The inhibitive performance of Sapium ellipticum leaf extract as green corrosion inhibitor for carbon steel in varying concentrations in hydrochloric acid has been investigated. To determine the adsorption strength and phenomenon of inhibition, density functional theory was adopted to model the molecular structure of the extract. Also to evaluate the inhibition efficiency weight loss, electrochemical method and statistical modelling was employed. Optimum inhibition efficiency of 89 % was achieved from electrochemical study at conditions of 1.5 g L-1 SE concentration, temperature of 303 K and 1 M HCl, respectively. The electrochemical study signifies that the phenomenon of inhibition is under mixed control and the inhibition process is in accordance with Langmuir isotherm. Fourier transform infrared spectroscopy (FTIR) of the corrosion particles and surface examination (SEM) confirms the existence of the protective film on the metal surface through the adsorption of extract species.

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