Coalescence behavior of aluminum alloy drops in molten salts

The coalescence of aluminum and aluminum alloy drops in molten salt flux was observed in different salt fluxes as a function of time. Salts based on equimolar NaCl-KCl with addition of other metal chlorides or metal fluorides were used. All salts showed the ability to coalesce metal drops into one drop, but time taken for complete coalescence was different for different salts. Metal drops are covered with oxide film, which hinders their ability to coalesce into one metal drop. Thus, the coalescence ability of any salt depends on the efficiency of oxide removal by the salt. Removal of oxide layer from aluminum surface by equimolar NaCl-KCl and equimolar NaCl-KCl containing 5 mass%NaF was observed by interference microscopy. It was found that the oxide layer was not removed by equimolar NaCl-KCl, while it was removed by equimolar NaCl-KCl containing 5 mass%NaF. Coalescence ability of salt is related to weight loss of metal in salt and interfacial tension between metal and salt.