Electrochemical Evaluation of Niobium Corrosion Resistance in Simulated Anodic PEM Electrolyzer Environment
Andrea Kellenberger, Delia Andrada Duca, Nicolae Vaszilcsin, Corneliu Marius Crăciunescu
Abstract
As cost reduction of stack components in proton exchange membrane (PEM) electrolyzers is needed, less expensive materials coated with anti-corrosive layers replace the state-of-the-art bipolar plates manufactured from massive titanium. One of the metals used for this purpose is niobium. In this work, we investigate the corrosion resistance properties of pure metallic niobium in simulated PEM electrolyzer environment. A corrosion test protocol was developed, including electrochemical impedance spectroscopy measurements, potentiodynamic polarization up to an anodic potential of 2 V followed by an accelerated stress test at 2 V for 6 hours. All tests were performed in O 2 saturated acid solutions, at 90°C to simulate the conditions at the anode side of PEM electrolyzers. In addition, interfacial contact resistance (ICR) measurements and scanning electron microscopy (SEM) imaging were performed both before and after the accelerated stress test. The presence of O 2 extends the potential range of the passive region as compared to solution without O 2 and the temperature increase leads to lower passivation and corrosion current densities. The passive oxide layer formed at higher temperatures is thicker, more compact and shows higher polarization resistance.