Application of Electrochemical Techniques to the Study of the Diffusion of Aluminum Ions in Fused Salts, and of Solid‐State Interdiffusion in the System Al‐Ni

Abstract

The average diffusion coefficient of aluminum chlorocomplexes in alkali chloride melts was measured by chronopotentiometry. To avoid the disturbance due to the formation of dendritic deposition, an alloy forming nickel electrode was used. A careful examination of the chronopotentiograms indicates that the potential response of the electrode depends both on the diffusion of aluminum chlorocomplexes in the melt and on the interdiffusion of Al atoms in the metal phase. A model is presented for predicting the potentiale‐current relationship. Quantitative interpretation must include the variations of the activity coefficients of the electroactive species and the corrections due to the shift of the electrode interface during the electrolysis. Optimum conditions are indicated to obtain electrochemical responses controlled either by ionic diffusion or by metallic interdiffusion.