The slag removal ability of flux is the ability of flux to adsorb and dissolve oxidized inclusions in melt, which is determined by the chemical interaction between solvent and melt.

Because the oxide inclusions are not wetted by liquid aluminium, the interfacial tension between them is very large, while the flux is wet to the oxide inclusions, and the interfacial tension between them is small. The surface free energy of the system can be reduced by adsorbing oxidized inclusions in the melt. Therefore, solvents have the ability to adsorb oxidized inclusions automatically, which is the main reason for flux slag removal. The smaller the interfacial tension between fluxes and non-metallic inclusions, the greater the interfacial tension between melts and metals, and the greater the interfacial tension between liquid aluminium and non-metallic inclusions, the better the adsorbability of fluxes and the stronger the slag removal effect.

The solubility of fluxes to oxides is determined by the nature of fluxes. Usually, when the molecular structure of solvents is similar to that of some oxides or their chemical properties are similar, mutual solubility can occur at a certain temperature. However, within the normal refining temperature range of aluminium melt, the solubility of alumina in fluxes is as follows: Very small.

The degassing effect of fluxes is to form gaseous products when the flux decomposes or interacts with the melt to diffuse dehydrogenation. In addition, because the oxide film on the surface of the melt is dissolved, it is easy for atomic hydrogen in the melt to diffuse to the atmosphere. However, the degassing effect of flux is limited. Under production conditions, its hydrogen content can only be reduced to about 0.2-0.25ml/100g.