Employing Cymbopogon citratus (Lemongrass) as eco-friendly corrosion inhibitor for mild steel in seawater

Cymbopogon citratus (lemongrass) is a common plant in Southeast Asia that is rich in phytochemical compounds, such as flavonoids, phenolics and tannins. These compounds play an essential role in corrosion-inhibition processes. The characterization of the extract was done by Fourier Transform Infrared and UV-Vis Spectroscopy. The anticorrosion action of lemongrass extract was evaluated for mild steel through immersion in seawater medium using weight-loss and Electrochemical Impedence Spectroscopy. The surface analysis was carried out by optical and Scanning Electron Microscope. The mild steel grade JR235 was prepared in size of 25 mm × 25 mm × 3 mm and was polished using a stand grinder. The immersion test was conducted in seawater with different concentrations of lemongrass extract for a duration of 50 days. Meanwhile, the amount of lemongrass extract incorporated varied from 5%, 10%, 15% to 20%. Six characterizations were conducted in this study which are weight-loss study, Fourier Transform Infrared, UV-Vis spectroscopy, Electrochemical Impedance Spectroscopy, Optical Microscope and Scanning Electron Microscope. In this study, a major constituent recorded was lawsone, which can impede corrosion on metal surfaces. The results indicated that weight loss without additive was higher compared to other samples with additives. The weight-loss results show that 10% and 20% additive managed to reduce corrosion by 0.07104% and 0.16234% compared to without additives, respectively. Charge transfer resistance increases up to 3.2x10⁶ Ω.cm² with the presence of 20% additive. Surface studies results reveal that additives significantly improve the smoothness of the mild steel surface. Thus, this study finds that lemongrass is a potential functional natural additive for steel, particularly mild steel in seawater medium.