Corrosion behavior of Cu-Ni-Ag-Al alloy anodes in aluminium electrolysis①
(School of Materials & Metallurgy, Northeastern University, Shenyang 110004, China)
Abstract: The behavior of Cu-Ni-Ag-Al alloy used as anode for aluminum electrolysis was directly visualized in a twocompartment see-through cell during electrolysis, and its performances were tested at 850℃in acidic electrolyte molten salts consisting of 39.3% NaF-43.7% AlF3-8% NaCl-5% CaF2-4% Al2O3for 40 h in a laboratory cell. The results show that nascent oxygen oxidizes the anodic surface to form oxide film at the beginning of electrolysis. X-ray diffraction analysis of alloy surface show that the oxide film on the anodic surface consists of CuO, NiO, Al2O3, CuAl2O4and NiAl2O4. However, SEM image shows the oxide film is porous, loose and easy to fall into electrolyte and to contaminate aluminum. The corrosion mechanism of metal anodes was analyzed.
Key words: metal anodes; aluminum electrolysis; oxide film; porous; corrosion mechanism