Green corrosion inhibition and adsorption characteristics of Luffa cylindrica leaf extract on mild steel in hydrochloric acid environment

Abstract The corrosion inhibition of Luffa cylindrica Leaf Extract (LCLE) was investigated using gravimetric, depth of attack and surface analysis techniques. Effect of inhibitor concentrations (0.50–1.00 g/l), temperatures (30–60 °C) and immersion time (4–12 h) was studied on the Inhibition Efficiency (IE) of the extract on Mild Steel (MS) immersed in a 0.5 M HCl solution. The constituents of the proposed inhibitor were identified by using a GC-MS. The media solutions and adsorbed film on MS were characterized using FTIR Spectrophotometer. SEM microgram and surface tester were applied for studying surface morphology and depth of attack profile. The optimum IE of 87.89% was obtained. The LCLE adsorption on MS followed Langmuir isotherm and pseudo-second-order adsorption kinetics. Activation energy (28.71 kJ/mol), entropy (- 0.15 kJ/mol. K), average enthalpy (-28.00 kJ/mol) and Gibbs free energy (-11.43 kJ/mol) obtained at optimum condition indicate exothermic process and physical adsorption mechanism. The result obtained in this study compared well with many reported green inhibitors for MS corrosion.