— Prof. S. Ramanathan, et al.
In our recent investigation, we have identified the detailed mechanism of anodic dissolution of two very inert valve metals. viz. Ta and Nb in hydrofluoric (HF) acid using in situ electrochemical impedance spectroscopic (EIS) characterization of the dissolution process and analysis of the data. HF is a very aggressive medium with very limited scope for insitu characterization. Ta and Nb instantaneously form passivating layers in almost all media and thus ex situ characterization has questionable validity in describing their dissolution in HF. Mechanistic analysis of EIS data enables one to obtain a clear understanding of these difficult systems.
On the Anodic Dissolution of Tantalum and Niobium in Hydrofluoric Acid, P.M. Ranjith, Tirumala Rao Mandula, Sanjeev Sapra, Ian Ivar Suni, Ramanathan Srinivasan, J. Electrochem. Soc. 165 (3) (2018) C258-269 (Link)