Sol–gel derived highly hydrophobic Polystyrene/SiO2 spray coatings on polished stainless steel and textured aluminium substrates

Abstract

ABSTRACT In this study, sol–gel derived spray coatings of highly hydrophobic nature consisting of polystyrene (PS) and SiO2 nanoparticles were developed on polished stainless steel 321 (SS) and textured 6061 aluminium (Al) alloy substrates. The micro-structures on the Al surface were created through ultraprecision machining, known as single-point diamond turning (SPDT) machining. The polished SS and micro-structured Al were coated with PS/SiO2 using a spray coating technique by maintaining a pressure of 4–5 kPa, and positioning the nozzle 20–30 cm away from the substrates. The textured surface of Al was characterised using coherent correlational interferometry (CCI). The PS modified SiO2 nanoparticles and their coatings were characterised using Fourier-Transform Infrared Spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM). The resulting coating exhibited a micro-nano hierarchical roughness due to the presence of SiO2 nanoparticles and their fine size clusters. The polished SS surface showed static water contact angles of 93.3° and 143.5° before and after coating, respectively. Similarly, the polished and coated structured Al surface exhibited water contact angles of 85.6° and 144.3° before and after coatings. Such coatings can exhibit a great potential particularly in the field of self-cleaning technologies.