High potential corrosion resistance and conductivity performance of C-doped TiO2 coatings used in bipolar plates

To enhance the long-term high potential corrosion resistance of metal bipolar plates, carbon doped TiO2 films were deposited on 316L stainless steel using reactive magnetron sputtering. The structure and surface morphology of the coatings were systematically controlled by adjusting the oxygen flow rate. The study investigates the structural transformation of TiO2 under varying oxygen flow rates, focusing on the principles of corrosion resistance and conductivity for applications in fuel cell bipolar plates. The coating exhibits different corrosion behaviors under various potentiostatic polarization potential. The C doped TiO2 film prepared at an oxygen flow rate of 30sccm demonstrated the lowest corrosion current density, exhibiting no significant corrosion after 5 h of potentiostatic polarization at +1.6V (vs. SHE), with a corrosion current density of 1.04 mu A/ cm2. The primary corrosion mechanisms observed were uniform corrosion and pitting corrosion. By optimizing the oxygen flow rate, conductive pathways comprising Ti2O3 and TiO phases were formed, significantly reducing the interfacial contact resistance. Notably, samples prepared at oxygen flow rated of 25 sccm and 30sccm achieved excellent interfacial contact resistance values of 2.46 mS2 cm2 and 2.78 mS2 cm2, respectively.