<p>Stainless steels are alternative materials for graphite bipolar plates in proton exchange membrane (PEM) fuel cells. Plasma electrolytic nitriding (PEN) of stainless steel 316L samples was carried out in an aqueous solution of urea. Grazing incidence X-ray diffraction analysis revealed the presence of Fe₂N_0.94, iron oxide, and X-ray photoelectron spectroscopy results showed iron nitride, iron oxide, and chromium oxides on the PEN-modified 316L surface. The thickness of the modified layer is approximately 1.1 μm as determined with glow discharge optical emission spectroscopy. The PEN-modified surface exhibited a lower corrosion current density of 88 ± 15 µAcm⁻² and 57 ± 16 µAcm⁻² in the simulated anodic and cathodic environments, while bare samples showed a corrosion current density of 155 ± 31 µAcm⁻² and 156 ± 15 µAcm⁻² in respective environments. Electrochemical impedance spectroscopy at open circuit potential revealed that PEN-modified surface has more polarization resistance than bare samples, indicating improved corrosion resistance. However, the long-term potentiostatic studies for 8 h showed that PEN-modified samples have higher passive current densities of 17.7 µAcm⁻² and 4.2 µAcm⁻² in anodic and cathodic environments, whereas bare samples showed 1.4 µAcm⁻² and 0.6 µAcm⁻² in respective environments. The concentration of total dissolved metal ions after potentiostatic polarization is significantly reduced after PEN modification, where the PEN-modified samples showed only 2.37 mgL⁻¹ and 5.54 mgL⁻¹ in anodic and cathodic environments, while bare samples showed 16.99 mgL⁻¹ and 20.24 mgL⁻¹ in respective environments. Interfacial contact resistance (ICR) values for bare and PEN-modified 316L at a compaction load of 140 Ncm⁻² were 118.8 ± 4.6 mΩcm² and 26.8 ± 3.7 mΩcm², respectively.</p> Graphical Abstract <p></p>