Tuning of hydrophobicity of WO₃-based hot-dip zinc coating with improved self-cleaning and anti-corrosion properties

Hot-dip galvanic (ZnAl) coatings with enhanced self-cleaning and anti-corrosion attributes were developed through effective incorporation of WO₃ nanoparticles. The wet-synthesized WO₃ nanoparticles were systematically characterized for crystallinity, optical properties, bonding characteristics, compositional purity, chemical state, morphology, size distribution, and colloidal and thermal stability; and successfully assimilated into the galvanic coating. High water contact angles (112.3°) recorded for the composite coating revealed improved hydrophobicity of the tuned surface. The coating displayed excellent self-cleaning property against the applied dirt particles. The hydrophobic WO₃ nanoparticles-incorporated coating exhibited superior anti-corrosion performance than the conventional bare ZnAl coating as revealed by scanning Kelvin probe microscopic studies, long-term potential measurements, Tafel polarization and impedance spectroscopy. The composite coating exhibited high charge transfer resistance (280.20 Ω.cm²) and low corrosion rate (6.54 × 10⁻⁶ mmpy) along with enhanced mechanical and tribological properties. The better performance of the composite coating was attributed to the combined ‘barrier-hydrophobic-sacrificial’ effect of the WO₃-incorporated ZnAl coating.