Interfacial tension between aluminum and NaCl-KCl-based salt systems

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 1998-08, Vol.29 (4), p.821-827
• Main Authors: ROY, R. R, UTIGARD, T. A
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Metallurgical fundamentals; Metals. Metallurgy; Production of metals
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-998-0141-8

Aluminum scrap is frequently remelted under a NaCl-KCl based salt flux cover to prevent oxidation, to aid in the stripping of oxide films, and to improve drop coalescence. In this process, the interfacial tension between the Al metal and the salt flux plays an important role. However, the measurement of interfacial tensions at high temperature is difficult and prone to errors. Therefore, an interfacial tension model, presented in this article, has been developed. The interfacial tension between Al and NaCl-KCl based melts does not change with the addition of chlorides or with variations in the composition of the NaCl-KCl melt. On the other hand, the addition of fluorides decreases the interfacial tension to various extents due to the adsorption of sodium and/or potassium at the interface. Addition of AlF sub 3 is the least effective; additions of LiF, MgF sub 2 , CaF sub 2 , BaF sub 2 , or SrF sub 2 are moderately effective; and additions of NaF or KF are the most effective in lowering the interfacial tension.