The electrodeposition of magnetic cobalt-aluminum alloys was investigated in the Lewis acidic aluminum chloride-1-methyl-3-ethylimidazolium chloride (60.0-40.0 mole %) molten salt containing electrogenerated Co(II) at 25 °C. Alloy deposits containing up to 62 atomic % aluminum were produced at potentials positive of that for the bulk deposition of aluminum. The onset of the underpotential driven aluminum co-deposition process occurred at around 0.40 V versus the A1/A1(III) couple. The Co-Al

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... y composition displayed an inverse dependence on the Co(II) concentration, but tended to become independent of concentration as the potential was decreased. A RRDE voltammetry technique was developed to analyze the composition and structure of the Co-Al alloy deposits. SEM-EDS analysis of bulk electrode posits revealed that the deposit morphology depends strongly upon the aluminum content/deposition potential; deposits produced at 0.40 V consisted of 1 0 -2 0 pm diameter multifaceted nodules of pure hep cobalt whereas those obtained at 0.20 V were dense and fine grained, containing about 4 atomic % Al. Deposits produced at 0 V had the visual appearance a o f loosely adherent black powder. XRD diffraction measurements revealed a lattice expansion and a decrease in grain size as the hep cobalt was alloyed with increasing amounts of aluminum.