Electrochemistry of Titanium in NaCl ‐ KCl Mixtures and Influence of Dissolved Fluoride Ions

Transient electrochemical techniques show that in NaCl ‐ KCl melts the reduction of TiCl 4 occurs through a three‐step reaction, Ti(IV) ⇒ Ti(III) ⇒ Ti(II) ⇒ Ti. The diffusion coefficients of the electroactive species and the standard potentials, E 43 0 , E 32 0 , and E 20 0 , for the couples, Ti(IV)/Ti(III) Ti(III)/Ti(II) and Ti(II)/Ti were measured by chronopotentiometry and cyclic voltammetry. The influence of the melt composition has been examined. The addition of fluoride ions, a common ligand for titanium ions, induces a negative shift of about 1 V in the potentials, E 43 0 and E 32 0 . It results in a decreasing influence of the disproportionation process 3 Ti ( II ) ⇒ Ti + 2 Ti ( III ) which depends on the F/Ti ratio and on the concentration of titanium ions.