Robust and superhydrophobic coating highly resistant to wear and efficient in water/oil separation

Abstract

Here, we report a straightforward and rapid process using fatty acids to produce a stable superhydrophobic hybrid composite coating on aluminium substrate which is highly resistant to wear under environmental conditions. Furthermore, this novel superhydrophobic metal surface is highly efficient at separating of water/oil systems. The single-step process we adopt involves electrochemical deposition of ZnCl2, α-Al2O3 and lauric acid (C11H23COOH) onto commercial pure aluminium substrate. The resultant static contact angle (170°) and sliding angle (1°) are those of a superhydrophobic coating with self-cleaning properties; while chemical analysis shows that this is the result of generation of zinc laurate (Zn(C11H20COO)2) as a major compound that increases the superhydrophobic character of the coating, generating a flower-like structure 70 nm thick. Different wear tests show the coating is resistant to severe conditions, confirming its real potential against weathering, including sand and water erosion. Finally, a water/oil separation test determined 99% separation efficiency in hexane and ether petroleum systems, in a laboratory-made storage tank.