Anti-corrosion behavior of superhydrophobic aluminum coatings based on micro/nanostructured ZnO: Impact of applied DC voltage

Abstract

Superhydrophobic ZnO coating has been prepared by means of electrodeposited Zn layer on aluminum substrate, followed by thermal oxidation at 500°C. In this work, the impact of applied negative potential on the physical characteristics of ZnO coatings has been investigated. The samples were characterized by scanning electron microscopy (FEG-SEM) equipped with energy dispersive X-ray analysis (EDX), a Profilometer-Roughness Tester, X-ray diffraction (XRD), and Raman spectroscopy. The wettability properties of the synthesized films were evaluated by measuring the contact angle between the surface of the films and a deposited water drop (WCA). XRD and Raman spectroscopy analyses have confirmed the high crystallinity of elaborated ZnO thin films. FEG-SEM images show that the surface morphologies of prepared films change throughout the applied negative potentials. No traces of contaminants were discovered where EDX analysis check the presence only of Zn and O. The wettability properties of the elaborated films were evaluated by measuring the water contact angle on the surface of the films (WCA). The surface roughness increases with the increase in the applied negative potential from 1.356 μm for sample deposited at -10 V to 3.593 μm for sample deposited at -30 V, which leads to an increase in contact angle values from 136.64° to 150.52°, respectively. Superhydrophobic ZnO surfaces with micro-nano topography have a hilly and valley shape. This means that air trapped in the "valleys" may successfully prevent corrosive fluids, such Cl^-, from accessing the denuded surface, hence offering significant corrosion protection.