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ArticleName Improvement of oxidation resistance of graphite blocks for the electrolytic production of magnesium by impregnation with phosphate solutions. Part 2
DOI 10.17580/tsm.2022.01.02
ArticleAuthor Feshchenko R. Yu., Eremin R. N., Erokhina O. O., Povarov V. G.

Saint-Petersburg Mining University, Saint-Petersburg, Russia:
R. Yu. Feshchenko, Associate Professor, Chair for Metallurgy, Candidate of Technical Sciences, e-mail:
R. N. Eremin, Leading Engineer of the Chair for Metallurgy, Candidate of Technical Sciences
O. O. Erokhina, Postgraduate student
V. G. Povarov, Leading Researcher, Doctor of Chemical Sciences


The previously obtained results were scaled up to increase the resistance to hightemperature oxidation of EGP (HP) electrode graphite. On an industrial scale, the contours of the technology for the manufacture of impregnated electrodes have been developed for their use in the electrolytic production of magnesium. The impregnation experiments were carried out in an autoclave in which the sample was hung on a weight strain gauge. Based on the data obtained, a kinetic curve of impregnation of the sample was built and the saturation time was determined. The required pre-degassing time was also determined empirically, which was at least three hours. Since the part of the anode located in the electrolyte melt of magnesium electrolyzers should not be impregnated, the samples were partially immersed in the solution during the experiment. To assess the increase in resistance to oxidation over the cross section of enlarged samples, cubes with an edge of 50 mm were sawn out of their impregnated part, which had a different number of sides in direct contact with the solution, i. e., those on which a continuous vitreous film was formed. The oxidation experiments were carried out in the isothermal holding mode at 800 oC for 5 h in a static volume of air. The results showed an increase in oxidation resistance over the entire cross section of the sample. Taking into account the conducted studies, a schematic diagram of a technology for obtaining oxidation-resistant graphite for magnesium electrolyzers has been developed. New methods have also been developed and well-known methods have been adapted to analyze the solution for the content of Al3+, Zn2+, PO42– ions and surfactants. The possibility of cleaning the circulating solution from the accumulated graphite suspension by thickening with the use of flocculants is shown.
The study was funded by a subsidy for the implementation of the state task in the field of scientific activity for 2021 No. FSRW-2020-0014.

keywords Graphite, electrode, impregnation, phosphates, resistance to hightemperature oxidation, titrimetry, electrolysis

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