Investigation on the physical and electrochemical properties of typical Ni-based alloys used for the bipolar plates of proton exchange membrane fuel cells.

ABSTRACT

The phase, mechanical properties, corrosion resistance, hydrophobicity, and interface contact resistance of three typical Ni-based alloys (Hastelloy B, Hastelloy C-276, and Monel 400) and 304 stainless steels were experimentally studied to evaluate their service performances as bipolar plate materials of proton exchange membrane fuel cells. All four alloys exhibit single-phase face-centered cubic structure, high strength, good ductility, and high hardness. Hastelloy C-276 has the best ductility with an uniform elongation of 72.5% and highest hardness of 363.7 HV. Hastelloy B has the highest ultimate tensile strength of 913.6 MPa. The hydrophobicity of all four alloys is not good, although Monel 400 has the highest water contact angle of 84.2°. Hastelloy B, Hastelloy C-276, and 304 stainless steel exhibit unsatisfying corrosion resistance in a simulated acidic work environment of proton exchange membrane fuel cell (0.5 M H2SO4+2 ppm HF, 80 °C, H2) and high interface contact resistance. By contrast, Monel 400 demonstrates excellent corrosion resistance with a corrosion current density of 5.9 × 10-7 A cm-2 and a low interface contact resistance of 7.2 mΩ cm2 at 140 N/cm2. In terms of comprehensive performance, Monel 400 is the best uncoated material for the bipolar plates of proton exchange membrane fuel cells among typical Ni-based alloys.