Galvanic corrosion is powerful enough to degrade materials that are individually corrosion resistant. Metal oxidation at an anodic reaction site on the less noble metal is coupled to reduction reactions at a cathodic reaction site on the more noble metal. The oxygen reduction reaction (ORR) is a major controlling reaction for galvanic corrosion in atmospheric conditions.^1-2 Thus, inhibiting ORR rates is a chance to inhibit galvanic corrosion. We use Kohn-Sham density functional theory to predict dopants that best inhibit ORR rates on natively formed Ti oxides.

We created an amorphous TiO₂ surface model that both agrees with experimental XRD data and predicts an ORR overpotential in good agreement with experimental measurements (exp = 0.45 V, PBE = 0.5 V and HSE06+VASPsol = 0.43 V). By modeling the ORR intermediates adsorbed to metal dopants embedded into our model surface at their most favorable oxidation states, we successfully predicted dopants that have been experimentally verified to reduce ORR currents by up to 77%. PBE predicted overpotentials agree with those predicted by hybrid DFT (HSE06) with VASPsol continuum solvation. Further work studying the potential impact of oxygen vacancies will be discussed.

References

1. Mansfeld, F.; Parry, E. P., Galvanic Corrosion of Bare and Coated Al Alloys Coupled to Stainless Steel 304 or Ti-6Al-4V. Corros. Sci. 1973, 13, 605-621.

2. Zhou, X.; Luo, C.; Hashimoto, T.; Hughes, A. E.; Thompson, G. E., Study of Localized Corrosion in AA2024 Aluminium Alloy Using Electron Tomography. Corros. Sci. 2012, 58, 299-306.