Fabrication of a leaf-like superhydrophobic CuO coating on 6061Al with good self-cleaning, mechanical and chemical stability

Abstract

Copper oxide is widely used to obtain superhydrophobic surfaces due to its special micro/nano-structures and properties. However, there are few studies on a leaf-like CuO superhydrophobic coating by direct thermal oxidation of Cu on 6061Al substrate. In this work, there is a simple and low-cost method including chemical replacement, thermal oxidation and low-energy-modification with stearic acid. The resultant coating is superhydrophobic and oleophilic with water contact and sliding angles of 157.3∘±0.5∘ and 3.6∘±1∘, respectively. Additionally, it has low adhesion and excellent self-cleaning performances, whose corresponding mechanical analyses are conducted to theoretically discuss that stable micro/nano-structures and trapped air pockets could effectively influence the interfacial adhesion. Importantly, after tape-peeling, sandpaper-abrasion, and chemical stability tests, the coating still keeps superhydrophobic. Especially, in 3.5 wt% NaCl aqueous solution, compared with the corrosion current density of bare 6061Al substrate (7.18×10−7A/cm2), that of the SHP CuO coating (0.77×10−7A/cm2) decreases obviously. In sum, the method is especially suitable for large-scale industrial production of a stable superhydrophobic coating on Al alloys.