The Electrodeposition of Aluminum from Nonaqueous Solutions at Room Temperature

Abstract

The electrodeposition of aluminum in the form of white or shiny adherent plates on various metals has been accomplished at room temperature. A satisfactory plating solution is prepared by mixing two moles of anhydrous aluminum chloride with 1 mole of ethyl pyridinium bromide, preferably in a dry, oxygen‐free atmosphere, to produce a liquid to which benzene (or toluene) is added until a second layer, principally excess benzene, forms on the top of the plating solution. Using an aluminum anode, plating may be carried out in a protected atmosphere at cathode current densities of approximately 1 amp/dm 2 (about 9 amp/ft 2 ) using voltages of the order of one volt. The use of an alternating current superimposed on the direct plating current ( a ) greatly improved adherence, e.g., a copper wire plated by this procedure can be repeatedly flexed without breaking the coating; ( b ) increased thickness without brittleness; ( c ) increased maximum current density; ( d ) somewhat lowered the voltage requirement; ( e ) gave the same efficiency based on the direct current; and ( f ) changed the appearance from shiny to satiny.