The chemical resistance of Tantalum to aqueous chemicals is the highest among metals. In the ambient atmosphere, Tantalum forms a very dense Ta2O5 layer which passivates the base material against corrosion. Tantalum has proven itself to be totally inert as a wet electrical contact (metal clip) in electrochemical cells. It is a decent conductor of electricity, while not participating in electrochemical reactions. Therefore, the sample of electrochemically active material can be electrically connected via Tantalum lead and such connection may be immersed in the electrolyte. The current occurring from the Tantalum contact itself (site reactions) is negligible and does not contribute to the measured current at the working electrode.
Like glass, Tantalum only suffers from hydrofluoric acid and strong hot alkali solutions. In those applications, Copper contact is the obvious choice.