Growth of Cr-Nitrides on commercial Ni–Cr and Fe–Cr base alloys to protect PEMFC bipolar plates

• Published in: International journal of hydrogen energy 2007-11, Vol.32 (16), p.3778-3788
• Main Authors: Brady, M.P., Wang, H., Yang, B., Turner, J.A., Bordignon, M., Molins, R., Abd Elhamid, M., Lipp, L., Walker, L.R.
• Format: Article
• Language: English
• Subjects: 30 DIRECT ENERGY CONVERSION; ADVANCED PROPULSION SYSTEMS; Applied sciences; Bipolar plate; Condensed Matter; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cell; Fuel cells; Materials Science; Nitridation; Nitride; nitrides; Oxidation; Physics
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2006.08.044

Nitridation of Cr-bearing alloys can yield low interfacial contact resistance (ICR), electrically conductive and corrosion-resistant CrN or Cr 2N base surfaces of interest for a range of electrochemical devices, including fuel cells, batteries, and sensors. This paper presents results of exploratory studies of the nitridation of commercially available, high Cr (30–35 wt%) Ni–Cr alloys and a ferritic high Cr (29 wt%) stainless steel for proton exchange membrane fuel cell (PEMFC) bipolar plates. A high degree of corrosion resistance in sulfuric acid solutions designed to simulate bipolar plate conditions and low ICR values were achieved. Oxygen impurities in the nitriding environment were observed to play a significant role in the nitrided surface structures that formed, with detrimental effects for the Ni–Cr base alloys, but beneficial effects for the stainless steel alloy. Positive results from single-cell fuel cell testing are also presented.