Corrosion resistance of Nb and NbTi alloy predicted by hydrogen evolution reaction models modified with Langmuir isotherm adsorption theory

Langmuir isotherm adsorption theory is involved in the conventional model to predict the corrosion resistance of Nb and Nb alloys. It is illustrated that the anti-corrosion properties of Nb are dependent on the crystal plane, pH values and solution temperature. Nb(110) plane with the lowest E_surf/ρ and the highest E_esc present the slower dissolution of Nb atoms, and then exhibits the best anti-corrosion performance. Alloying with Cr, Cu, Mo, Ti and Ta destroys the stability of Nb(110) plane and thus degrades the corrosion resistance performances. Moreover, the anti-corrosion performance is improved with increasing pH values because of the decreasing coverage of H⁺ ions. The escape rate of Nb atoms will be accelerated at the elevating temperature, and thus the anti-corrosion performance be degraded. Therefore, an appropriate design of coating texture and solution environment could improve the anti-corrosion performances of bipolar plates.