Electrochemical Deposition of Aluminum from NaCl ‐ AlCl3 Melts

Electrochemical deposition of aluminum from melts saturated with onto a glassy carbon electrode at 175°C has been studied by voltammetry, chronoamperometry, and constant current deposition. The deposition of aluminum was found to proceed via a nucleation/growth mechanism, and the nucleation process was found to be progressive. The morphology of aluminum deposits was examined with photomicroscopy. It was shown that depending on the current densities (c.d.) applied, three types of aluminum deposits could be obtained, namely, spongy deposits formed at lower c.d. (below 0.7 mA/cm2), smooth layers deposited at intermediate c.d. (between 2 and 10 mA/cm2), and dendritic or porous deposits obtained at high c.d. (above 15 mA/cm2). However, the smooth aluminum deposits were about five times more voluminous than the theoretical value. The spongy deposits were formed due to difficulties in electronucleation and could be inhibited by application of pulsed currents and/or addition of manganese chloride into the melt.