Corrosion resistance and electrical conductivity of Ta-modified Titanium bipolar plates for PEMFC

Titanium alloy bipolar plates hold significant promise for proton exchange membrane fuel cells (PEMFC) due to their high specific strength, excellent machinability and low density. However, the surface oxide film readily reacts with fluoride ions (F⁻) in service environments, forming porous, layered fluorotitanium compounds that compromise service life and stability. To overcome these limitations, this study utilised magnetron sputtering to deposit a 1 μm-thick tantalum (Ta) coating on TA1 titanium alloy substrates. The microstructure, corrosion resistance and electrical conductivity of the Ta-coated samples were systematically investigated and the mechanisms underlying their enhanced performance were analysed. Results showed that the Ta coating featured a dense, uniform microstructure with strong adhesion to the substrate and no detectable metallurgical defects. A gradient distribution of elements within the diffusion layer further strengthened the coating-substrate interface. Moreover, the formation of a Ta₂O₅ passivation film on the coating surface effectively inhibited fluoride-induced corrosion, reducing the contact resistance from 69.9 to 31.7 mΩ·cm². These findings provide critical theoretical insights and practical guidance for enhancing the corrosion resistance and electrical conductivity of titanium alloy bipolar plates, paving the way for their broader application in PEMFC systems.