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Corrosion Behavior of Tantalum Coatings on Bipolar Plate Substrates for PEM Fuel

"Corrosion Behavior of Tantalum Coatings on Bipolar Plate Substrates for PEM Fuel Cells"


Figure 1.a shows the electrodynamic polarization curves of two Ta-coated samples under anodic condition at two different times. Both samples show corrosion current density Icorr well below the DOE target value (<1x10-6 Acm-2) with no active-passive transition zone. On the other hand, the results obtained from the EIS test samples obtained after a similar treatment (Figure 1b) showed high polarized sheet resistance, thus supporting the results obtained in the DC test.

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Figure 1 a) Potential kinetic polarization curves of Ta coatings under anodic condition. b) Nyquist plot of EIS data obtained from tantalum-coated samples at different times and the treatment solution exposed to electrolysis (anode: H2SO4 + 0.1 ppm HF (pH3) at 80°C, degassed with N2 purge; cathode : H2SO4 + 0.1 ppm HF (pH 3 at 80°C, degassed with air purge).


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Figure2 Cross section (a) and coating surface (b) SEM image of Ta coating

Figure 2 shows the cross-section and surface SEM images of the Ta coating. Results After corrosion testing of the Ta coating, it was confirmed that there was no change in the surface morphology of the layer thickness (30 μm). Furthermore, the increased ICR values of the Ta-coated probes may be attributed to the columnar morphology observed in these samples. The presence of Ta surface oxides was confirmed by EDX analysis after corrosion testing.