Preparation and properties of nitride multilayer coating modified stainless steel as bipolar plates for proton exchange membrane fuel cells

Nitride multilayer coating is prepared on 316L stainless steel (SS) by employing multi-arc ion planting to enhance the corrosion resistance, interfacial electrical conductivity, and hydrophobicity. The electrochemical results show that the coating can effectively inhibit the interface reactions. The i_corr of the coated 316L SS was 0.04 μA cm⁻², which was significantly lower than that of the substrate (54.7 μA cm⁻²). The protection efficiency (P_i) of the multilayer nitride coating was 99.93%. After 9 hours of PP, the current density of the coated 316L SS stabilized at 0.085 μA cm⁻². The typical ICR value of the coated 316L SS slightly increased from 8.6 mΩ cm² to 12.6 mΩ cm². The XPS results demonstrated that the significantly increased ICRs (114.7–200.4 mΩ cm²) of the 316L SS substrate were mainly attributed to the increased proportion of Cr oxide, while the oxide content of the coating was still relatively small. The change in surface morphology and current transient events are further discussed.