Olive leaf extract as a green corrosion inhibitor of reinforced concrete contaminated with seawater

Abstract In reinforced concrete, a high alkaline medium, steel is commonly protected by formation a passive oxide film. Nevertheless, contamination with chlorides or carbonation causes the deterioration of protective film and the initiation of pitting corrosion. Hence, the need to enrich the fresh concrete solution with a good corrosion inhibitor. In accordance with green chemistry to evade toxicity and minimize waste, we have chosen to replace the usual inhibitors with an alternative not only ecological but also derived from biological wastes, in a perspective of circular economy emphasizing that waste can offer important compounds at an affordable price and easily available. In this context this work seeks to valorize the dried olive leaves extract as an inhibitor in alkaline chloride solution (pH 13). The targeted plant was grown in arid zones of Saudi Arabia and their leaves are usually disposed of as solid waste or animal feed. Four extraction solvents of different polarities were used; methanol, ethyl acetate, dichloromethane and hexane. The anticorrosive activity was performed using different electrochemical techniques; polarization curves, electrochemical impedance spectroscopy and Mott-Schottky analyses. The polarization studies proved that extract from olive leaves is a mixed type inhibitor in a solution of NaOH (0.1 M) + NaCl (0.5 M),with a predominant anodic effectiveness. The best inhibition of 91.9% is provided with methanol extract. GC–MS analysis showed the presence of compounds containing the heteroatoms N and O with the π electrons which are responsible for the corrosion inhibition activity. The olive leaves have been found to be high in phenol and flavonoid content. Inhibition efficiency of the olive leaves extracts increases with the polarity of extraction solvents but also it appears that it depends on another factors.