Design and fabrication of nano textured superhydrophobic and anti-corrosive silane-grafted ZnO/bio-based polyurethane bilayer coating

Superhydrophobic polymer coatings are receiving special attention for industrial applications due to their multifunctionality behaviour. The advancement in nanotechnology has made it easier to design and fabricate nano-textured superhydrophobic coating on metal surfaces, even though adhesion and durability still remain a challenge. Therefore, the present study focuses on a novel bilayer coating approach for fabricating thermally stable, abrasion tolerant, multi-functional, superhydrophobic surface coating through the chemical bonding at the interface of hydroxy terminated polydimethylsiloxane modified cardanol-based polyurethane and silane grafted ZnO nanoparticles. The silane grafting to the ZnO surface has been confirmed by FT-IR, EDX, and XPS analysis. In addition, the change in crystallinity of unmodified and modified ZnO-based HTPDMS-CPU have been studied using XRD analysis. The superhydrophobic surface coating showed a high contact angle of 151° and contact angle hysteresis of 7° which got reduced after 10 cycles of abrasion to 133° and 12°, respectively. The silane groups at the surface allow ZnO to disperse uniformly and get exposed through the polymer coating while forming the micro/nano scale morphology. Furthermore, the anticorrosion parameters of the superhydrophobic bilayer coating showed corrosion current density (Icorr) value of order 10−9 (A.cm2) and corrosion potential (Ecorr) value of −0.351 (V) with inhibition efficiency (ƞ) of 99.5 % on mild steel. Thus, the superhydrophobicity, along with the excellent anticorrosion properties of this bilayer coating with a strong interface, chemical resistance and thermal stability elaborates its applicability in various fields.