Interaction and interfacial tension between aluminum alloys and molten salts

Abstract

The interaction between liquid aluminum and molten salts was studied by metal loss and electrochemical methods. The polarization curves for Al and Used Beverage Container (UBC) alloy in molten salts show that the corrosion rate of UBC is higher than that of pure Al, and the corrosion rate is higher in the equimolar NaCl-KCl+5%NaF salt melt than in equimolar NaCl-KCl molten salt. It was found that magnesium in aluminum alloys dissolves preferentially into these molten salts. This can be rationalized by the more negative free energy of MgF2, or the lower electrode potential EMg/Mg2+ compared to EAl/Al3+. The metal loss in molten salts increases with time and addition of fluorides. It was found that the metal loss in molten salt was inversely related to the metal and molten salt interfacial tension. Finally, the Girifalco and Good model was used to calculate the interfacial tension between UBC alloy and molten salts based on an interaction parameter calculated from the interfacial tensions between pure aluminum and molten salts. The predicted values are in reasonable agreement with the measured values of interfacial tension.