An in-depth understanding of the solvation effect of methanol on the anisotropy of electrochemical corrosion of Ta

Although tantalum (Ta) has been studied experimentally for many years as an important anti-corrosion material, it remains a challenge to accurately predict its corrosion anisotropy theoretically. In this work, we proposed an ab initio model considering the solvation effect to investigate crystal orientation-dependent corrosion behavior of Ta. The changes in electron transfer number and energy of a tantalum atom during its dissolution from the surface in vacuum and explicit methanol molecules were studied, respectively. Based on the anodic dissolution activation energy considering solvation effect, the corrosion current densities of (200), (110) and (211) surfaces were calculated to be 3.39 × 10⁻⁸ A/cm², 2.24 × 10⁻¹¹ A/cm² and 2.95 × 10⁻¹¹ A/cm², respectively. The results are consistent with the variation trend of peak intensity in the XRD pattern. More importantly, the corrosion current density we predicted based on the percentage of these crystalline surfaces in the polycrystalline tantalum foil is 10^−7.25 A/cm², which is very close to the experimental value (8.70 × 10⁻⁸ A/cm²). Therefore, this result is capable of providing a theoretical basis for the electrochemical machining of Ta and a new idea for studying the anodic dissolution behavior of other metals or alloys in solution.