Techniques for forming an enclosure comprised of an aluminum alloy are disclosed. In some embodiments, aluminum ions and metal element ions can be dissolved in a non-aqueous ionic liquid in an electrolytic plating bath. A reverse pulsed electric current can facilitate in co-depositing the aluminum ions and the metal element ions onto a metal substrate. The resulting aluminum alloy layer can include nanocrystalline structures, which can impart the alloy layer with increased hardness and increased resistance to scratching, corrosion, and abrasion. In some embodiments, the metal element ion is chromium and the aluminum alloy layer includes a chromium oxide passivation layer formed via a passivation process. Subsequent to the passivation process, the formation of the chromium oxide layer does not impart a change in color to the aluminum alloy layer. In some embodiments, hafnium ions are co-deposited with aluminum ions to form an aluminum hafnium alloy.