Patent ID: 6077415
Filing Date: 2000-06-20
Classification: C25C

Abstract:
A composite, high-temperature resistant, non-carbon, metal-based anode of a cell for the electrowinning of aluminium by the electrolysis of alumina dissolved in a molten fluoride-containing electrolyte, the anode comprising a metal-based core structure of low electrical resistance, for connecting the anode to a positive current supply, coated with a series of superimposed, adherent, electrically conductive layers comprising:a) at least one layer on the metal-based core structure constituting during electrolysis a barrier substantially impervious to monoatomic oxygen and molecular oxygen;b) one or more intermediate protective layers on the outermost oxygen barrier layer to protect the oxygen barrier by inhibiting its dissolution, which intermediate layer(s) during electrolysis remain inactive in the reactions for the evolution of oxygen gas; andc) an electrochemically active layer on the outermost intermediate layer, for the oxidation reaction of oxygen ions present at the anode/electrolyte interface into nascent monoatomic oxygen, as well as for subsequent reaction for the formation of gaseous biatomic molecular oxygen;said active layer being slowly consumable during electrolysis and protecting said intermediate protective layer(s) by inhibiting its/their dissolution into the electrolyte.