Anodic process on Cu-Al alloy in KF-AlF3-Al2O3 melts and suspensions
(School of Non-Ferrous Metals and Materials Science, Siberian Federal University, Krasnoyarsk, Russia)
Abstract: Anodic processes on Cu-10Al electrode in molten KF-AlF3-Al2O3 (saturated) and suspensions were characterized using chronopotentiometric and cyclic voltammetric techniques. Effects of cryolite ratio (CR= x(KF)/x(AlF3)), temperature and particle volume fraction (φ) on the electrochemical behaviour of the anode were demonstrated. Initially, the anode was polarised in the galvanostatic mode in melt and suspensions (φ=0.12, 0.15) at 750 °C with 0.4 A/cm2 current density. The anode potential in melt varied between 2.5 and 3.2 V and in suspensions (φ= 0.12) between 3.3 and 3.4 V. XRD analysis was conducted to study the oxide phases on the anode surface. Anode limiting current densities and mass transfer coefficients drastically decreased with the increase of φ in the suspension. The results suggest that the Cu-10Al electrode works better in suspensions with CR of 1.4 and particle volume fraction of 0.09 at 800 °C.
Key words: aluminium; suspension; oxidation; inert anode; cryolite melt; low-temperature electrolysis