This study investigated characterization of Epiphyllum oxypetalum (EO) leaf extracts and optimization of process variables on inhibition of mild-steel in 3 M H2SO4 aggressive environment. Response Surface Methodology (RSM) was employed to examine the influence of process variables namely acid concentration (1.0 – 3.0 mols), inhibitor concentration (0.2 – 1.0 g/l), time (1–10 hr) and temperature (303 -343K) on inhibition efficiency. The results of phytochemical screening showed that organic components present in EO extract as a good inhibitor. Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) studies established the presence of active compounds and adsorption of leaf extracts on metal surface. The experimental data was statistically analyzed and regression equations for corrosion rate and inhibition efficiency generated. The optimum conditions were achieved at acid concentration of 1.00 mol, inhibitor concentration of 0.055 g/l temperature of 333K, and time of 2.750 hr. The optimization results revealed that inhibition efficiency of 82.93 % was obtained at optimum combination of the extract concentration, the acid concentration, the temperature and the immersion time. The inhibitive potentials of EO extract was found to impede the localized and uniform corrosion of mild steel in acidic media, showing that the Epiphyllum oxypetalum leaf extract is a good inhibitor for mild steel in acidic solutions.
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