Techniques for forming an enclosure comprised of aluminum zirconium alloy layer are disclosed. In some embodiments, aluminum ions and zirconium 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 zirconium ions onto a metal substrate. The resulting aluminum zirconium alloy layer can include nanocrystalline grain structures, which can impart the alloy layer with increased hardness and increased resistance to scratching, denting, and abrasion. In some embodiments, the aluminum zirconium alloy layer can be anodized to form an aluminum oxide layer. Subsequent to the anodization operation, the oxidized layer is able to retain its substantially neutral color.