This paper concerns the corrosion behaviors of CrN/Cr-SS316L (with artificial defects) in a simulated high-temperature polymer electrolyte membrane fuel cell (HT-PEFC) cathode environment and the effect of oxygen on its corrosion processes. The overall anti-corrosion performance of CrN/Cr-SS316L (with artificial defects) was evaluated using the potentiodynamic polarization method under the environment with either N-2 or O-2 purging atmosphere. Electrochemical impedance spectroscopy was used to clarify the mechanisms of the corrosion processes. Scanning electron microscopy was then carried out to investigate the morphological changes of coated specimens before and after corrosion tests under different gas purging atmospheres. The existence of O-2 is essential for the CrN/Cr coating with surface defects maintaining good corrosion resistance in an HT-PEFC and oxygen could initialize the selfhealing ability of CrN/Cr coating with defects in the hot phosphoric acid. On the basis of the experimental findings, the mechanisms of the influence of oxygen on the corrosion processes of the CrN/Cr-SS316L in the simulated cathodic environment of an HT-PEFC are ultimately proposed. (C) 2019 The Electrochemical Society.

Using an electrochemical cell that was specially-designed for HT-PEFC experimental requirements, we analyzed a CrN/Cr-coated SS316L using potentiodynamic, potentiostatic and free corrosion potential monitor tests in the simulated cathodic environment of an HT-PEFC. By purging different gases (nitrogen, oxygen) into the electrolyte, we also investigated the influence of oxygen on the corrosion resistance of the CrN/Cr coating in simulated cathodic HT-PEFC environments. Additionally, ex-situ characterizations using SEM+EDX and ICR were carried out to investigate the metallic surface, anti-corrosion properties and interfacial contact resistance of samples before and after corrosion tests were carried out. Cathodic operation conditions included relatively high potential and the presence of oxygen beneficial for CrN/Cr coating so as to provide sufficient corrosion resistance to the cathodic HT-PEFC environment. Therefore, the CrN/Cr coatings are promising for the application in the cathode side of HT-PEFCs.