Physical-chemical properties of molten salt media based on potassium cryolite with additions of boron or scandium oxides have been considered from the point of view of their feasibility in production of functional materials, such as aluminum alloys. Liquidus temperature in the quasi-binary systems: [KF–AlF3]-B2O3, [KF–AlF3]-Sc2O3, [KF–NaF–AlF3]-B2O3, and [KF–NaF–AlF3]-Sc2O3 has been measured by thermal analysis. Solubility of Al2O3, B2O3, and Sc2O3 in potassium and potassium-sodium cryolites has been determined. The potassium-cryolite-based melts were found to have an enhance protective function due to a low melting point, and an effective refining ability due to a good alumina solubility. It has been assumed that for aluminum alloys production the potassium-cryolite-based melts can be used as fluxes with improved properties as well as electrolytes for low-temperature electrolysis