Electrochemical studies of magnesium ions in magnesium chloride containing chloride melt at 710 ± 10°C

Abstract

The electroreduction of magnesium ions on stainless steel and graphite substrates in magnesium chloride containing sodium chloride-rich NaCl + KCl + CaCl 2 melt at 710 ± 10° C has been studied using steady state voltanunetry, cyclic voltammetry, chronopotentiometry and chronoamperometry. The experiments were done in a controlled argon atmosphere cell with safety features. It is concluded that the mechanism of electrodeposition of magnesium in a purified melt is a reversible two-electron process in which the rate-determining step is the mass-transfer process. The non-steady state data also indicate minor effects of electron-transfer and electrocrystallization steps on the overall electrowinning process. The calculated values of the formal potential for the Mg/Mg 2+ electrode reaction and the diffusion coefficient of Mg 2+ ion are 2.75 ± 0.02 V vs. Cl −/Cl 2 (ref.) and (6.0±1.0)×10 −5 cm 2 s −1, respectively.