Growth of a superhydrophobic coating on an aluminium substrate with strong adhesive properties and showing efficient oil/water separation

This study focused on understanding the growth mechanism of a superhydrophobic (SH) coating with enhanced adhesive properties. A single-step process was used to generate an SH coating, which involved the electrochemical deposition of ZnCl2, alpha-Al2O3 and lauric acid (C11H23COOH) onto a commercially pure aluminium substrate. The superhydrophobic property of the coating was determined using the static contact angle (170 degrees). The sliding angle was also measured (1 degrees) to assess self-cleaning properties. Results of the spectroscopic techniques and field-emission scanning electron microscopy revealed that the coating had a flower-like structure composed of zinc laurate (Zn(C11H20COO)(2)). Field-emission scanning electron microscopy showed that the growth consisted of three main steps involving metallic nuclei and their oxidation, which led to the formation of new branches growing in different directions all over the surface. Two different tests demonstrated strong adhesive properties of the coating on an aluminium substrate. The coating also separated oil (hexane and petroleum ether) and water efficiently, therefore showing potential for environmental applications.