The role of magnesium fluoride in electrolytic aluminum production

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①Magnesium fluoride can lower the melting point of the electrolyte. ②Magnesium fluoride can increase the surface tension of the electrolyte, which is beneficial in reducing the loss due to re-dissolution of aluminum and facilitating the separation of carbon slag within the electrolyte ； Therefore, MgF2 indirectly contributes to improving the electrical conductivity of the electrolyte, and its effect in this regard is greater than that of calcium fluoride. ③Magnesium fluoride is a mineralizing agent that accelerates the mineralization of α-Al2O3, which is beneficial for forming a stable crust on the side walls of the electrolyzer. ④Furthermore, the electrolyte crust with added MgF2 is loose and easy to break apart. 　　However, the downside is that magnesium fluoride reduces the solubility and dissolution rate of alumina to some extent, increases the density of the electrolyte, and slightly lowers its electrical conductivity. Therefore, MgF2 is only added near the walls of the furnace, not inside it, in order to avoid the formation of excessive deposits beneath the anode. Aluminum plants in our country adopt the practice of \"frequent processing and less material usage\", which can compensate for the disadvantages caused by the addition of MgF2. Therefore, magnesium fluoride is a beneficial additive. It is generally added at 4–6%, and the effect of adding calcium fluoride is essentially the same as that of MgF2.