Comparison of corrosion behavior between coarse grained and nanocrystalline NiFe alloys in chloride solutions and proton exchange membrane fuel cell environment by EIS, XPS and Raman spectra techniques

The corrosion resistance of coarse grained and nanocrystalline NiFe alloys in chloride solutions and proton exchange membrane fuel cell environment was investigated. The nanocrystalline NiFe alloys were obtained by electrodeposition, while coarse grained NiFe alloys were obtained by annealing. The results from electrochemical tests showed that coarse grained NiFe alloys had higher corrosion resistance than nanocrystalline samples in NaCl solution due to more compact passive films formed on the surface of coarse grained NiFe alloys. In addition, Raman spectra test showed that many nanocrystalline boundaries in electrodeposited NiFe alloys promoted the diffusion of nickel, which resulted in the formation of more nickel oxides and nickel hydroxides. However, the electrochemical study showed that coarse grained sample had lower corrosion resistance than nanocrystalline one in a typical proton exchange membrane fuel cell environment. The present study showed that nanocrystalline NiFe alloys were more suitable for the bipolar plates in proton exchange membrane fuel cell environment.