Anomalous Al-Mg Electrodeposition Using an Organometallic-Based Electrolyte

The Al-Mg electrodeposition is investigated using the organometallic-based electrolyte: Na[AlEt4]+2Na[Et3Al-H-AlEt3]+2.5AlEt(3)+6toluene (Et =-C2H5), employing Mg anode. With an increase of Mg in the deposit the predominant morphology and its composition changes from ground (90-95 atom% Al) to smooth globules (75-80 atom% Al) to rough globules (15-45 atom% Al). The ground and smooth globules possessed face centered cubic (fcc) Al(+Mg) phase and the rough globules possess hexagonal close packed (hcp) Mg(+Al) phase. The overall composition (atom% Al-the more noble metal) of the deposits is less than that of the electrolyte, and increases steeply with a slight change in the latter. This indicates the absence of preferred deposition of the more noble metal suggesting the anomalous electrodeposition of Al-Mg. A critical ratio of Al/Mg exists in the electrolyte beyond which the anomalousness is enhanced. This critical ratio is identified by the onset of hcp Mg(+Al) phase formation in the deposits. A lack of trend in the overall deposit composition with electrolyte agitation affirms the anomalous electrodeposition of Al-Mg system under present experimental conditions. (C) 2016 The Electrochemical Society. All rights reserved