Effect of potential on the early stage of nucleation and growth during aluminum electrocrystallization from molten salt (AlCl3–NaCl–KCl)

Electrodeposition of aluminum onto graphite from a molten electrolyte containing AlCl3–NaCl–KCl was studied by the method of chronoamperometery. In the early stage of the deposition and at low cathodic potentials two-dimensional (2D) nucleation and growth proceeding through instantaneous and a multitude of progressive steps followed the initial double layer charging. The processes are manifested as peaks on a decaying chronoamperogram. Non-linear fitting methods were applied to obtain the kinetic parameters in the light of Bewick, Fleischmann and Thirsk (BFT) theory. Under more cathodic potentials, transition from 2D to three-dimensional (3D) processes have been observed as manifested in the form of plateau on decaying chronoamperograms. The kinetic parameters associated with 3D progressive growth mechanism was obtained as above but using the Armstrong, Fleischmann and Thirsk (AFT) model.