Improving corrosion resistance of Cu-Al-based anodes in KF-AlF3-Al2O3 melts
(1. Laboratory of Physics and Chemistry of Metallurgical Processes and Materials, Siberian Federal University, Krasnoyarsk, Russia;
2. Laboratory of Molecular Spectroscopy, Krasnoyarsk Science Center SB RAS, Krasnoyarsk, Russia;
3. School of Metallurgy, Northeastern University, Shenyang 110819, China)
2. Laboratory of Molecular Spectroscopy, Krasnoyarsk Science Center SB RAS, Krasnoyarsk, Russia;
3. School of Metallurgy, Northeastern University, Shenyang 110819, China)
Abstract: The anodic behaviour of pre-oxidised and non-oxidised Cu-Al-based anodes (Cu-10Al and Cu-9.8Al-2Mn) in KF-AlF3-Al2O3 melts was studied through galvanostatic and potentiodynamic polarization techniques. The alloy compositions were oxidised for a short-term (8 h) at 700 °C, followed by galvanostatic polarization for 1 h at 800 °C with an applied current density of 0.4 A/cm2. The potentiodynamic curves were recorded with a sweep rate of 0.01 V/s. XRD analysis was conducted on frozen melt samples collected on the surface of the anode, and SEM observation was performed on the anode after the experiment to study the phases of the scales formed on the alloys. All the anode materials had a steady potential between 2.30 and 2.50 V (vs Al/AlF3). The corrosion rates of the anodes were calculated from the data acquired through potentiodynamic polarization. It was seen that pre-oxidised anodes possess a low corrosion rate compared to those without pre-oxidation treatment.
Key words: inert anodes; potassium cryolite; Cu-Al alloys; corrosion; aluminium electrolysis; oxygen-evolving electrodes