Improving corrosion inhibition of steel using polyurethane based composite coatings by incorporating zirconia nanoparticles and novel urea-based inhibitor

Abstract

Corrosion of steel in aggressive environments poses a major threat to structural integrity and operational efficiency across various industries. To address this, the present study introduces a novel polyurethane (PU)-based composite coating reinforced with zirconia (ZrO₂) nanoparticles integrated with an in-house synthesized urea-based organic corrosion inhibitor, 1,1′-(methylenebis(4,1-phenylene))bis(3-(pyridin-2-ylmethyl)urea) (MS31). This multifunctional coating system leverages the mechanical durability of PU, the barrier-enhancing role of ZrO₂ nanoparticles, and the smart, pH-responsive release characteristics of MS31 to provide active and passive corrosion protection. The composite coatings were applied to steel substrates and evaluated under simulated saline conditions (3.5 wt% NaCl). Characterization techniques including FTIR, TGA, UV–Vis spectroscopy, and contact angle measurements confirmed the successful integration of MS31, thermal stability up to 800 °C, pH-triggered inhibitor release, and hydrophobic surface behavior. Adhesion testing further demonstrated improved mechanical interlocking with the steel surface. Electrochemical analyses, including Tafel polarization and electrochemical impedance spectroscopy (EIS), revealed significantly enhanced corrosion protection relative to unmodified PU coatings, while salt spray testing validated long-term performance under corrosive exposure. This work demonstrates a robust and environmentally adaptive coating system that combines physical barrier properties with active corrosion inhibition. The integration of MS31-loaded ZrO₂ nanoparticles into the PU matrix not only improves the structural and protective features of the coating but also introduces a smart, responsive mechanism for corrosion control. These findings offer a promising pathway toward the development of sustainable, high-performance coatings for steel protection in harsh environments.