Superhydrophobic coatings fabricated with polytetrafluoroethylene and SiO2 nanoparticles by spraying process on carbon steel surfaces

Abstract

Superhydrophobicity is extensively investigated because of the numerous methods developed for water-repellant interface fabrication. Many suitable functional materials for the production of superhydrophobic surfaces on various substrates are still being explored. In this study, inorganic SiO2 and organic polytetrafluoroethylene (PTFE) nanoparticles (NPs) are used for a comparative study on the performance of superhydrophobic coating on carbon steel surfaces. The NPs are added to PTFE coating emulsions by physical blending to form coating mixtures. Raw SiO2 NPs are then hydrophobized using KH-570 and validated by Fourier transform-infrared spectroscopy (FT-IR) and Dynamic Laser Scattering (DLS) grain size analyses. The microstructures of the surfaces are characterized by contact angle (CA) measurements and field emission-scanning electron microscope (FE-SEM) images. The prepared surfaces are subjected to adhesion, hardness, water resistance, and acid/alkali erosion tests. Hydrophobized SiO2-filled coating surfaces are found to have better uniformity than raw SiO2 regardless of their similar maximum static contact angles (SCAs) about 150°. A SCA of 163.1° is obtained on the PTFE NP-filled coating surfaces that have a considerably denser structure than SiO2. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses reveal that all fabricated surfaces have good thermal stability and tolerate temperatures up to 550°C. The PTFE NP-filled coating surfaces also exhibit excellent water and acid resistance. A possible mechanism concerning the amount of trapped air is proposed in relation to practical superhydrophobic surface fabrication.