Eco-Friendly Superhydrophobic Graphene Oxide/Silica Coating by Cathodic Electrophoretic Deposition

Despite the unprecedented attention to the environmental impacts of coatings, no study on superhydrophobic coating using graphene oxide and silica has been conducted to fill this research gap. The present study aims to develop a low-cost, environmentally friendly method for producing superhydrophobic coatings to protect 5052 aluminum alloy. The main goal is to achieve hydrophobicity without relying on toxic secondary surface modification processes. In this regard, a two-step process including chemical etching (to create a hierarchical micro-nano structure) followed by cathodic electrophoretic deposition (EPD) from a suspension containing graphene oxide (GO) and silica nanoparticles (SiO2) was employed. The raw materials and final coating were analyzed using techniques such as X-ray Diffraction (XRD), Hydrogen-1 Nuclear Magnetic Resonance (HNMR), Field-Emission Scanning Electron Microscopy (FE-SEM), Static contact angle (CA), Dynamic contact angle (DCA), and Fourier-Transform Infra-Red Spectroscopy (FTIR). The findings revealed a uniform “cauliflower-like” microstructure, with an average static contact angle of 162° and a residual contact angle of 4°, demonstrating superhydrophobic properties. FT-IR analysis revealed that the EPD process effectively reduced graphene oxide from its oxidized state and released hydrophilic functional groups on the surfaces of SiO2 and graphene oxide. Two distinct bands are observed at wavenumbers 2857 cm⁻¹ and 2903 cm⁻¹, which are assigned to the symmetric and asymmetric stretching vibrations of the methyl groups (–CH₃). These bands are related to the presence of –SiOCH₃ groups in the structure. These dual effects also made the coating naturally hydrophobic without needing extra steps, such as additional heat or chemical treatments.