High-Temperature Wetting Behavior and Adhesion Mechanism of Cryolite-Based Molten Salt on SiC Refractory Substrate

The problem of the adhesion of aluminum slag to the inner wall of a vacuum ladle is essential but has not been addressed. Using a high-temperature wettability experimental setup, this paper investigates the mechanism of interfacial wettability, adhesion, and penetration between Na3AlF6-Al2O3-CaF2 cryolite-based molten salt and SiC refractory substrate. The composition of the slag was determined based on the slag obtained in the transfer ladle during the aluminum electrolysis process. We mainly study the effects of different Al2O3 contents in cryolite-based molten salt and temperatures on the contact angle and surface tension. The results indicate that as the Al2O3 content in the slag increases, the contact angle decreases, enhancing the slag’s wettability on the SiC substrate. Additionally, a higher Al2O3 content leads to higher slag melting temperatures and surface tension, which improves the slag mobility and enhances the mass transfer and diffusion capabilities of molecules or ions within the slag. The work of adhesion, calculated using the Mills model, also increases with the increasing Al2O3 content. The increased Al2O3 concentration activates the activity of Na3AlF6 in the slag, facilitating the dissolution reactions and improving the wettability between the slag and SiC. Moreover, the wetting behavior of the Na3AlF6-Al2O3-CaF2 slag is primarily influenced by the initial Al2O3 content and its compositional changes. The results show that the slag penetration resistance and mechanical erosion resistance of the ladle lining can be improved by using an SiC-based refractory with an optimized Al2O3 content. This will have important guiding significance for the development, design, and application of inner wall materials for aluminum electrolysis industrial vacuum ladles.