Bimetallic CuNi Alloy Coatings on SS304 Substrate for Bipolar Plates of Proton Exchange Membrane Fuel Cells

The corrosion of metallic bipolar plates deteriorates the productivity and life cycle of proton exchange membrane fuel cells (PEM-FCs). Thus, the development of a high-performance protective coating that does not compromise the conductivity is crucial. In this study, bimetallic CuNi alloy coatings were directly grown on SS304 specimens by using chemical vapor deposition. The deposition period was periodically changed from 1 to 3 h to produce CuNi alloy coatings with varying structural characteristics. The detailed characterization indicated that the fabricated CuNi alloy coatings were homogeneous, dense, and crack-free with a thickness range of 1-2 μm. Further, the corrosion-resistant performance of CuNi-coated SS304 specimens was investigated in a PEM-FC operating simulated environment, and the results indicated that CuNi coatings developed for 3 h demonstrated the strongest surface protective activity with the lowest corrosion current density (0.125 μA cm²) and highest impedance values (92567 Ω cm²) in both PEM-FC operating cathode and anode conditions. The deposition of CuNi alloy films significantly reduced the interfacial contact resistance (ICR), and the CuNi-3h coating achieved a low ICR of 5 mΩ cm² under a compaction force of 150 N cm^-2. Detailed electrochemical characterization confirmed that the CuNi alloy coating has significant potential for use as a protective coating for PEM-FC SS bipolar plates.