Bio-Based Eugenol-Derived Azo Pigments: Synthesis, Characterization, and Corrosion Protection Performance in Epoxy Coatings

The increasing demand for sustainable and renewable alternatives to petroleum-based raw materials in pigment synthesis has encouraged the exploration of naturally occurring bio-based compounds. In the present study, eugenol, a naturally occurring phenolic compound derived from plant sources, was utilized as a coupling component for the synthesis of azo pigments through diazotization and azo-coupling reactions. Five structurally different azo pigments were successfully synthesized and comprehensively characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) to evaluate their chemical structure, thermal stability, and surface morphology. The synthesized pigments were subsequently incorporated individually into epoxy coating formulations at pigment loadings of 0.5, 1, 5, and 10 wt% to investigate their suitability as environmentally friendly anticorrosive pigments. The performance of the pigmented epoxy coatings was assessed through electrochemical impedance spectroscopy (EIS), corrosion resistance testing, and mechanical property evaluations. In addition, the antimicrobial activity of the pigment-containing coatings was examined to determine their potential for multifunctional protective applications. The results demonstrate that eugenol-derived azo pigments exhibit excellent compatibility with epoxy coatings and significantly influence the coatings' corrosion protection, mechanical performance, and antimicrobial properties, highlighting their potential as sustainable bio-based pigments for advanced protective coating applications. The study gives a sustanable alternative to the antimicrobial coating from naturally derived sources.