Hydrophobic Coatings on Aluminum Substrate Based on Different Metal Oxides: Co₃O₄, ZnO, and MgO

The formation of different nanostructured metal oxides, Co₃O₄, ZnO, and MgO, has been carried out by thermal oxidation at 500°C using a low-cost electroplating technique at ambient temperature. The structure and morphology of the elaborated layers, along with their hydrophobic properties, have been investigated using various surface characterization techniques such as X-ray diffraction (XRD), Raman spectroscopy, field emission gun scanning electron microscope (FEG-SEM), and EDX analysis. The wettability properties of the elaborated coating were evaluated by measuring the contact angle between the surface of the films and a deposited water drop (WCA). The obtained results suggest the existence of metal oxide phases after thermal oxidation at 500°C with a nanometric crystallite size. Structural characterization by XRD demonstrates that the synthesized thin films were polycrystalline. The Raman analysis shows normal vibrational modes, which correspond to the structure of each thin film. The morphological study of elaborated thin film coatings illustrates the formation of nanometric grains distributed uniformly on the surface of each thin film. The surface morphologies change throughout the oxide type. The best hydrophobicity with WCA of 136.93° is obtained for MgO coating with nanowire morphology.