Enhanced hydrophobicity of polyurethane coating for steel protection through replication and nanomaterial integration

Polyurethanes (PU) are widely used in corrosion protection, anti-biofouling coatings, and self-cleaning glass, yet their low hydrophobicity poses durability challenges. This study addresses this by enhancing PU coatings’ hydrophobicity by refining surface roughness and forming tailored porous structures. Using drop, spin, dip, and spray coating techniques, hydrophobic PU coatings were fabricated on 304 steel plates. To further enhance hydrophobicity, 0.5 w/v% graphene nanoplatelets (GNP) were introduced into the coatings. Additionally, stainless-steel 500 mesh was incorporated to create patterned surfaces, increasing surface roughness and tailoring the porous structure. The analysis included optical and scanning electron microscopy, water contact angle (WCA) measurements, Fourier transform infrared spectroscopy, electrochemical corrosion tests, and atomic force microscopy. Incorporating GNP notably increased WCA by 20–23° and reduced corrosion rates in a 3.5% NaCl solution. Likewise, applying stainless-steel mesh improved surface roughness, raising WCA by 3-8° and decreasing corrosion rates. The study observed changes in porous structure, with pore size reduction correlating with increased roughness and decreased corrosion rates upon mesh application and GNP addition. This comprehensive examination highlights the potential of PU coatings for various applications and underlines the importance of tailored porous structures in enhancing their performance and versatility. Spin coating emerged as the optimal technique, yielding uniform, defect-free coatings with the highest WCA.