Effect of plasma electrolytic nitriding on the corrosion behavior and interfacial contact resistance of titanium in the cathode environment of proton-exchange membrane fuel cells.

Abstract In this study, plasma electrolytic nitriding technology and an annealing treatment are used to modify titanium bipolar plates. Subsequently, the surface topography, corrosion resistance, and interfacial contact resistance of the nitrided samples are characterized. The results show that the nitrided layer consists of porous volcano-like micro-nano structure surface layer and the dense inner layer. Compared to the blank sample (87.9°±1.7°), the contact angle between the nitrided samples with annealing and deionized water significantly increases (104.7°±1.4° (nitrided for 15 min), 114.3 ± 3.0° (nitrided for 30 min)). The results of the electrochemical and atomic force microscopy analysis indicate that the nitrided samples with annealing have good corrosion resistance. The corrosion potential and corrosion current density of the nitrided samples with annealing are −0.016 V (Ag/AgCl) and 0.275 μA cm−2 (nitrided for 15 min) and 0.04 V (Ag/AgCl) and 0.195 μA cm−2 (nitrided for 30 min), respectively, which satisfy the requirement of DOE 2020 target (<1 μA cm−2). After potentiostatic polarization at 600 mV (SCE) in the simulated environment, the contact resistance of the samples remains very low (6.47 mΩ cm2 (nitrided for 15 min) and 3.91 mΩ cm2 (nitrided for 30 min)) and also satisfies the requirement of the DOE (≤10 mΩ cm2). Highlights • Plasma electrolytic nitriding technique was used to modify titanium bipolar plates. • Nitriding and annealing treatment improved significantly the corrosion resistance. • ICR of nitrided samples with annealing met the goal of DOE. [ABSTRACT FROM AUTHOR]