Synthesis and characterization of an effective green corrosion inhibitive hybrid pigment based on zinc acetate-Cichorium intybus L leaves extract (ZnA-CIL.L): Electrochemical investigations on the synergistic corrosion inhibition of mild steel in aqueous chloride solutions

Abstract

Mild steel structures are widely used in many applications ranging from oil and gas pipelines to cooling water system and storage tanks. The search for highly effective inhibitors based on sustainable and environmentally friendly compounds for the protection of steel in corrosive environments i.e marine condition, has attracted considerable attention and interest of researchers.In this study a new generation of corrosion inhibitive pigment based on zinc acetate-Cichorium intybus L leaf extract (ZnA-CIL.L) has been synthesized and characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), UV–visible analysis and thermal gravimetric analysis (TGA). Then, the corrosion inhibition performance of the ZnA-CIL.L hybrid pigment was studied by open circuit potential (OCP) measurements, electrochemical impedance spectroscopy (EIS) and polarization studies in 3.5 wt% NaCl solution on mild steel substrate. The surface morphology and chemistry of the steel panels dipped in the solutions without and with ZnA-CIL.L pigment extract was studied by SEM/EDS and FT-IR analyses. Results obtained from XPS, SEM/EDS, FT-IR, TGA and UV–visible analyses confirmed the successful complex formation of ZnA-CIL.L. The CIL.L extract consists of many corrosion inhibitive molecules i.e Flavone, Caffeic acid and Chicoric acid, that are full of electron-rich groups with high capability of sharing their lone pairs with Zn2+ cations, that have empty 3d orbital. Results obtained from OCP, EIS and polarization tests confirmed that the ZnA-CIL.L hybrid pigment, in its extract form in saline solution, could remarkably retard the steel sample from corrosion. Due to the synergistic effect between CIL.L and Zn2+ cations both the anodic and cathodic reactions were noticeably suppressed and inhibited in the presence of ZnA-CIL.L extract. The CIL.L molecules adsorption on the anodic sites occurred through chelation with zinc/iron cations, and the zinc cations deposited on the cathodic sites in the form of zinc hydroxide, providing proper inhibition performance for this hybrid green corrosion inhibitive pigment.