The Influence of Polarisation on the Wetting of Graphite in Cryolite-Alumina Melts

The wetting properties of graphite were measured with the immersion/emersion technique in a high temperature alumina reduction cell. The wetting was measured at untreated, polarised and anode effect polarised samples. Most measurements were made in melts with 1 wt% alumina, although some measurements were performed at higher alumina content. As long as passivation (i.e. anode effect) was not initiated polarisation improved the wettability significantly and the wetting increased with increased polarisation. Anodes polarised to anode effect exhibited consistently very poor wetting. Most of the decrease in wetting occurred during the first few seconds of the anode effect, with full de-wetting from about 60 s.