An Inert Metal Anode for Magnesium Electrowinning

Abstract

Results from the development of a novel type of anode for electrowinning Mg are reported. A tailored alloy system based on the binary Cu-Al can be made to forma tlin alumina layer on its surface that is relatively impervious to attack by the molten chloride melt at high temperature. This barrier is thin enough (5-50nm) to conduct electrical current without significant IR loss. As the layer slowly dissolves, the chemical potential developed at the surface drives the diffusion of aluminum from the bulk alloy to reform (heal) the protective alumina layer. In this way, an anode that generates Clz (melt electrolysis) and 02 (wet feed hydrolysis) and no chlorocarbons can be realized. Further, we expect the rate of loss of the anode to be dramaticallyy less than the coke-derived carbon anodes typically in use for this technology, leading to substantial cost savings and ancillary pollution control by eliminating coke plant emissions, as well as eliminating chlorinated hydrocarbon emissions from Mg electrowinning cells.

Development of Inert Anode Materials for Electrowinning in Calcium Chloride Melts

“…Whilst there have been extensive efforts in the aluminium industry to identify stable inert anode materials (10,11), and some effort for magnesium (12)(13)(14), few reports have appeared specifically for titanium (15). The present study examines the stability of candidate anode materials for the electrowinning of titanium in a calcium chloride-based melt at 950°C and performance in laboratory-scale electrolysis tests.…”