Enhanced steel surface protection using TiO2/MS30 modified polyurethane coatings: Synthesis and performance evaluation

Abstract

This work focuses on the development and evaluation of corrosion-resistant behavior of polyurethane (PU)-based coatings modified with TiO2 and a novel green corrosion inhibitor, 1,1′-(1,4-phenylene)bis(3-(pyridin-2-ylmethyl)urea) (MS30). Unlike conventional inhibitors, MS30 was synthesized in-house using a sustainable process involving 2-picolylamine and 1,4-phenylene diisocyanate, offering an eco-friendly alternative with superior corrosion inhibition properties. The TiO2 particles were loaded with MS30 through an overnight stirring process followed by vacuum cycling, achieving a loading efficiency of 46 % w/w as confirmed by thermogravimetric analysis (TGA). The incorporation of 1 wt% TiO2/MS30 into PU coatings, applied via the doctor blade technique on steel substrates, resulted in enhanced corrosion resistance compared to unmodified PU coatings. Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis verified the morphological and surface area changes of the synthesized particles, while Fourier transform infrared (FTIR) analysis confirmed the strong interactions between MS30 and TiO2. Differential scanning calorimetry (DSC) showed that the modified PU coatings exhibited improved thermal properties due to effective crosslinking. Tafel analysis indicated that the TiO2/MS30 modified coatings significantly outperformed existing corrosion inhibitors, reducing corrosion current density and enhancing protection. Raman analysis highlighted successful interaction between iron and MS30, contributing to superior barrier properties. Electrochemical impedance spectroscopy (EIS) demonstrated a remarkable corrosion inhibition efficiency of 99.9 % after immersion in 3.5 wt% NaCl solution, far surpassing typical commercial systems. Additionally, salt spray testing revealed that the TiO2/MS30 modified coatings sustained durability for over 4 weeks in harsh saline conditions, whereas blank PU coatings failed prematurely. The combination of high inhibition efficiency, long-term durability, and environmentally friendly synthesis, positions the TiO2/MS30 system as a superior alternative to traditional corrosion inhibitors, offering both enhanced performance and sustainability for real-world applications in challenging environments.