure, phase composition, bonding state, corrosion properties, interfacial conductivity, and hydrophobicity of the coatings are investigated. The structural analysis shows that the nitride coating gradually changes to the coexistence of nitride phase, carbide phase, and amorphous carbon with increasing carbon content. As the phase structure transition, the CrMoCN-14 coating possesses the lowest corrosion current density of 6.28 × 10−8 A cm−2 after potentiodynamic polarization in the simulated cathodic environment. The electrochemical impedance spectroscopy also proved that the CrMoCN-14 sample has the best chemical stability. Furthermore, the CrMoCN-14 coating has a very low interfacial contact resistance value of 7.54 mΩ cm2 compared to the SS316L substrate. The analysis results demonstrated that the CrMoCN coating has excellent anti-corrosion performance and interfacial conductivity and is a potential material for bipolar plates.