School of non-ferrous metals and material science, Siberian federal university, Krasnoyarsk, Russia:

A. S. Yasinsky, Associate Professor, Department of Non-ferrous Metallurgy, e-mail: ayasinskiykrsk@gmail.com
S. K. Padamata, Post-Graduate Student
P. V. Polyakov, Professor, De partment of Non-ferrous Metallurgy, e-mail: p.v.polyakov@mail.ru
O. O. Vinogradov, Head of teaching, research and production laboratory

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 CuAlO₂ compounds. 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 CuAl₂O₄ are 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.
This research was funded under the research project No. 18-48-243014 by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory, as well as the Regional Foundation for Support of Research and Development Work.

1. Galasiu I., Galasiu R., Thonstad J. Inert Anodes for Aluminium Electrolysis. Düsseldorf : Aluminium-Verlag, 2007. 212 p.
2. Tkacheva O., Spangenberger J., Davis B., Hryn J. Ch. 1.6. Aluminum Electrolysis in an Inert Anode Cell. Molten Salts Chemistry and Technology, First Edition. Ed. by M. Gaune-Escard, and G. M. Haarberg. N. Y.: John Wiley & Sons, 2014. pp. 53–69.
3. Haraldsson J., Johansson M. T. Review of measures for improved energy efficiency in production-related processes in the aluminium industry – From electrolysis to recycling. Renewable and Sustainable Energy Reviews. 2018. Vol. 93. pp. 525–548. DOI: 10.1016/j.rser.2018.05.043
4. Pawlek R. P. Inert anodes: an update. Light Metals. 2014. pp. 1309–1313.
5. Cassayre L., Patrice P., Pierre C., Laurent M. Properties of low-temperature melting electrolytes for the aluminum electrolysis process: a review. J. Chem. Eng. Data. 2010. Vol. 55. pp. 4549–4560.
6. Lebedev V. A., Shoppert A. A. Efficient Assessment of Physico-Chemical Properties of the Cryolite Melts for Research on the Improvement of Low-Temperature Aluminum Electrolysis. Materials Engineering and Technologies for Production and Processing. IV. Solid State Phenomena. 2018. Vol. 284. pp. 839–844. DOI: 10.4028/www.scientific.net/SSP.284.839
7. Jucken S., Schaal E., Tougas B., Davis B., Guay D., Roué L. Impact of a postcasting homogenization treatment on the high-temperature oxidation resistance of a Cu – Ni – Fe alloy. Corrosion Science. 2019. Vol. 147. pp. 321–329. DOI: 10.1016/j.corsci.2018.11.037
8. Galasiu I., Galasiu R. Aluminium electrolysis with inert anodes and wettable cathodes and with low energy consumption in: Molten Salts Chemsitry and Technology. Ed. M. Gaune-Escard, G. M. Haarberg. N. Y.: John Wiley & Sons, Ltd, 2014. pp. 27–37.
9. Gavrilova E., Goupil G., Davis B., Guay D., Roué L. On the key role of the Cu content on the oxidation behavior of Cu – Ni – Fe anodes for Al electrolysis. Corrosion Science. 2015. Vol. 101. pp. 105–113.
10. Yuan Wang, Han Bing He. The Ion Structure of NiFe₂O₄ – 10NiO – Based Cermet Anode in the Electrolyte. Materials Science Forum. 2018. Vol. 921. pp. 119–127. DOI: 10.4028/www.scientific.net/MSF.921.119
11. Oudot M., Cassayre L., Chamelot P., Gibilaro M., Massot L., Pijolat M., Bouvet S. Layer growth mechanisms on metallic electrodes under anodic polarization in cryolite-alumina melt. Corrosion Science. 2014. Vol. 79. pp. 159–168.
12. Ndong G., Xue J., Feng L., Zhu J. (2015) Effect of Anodic Polarization on Layer-Growth of Fe – Ni – Cr Anodes in Cryolite-Alumina Melts. 6^th International Symposium on High-Temperature Metallurgical Processing. Ed. T. Jiang et al. pp. 83–90.
13. Kovrov V. A., Khramov A. P., Zaikov Y. P., Chumarev V. M., Selivanov E. N. Anodic behavior of the NiO – Fe₂O₃ – Cr₂O₃ – Cu composite during the lowtemperature electrolysis of aluminum. Russ. J. Non-ferrous Metals. 2014. No. 55. pp. 8–14.
14. Meyer P., Gibilaro M., Massot L., Pasquet I., Tailhades P., Bouvet S., Chamelot P. Comparative study on the chemical stability of Fe₃O₄ and NiFe₂O₄ in molten salts. Materials Science and Engineering: B. 2018. Vol. 228. pp. 117–122.
15. Allanore A., Yin L., Sadoway D. R. A new anode material for oxygen evolution in molten oxide electrolysis. Nature. 2013. Vol. 497. pp. 353–357.
16. Zhiyuan Li, Zhongqi Shi, Zhejian Zhang, Rongdi Liu, Ying Liu, Jing Li, Guanjun Qiao. Corrosion resistance of the ZnCr₂O₄ spinel in NaF – KF – AlF₃ bath. Corrosion Science. 2018. Vol. 131. pp. 199–207.
17. Polyakov P. V., Klyuchantsev A. B., Yasinskiy A. S., Popov Y. N. Conception of “Dream Cell” in aluminium electrolysis. Light Metals. 2016. pp. 283– 288.
18. Yasinskiy A. S., Vlasov A. A., Polyakov P. V., Solopov I. V. Impact of alumina partial density on the process conditions of aluminium reduction from cryolitealumina slurry parameters. Tsvetnye Metally. 2016. No. 12. pp. 33–38.
19. Yasinskiy A. S., Polyakov P. V., Voyshel Y. V., Gilmanshina T. R., Padamata S. K. Sedimentation behavior of high-temperature concentrated colloidal suspension based on potassium cryolite. Journal of Dispersion Science and Technology. 2018. Vol. 39, Iss. 10. pp. 1492–1501.
20. Yasinskiy A. S., Polyakov P. V., Yushkova O. V., Sigov V. A. Spatial particle distribution during stokes sedimentation of alumina in high temperature concentrated suspension-electrolyte for aluminium production. Tsvetnye Metally. 2018. No. 2. pp. 45–50. DOI: 10.17580/tsm.2018.02.05
21. Nikolaev A. Yu., Suzdaltsev A. V., Polyakov P. V., Zaikov Yu. P. Cathode process at the electrolysis of KF – AlF3 – Al₂O₃ melts and suspensions. Journal of the Electrochemical Society. 2017. Vol. 164, Iss. 8. pp. H5315–H5321.
22. Hryn J., Tkacheva O., Spangenberger J. (2016) Initial 1000A Aluminum Electrolysis Testing in Potassium Cryolite-Based Electrolyte. Ed. B. A. Sadler. Light Metals. 2013. pp. 1289–1294.
23. Khramov A. P., Kovrov V. A., Zaikov Y. P., Chumarev V. M. Anodic behaviour of the Cu82Al8Ni5Fe5 alloy in low-temperature aluminium electrolysis. Corrosion Science. 2013. Vol. 70. pp. 194–202.
24. Shao W. Z., Feng L. C., Zhen L., Xie N. Thermal expansion behavior of Cu/Cu₂O cermets with different Cu structures. Ceram. Int. 2009. Vol. 35. pp. 2803–2807.
25. Shao W. Z., Xie N., Li Y. C., Zhen L., Feng L. C. Electric conductivity and percolation threshold research of Cu – Cu₂O cermet. Trans. Non-Ferrous Metals. Soc. China. 2005. Vol. 15. pp. 297–241.
26. Li-Chao Feng, Ning Xie, Wen-Zhu Shao, Liang Zhen, Ivanov V. V. Exploring Cu₂O/Cu cermet as a partially inert anode to produce aluminum in a sustainable way. Journal of Alloys and Compounds. 2014. Vol. 610, Iss. 15. pp. 214–223.
27. Feng L. C., Shao W. Z., Zhen L., Xie N. Microstructure and mechanical property of Cu₂O/Cu cermet prepared by in situ reduction-hot pressing method. Mater. Lett. 2008. Vol. 62. pp. 3121–3123.
28. Windisch C. F. J., Marschman S. C. Electrochemical polarization studies on Cu and Cu-containing cermet anodes for the aluminum industry. Light Metals. 1987. pp. 351–355.
29. Padamata S. K., Yasinskiy A. S., Polyakov P. V. Electrolytes and its Additives Used in Aluminum Reduction Cell: a Review. Metallurgical research and technology. 2019. Vol. 116, Iss. 4. pp. 410.