OPERATION OF ALUMINIUM ELECTROWINNING CELLS HAVING METAL-BASED ANODES

摘要

The present invention relates to a method of inhibiting fluorination and passivation of a metal-based anode having an alloy outer portion made of iron with nickel and/or cobalt and covered with an integral oxide surface layer facing a cathode in an aluminium fluoride-comprising molten electrolyte. This method comprises maintaining an amount of at least one basic fluoride, such as calcium or lithium fluoride, in the electrolyte to reduce the acidic activity of aluminium fluoride thereby inhibiting fluorination, corrosion of iron and passivation of nickel and/or cobalt of the alloy outer portion.