Self-healing superhydrophobic coating with durability based on EP + PDMS/SiO2 double-layer structure design

Superhydrophobic coatings often face challenges related to poor friction and corrosion resistance. In this study, composite coatings were developed, featuring a top layer of SiO2 nanoparticles and a bottom layer of epoxy resin (EP) and polydimethylsiloxane (PDMS). As the number of SiO2 nanoparticles layers increased, surface roughness escalated, and the coating structure transitioned from SiO2 nanoparticles entirely encapsulated by EP and PDMS to a small fraction of SiO2 exposed on the coating surface. Leveraging the rough surface and low-free-energy properties endowed by Si-(CH3)2 and Si-O-Si hydrophobic groups, coatings comprising 3–5 layers SiO2 nanoparticles exhibited superhydrophobicity and self-cleaning capabilities. These coatings retained their superhydrophobic properties even after enduring heavy friction from sandpaper, and demonstrated robust corrosion resistance over extended periods. Increasing the number of SiO2 layers not only enhanced superhydrophobicity, corrosion and friction resistance, but also improved the coating-substrate adhesion. The designed coating structure exhibited superior corrosion resistance and coating-substrate adhesion compared to those of EP/PDMS + SiO2 double-layer and EP + PDMS + SiO2 mixed coatings. Moreover, the coatings displayed a self-healing ability, regaining superhydrophobicity following O2 or Ar etching, facilitated by the upward movement of hydrophobic groups/bonds and intensity recovery. Coatings subjected to Ar etching exhibited better self-healing properties due to higher Si-O-Si and lower C-C/C-H bond intensities. This research presents novel insights for the practical application of superhydrophobic coatings.