Increase of the part of graphitized cathode blocks used in the modern assemblies for production of primary aluminium via electrolytic method is recognized as the main direction of development of this technology. These blocks have a row of indisputable advantages, first of all low electric resistance and high level of electric conductivity. Increased abrasive hearth wear by alumina precipitants during melt motion seems to be the most important problem in operation of such blocks. This wear leads to decrease of service life of an electrolyzer and to increase of cost of manufactured metal. The leading global producers conduct complex works directed on quality improvement of graphitized blocks. These works include a row of scientific directions: rational selection of raw materials, selection of optimal parameters of the technological process, different variants of impregnations etc. Most of researchers agree that rise of density leads to lowering of abrasive wear, and that this effect can be achieved via different ways (first of all by pitch impregnation). Several technical solutions (e.g. creation of variable electric resistance along block length, with lower value close to edges, in the areas with increased wear) have peen confirmed via production testing and are used now successfully at a row of metallurgical works. In Russia graphitized blocks are not used practically. The project of Boguchansky aluminium works (planned to be put into operation in 2016) uses the blocks manufactured on the base of electrocalcinated anthracite with addition of 30 % graphite. Despite of the power engineering potential of Siberian region, such approach is inexpedient, taking into account the fact that high power expenses caused closure of a row of aluminium works in the European part of Russia. Accumulated global experience can be the base for development of science-intensive solutions in the Russian electrode industry and their consequent putting into operation, what in its turn will allow to achieve correspondence between quality of manufactured commercial products and requirements of customers.

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Graphitized electrodes are broadly used in industry. However, when they are used in high-temperature operating environments, they are subject to oxidation, which can lead to abnormal operation or premature failure of an electrolytic cell. Use of protective coatings or special wetting solutions (melts) help increase the oxidation resistance of a wide assortment of components. It is obvious that a coating that covers an electrode completely will hinder or stop the electric current from flowing at the electrode/electrolyte boundary, which makes this technique inapplicable to anodes for magnesium electrolysis. Aqueous solutions of phosphates are widely used around the world to make materials more resistant to high-temperature oxidation due to the formation of glassy phases during drying. This paper examines the efficiency of using a mixture of zinc and aluminium dihydrophosphates dissolved in an aqueous solution of orthophosphoric acid to enhance the oxidation resistance of the graphite electrode EGP (NR). A comprehensive thermal analysis was carried out to examine the solution for suitability. And X-ray diffractometry helped verify the formation of crystals after the solution had been dried. Cube-shaped specimens with the side length of 50 mm were used in the experiments aimed at identifying optimum graphite wetting and drying conditions. Isopropanol was used as a surfactant to ensure proper wetting. The specimens were first subjected to vacuum degassing for air to be removed from the pores, and then they were soaked in a rarefied solution. A kinetic model was selected to describe the post-wetting drying procedure. The oxidation resistance was analyzed in a dynamic air flow. The experiments were carried out at 700 oC as it is the highest possible temperature for magnesium electrolysis. The results of the experiments showed that the above wetting technique, when applied in a laboratory environment, helped achieve a five-fold increase in the oxidation resistance of the model graphite electrodes. The authors looked at the feasibility of scaling the experiments and developing process circuits to produce graphite with high oxidation resistance.

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