ELECTRODEPOSITION OF ALUMINIUM-COPPER ALLOYS FROM ALKYL BENZENE ELECTROLYTES

An experimental programme in which aluminium-copper alloys were electroplated from alkyl benzene/ AlBr3 electrolytes is described. The investigation showed that Al-Cu alloys (0-3.5 wt% Cu) can be plated onto steel and that the resulting coatings are bright, adherent and less porous than equivalent coatings of pure aluminium. The composition of the cathode deposits can be readily controlled by using Al-Cu anodes of specified copper content. About half the copper dissolved from the anodes is transferred to the cathode, the remainder being precipitated from the electrolyte as CuBr. Coating composition varies with current density and this parameter can also be used to control the process. In a parallel investigation, potential differences between aluminium and a number of other metals (Zn, Pb, Cd, Sn, Cu, Ag) were measured. Potential differences in the alkyl benzene electrolytes were found to be 10-30 times less than in aqueous electrolytes which indicates that the alkyl benzenes should be useful for plating other alloys in addition to those of aluminium and copper. © 1979 Chapman and Hall Ltd.