Voltage enhanced superhydrophobic ZnO micro/nanostructured coatings for anti-corrosion

Abstract

Superhydrophobic ZnO coating has been prepared by means of electrodeposited Zn layer on aluminium 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 studied. The samples have been investigated by field emission scanning electron microscope (FEG-SEM), energy dispersive X-ray analysis (EDX), profilometry/roughness measurements, X-ray diffraction (XRD), and Raman spectroscopy. The films wettability has been assessed via water contact angle (WCA) measurements. XRD and Raman spectroscopy analyses have confirmed the high crystallinity of elaborated ZnO thin films. FEG-SEM reveals potential-dependent morphology changes in the films. No impurity traces have been found, where EDX analysis has verified the presence only of Zn and O. Surface roughness has been observed to increase with rising negative potential from 1.356 μm for sample deposited at -10 V to 3.593 μm for sample deposited at -30 V, which has lead to an increase in contact angle values from 136.64° to 150.52°, respectively. Superhydrophobic ZnO surfaces with micro-nano topography have exhibited a hilly and valley shape. This has suggested that trapped air in surface valleys may successfully prevent corrosive wetting, such Cl-, from accessing the denuded surface, hence offering significant corrosion protection.