Modifier-free fabrication of durable superhydrophobic electrodeposited Cu-Zn coating on steel substrate with self-cleaning, anti-corrosion and anti-scaling properties

Modifier-free superhydrophobic surfaces have attracted much attention since their discovery due to the potential for applications. Although there is an emerging consensus that modifier-free structured hydrophilic surfaces can achieve superhydrophobic, how the surface morphology influence their wettability as well as why modifier-free structured surfaces can achieve superhydrophobic are lacking. In this work, we fabricated many Cu-Zn coatings with various surface morphologies on steel substrate by tuning electrodeposition parameters including the current density, the Zn2+/Cu2+ molar ratio, and the electrodeposition time. We found that these freshly prepared electrodeposited Cu-Zn coatings were superhydrophilic after dried. Interestingly, after storage in air for more than 60 days, these modifier-free hierarchical structured Cu-Zn coatings became superhydrophobic with the maximum water contact angle of 154.73 degrees and the minimum sliding angle of similar to 6.5 degrees. We experimentally demonstrated that both the hierarchical structure and the chemical composition (the formation of CuO-ZnO and the oxygen adsorption) contribute to the superhydrophobicity of the modifier-free Cu-Zn coating. Furthermore, this modifier-free superhydrophobic Cu-Zn coating presents excellent durability, self-cleaning, anti-corrosion, and anti-scaling properties.