The study of Ni-based nano-crystalline and amorphous alloy coatings on AISI 304 stainless steel for PEM fuel cell bipolar plate application

Bipolar plates are one of the most important parts of proton exchange membrane fuel cells (PEMFCs) which their performance has appreciable effect on cell operation. In this study, Ni-Mo and Ni-Mo-P alloy coatings were electrodeposited on AISI 304 stainless steel specimens as metallic bipolar plates in order to improve corrosion resistance, hydrophobicity and electrical conductivity of the specimens. Scanning electron microscopy (SEM) micrographs showed that the prepared coatings were uniform and compact. Moreover, X-ray diffraction (XRD) analysis indicated that the coatings were composed of a solid solution where Ni-Mo and Ni-Mo-P coatings had nanocrystalline and amorphous structures, respectively. The potentiodynamic and potentiostatic polarization tests in a simulated PEMFC cathode environment showed that corrosion resistance of the coated specimens was considerably improved compared to that of the bare one. Furthermore, interfacial contact resistance (ICR) before and after potentiostatic test was significantly decreased by applying Ni-Mo and Ni-Mo-P coatings, where ICR values of the as-deposited bipolar plates were reduced by approximately eight times in comparison to that of the bare 304 stainless steel at typical compaction force of 220 N/cm2. Therefore, the investigated Ni-Mo and Ni-Mo-P coatings would be potentially good candidates as metallic bipolar plates in PEMFC. Moreover, Ni-Mo and Ni-Mo-P alloy coatings showed higher surface hydrophobicity than the bare 304 stainless steel, which is advantageous for water management and also for corrosion resistance improvement.