Evaluation of Morinda citrifolia extract as sustainable inhibitor for mild steel in saline environment

In this study, the Morinda citrifolia extract was evaluated as a sustainable inhibitor of mild steel in saline environments. The work aimed to determine the inhibition efficiency of new active material for metal corrosion inhibition. The powdered simplicia of M. citrifolia was extracted in the macerator for three days using a solvent daily. The functional group bonds of this extract were analyzed by Fourier Transform Infrared (FT-IR). The performance of M. citrifolia extracts was evaluated with potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques using a three-electrode cell system. The surface morphology of mild steel was pictured by Field effect scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Potentiodynamic polarization results show decreasing corrosion current (I_corr) with the presence of an extract of M. citrifolia. Furthermore, resistance capacity transfer (Rct) increases with the addition of M. citrifolia extract. The optimum inhibition efficiency (%IE) was achieved at 300 mg L⁻¹ concentrations with 85.10% efficiency by using the PDP technique. The mild steel morphology in the addition of M. citrifolia extracts is smoother than the surface without adding extracts. The increase in corrosion inhibition was associated with the molecule adsorption from the active compounds into the steel surface. The study results confirmed that M. citrifolia is a potential biomaterial engineering for corrosion inhibitors on mild steel in a saline environment.