Anodic process on aluminium bronze in low-temperature cryolite-alumina melts and suspensions

Abstract

The work is devoted to the anodic behaviour of Cu–Al-based alloys in cryolitealumina melts and suspensions with a cryolite ratio 1.3 and a volume fraction of the dispersed phase in suspensions 0.12 and 0.15 with analytical alumina with average particle size 5 μm. The alloys were investigated by the methods of stationary galvanostatic polarization and cyclic voltammetry. The experiments were carried out at 1023 K. Alloys Cu – 9 Al – 5 Fe (composition A1), Cu – 10 Al (A2) and Cu – 10 Al – 1.7 Be (A3) were used as anodes, the possible oxidation products of the anodes were thermodynamically analyzed, and the standard electrode potentials of the corresponding reactions were calculated. After the experiments, the structure of the oxide layer was investigated. The metal is covered with a dense 0.5–1 mm thick oxides layer. Visible cracks, damage and signs of deep corrosion were not found. The oxide layers of the samples consist mainly of Cu2O and CuAlO2compounds. The transition from the saturated melt to the suspension leads to an increase in the fraction of copper (I) oxide in the oxide layer. The compounds CuO and CuAl2O4are found only in the oxide layers of the anodes of composition A2. Composition A2 and suspensions with the dispersed phase volume fraction of not more than 0.12 are recommended for further research.