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How is fluorine used in aluminum refining?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — halogen Modern version of the periodic table of the elements.

In the industrial production of aluminum, fluorine is essential as a key component of the electrolyte used in the Hall-Héroult process.12

During smelting, alumina (aluminum oxide) is dissolved in a molten bath consisting primarily of cryolite, a compound of sodium, aluminum, and fluorine (Na₃AlF₆). This molten mixture acts as a solvent that allows the alumina to be reduced to metallic aluminum through electrolysis.134

Because some fluoride is inevitably lost during the continuous smelting process, aluminum fluoride is added periodically to the reduction pots to restore the bath's chemical composition and maintain maximum efficiency. While natural cryolite is rare, the industry relies on synthetic cryolite, which is manufactured using fluorine sources such as fluorspar.1342