Green Eugenol Oligomers as Corrosion Inhibitors for Carbon Steel in 1M HCl

Abstract This study investigated the corrosion inhibition of polyeugenol on API P110 in 1 M HCl. Its monomer – eugenol – is obtained from clove and cinnamon, making the oligomer environmentally friendly. The influence of molecular weight and polymerization degree was evaluated by increasing the polymerization initiator/monomer ratio. This enabled the polymerization of three different oligomers (P10, P20 and P30), which were characterized by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), thermogravimetric analysis (TGA/DTG), and size exclusion chromatography techniques. The inhibition performance of polyeugenol was determined by weight loss (WL) and electrochemical tests to assess the influence of structural differences. WL indicated that the oligomer with the lowest polymerization degree (P10) exhibited greater efficiency (82-84%) due to more uniform surface coverage. Electrochemical tests confirmed polyeugenol as a mixed inhibitor. Energy-dispersive X-ray spectroscopy (EDX) calculations indicated the presence of an organic layer covering the steel surface.