Wetting of KF-ALF3-based melts on graphite cathode materials for aluminum electrolysis

Abstract

Graphite cathode materials are nowadays used in aluminum reduction process where KF-AlF3-based melts may serve as an alternative electrolyte. In this work, wetting angles of KF-AlF3-based melts on graphite cathode materials were measured using a modified sessile drop method. A fresh drop of the melt was injected through a BN tube on to the samples surface, and then the wetting angles were photographed against time elapsed. It was found that the wetting angles on the full graphitic and graphitized cathode samples were larger than those on the semi-graphitic at 750 °C, and their values changed with varying alumina content (3-5 wt%), cryolite ratio (1.2-1.5) and time (0-20 min). The melt penetration profiles on the cross-sections of the melt-graphite interface after wetting tests were also inspected using SEM-EDS technique. In addition, ultrasound was introduced into the cathode through a stainless steel rod and its effect on the wetting of melts was investigated.