Experimental and Theoretical Evaluation of Corrosion Inhibition Performance of Senna Obtusifolia Leaves Extract on Mild Steel In 0.5M HCl

Abstract

Corrosion of metal is a problem which lead to serious economic lost in industries and households, and one of the most important ways to protect metallic from being destruction (corrosion) is the use of substances (inhibitor) to protect the metal corrosion. Use of green corrosion inhibitor is found to be environmentally friendly useful compare to the use of inorganic inhibitors which are toxic. Corrosion inhibition performance and adsorption effect of Senna obtusifolia leaves (SOL) extract on mild steel in 0.5M HCl has been assessed using weight loss measurement, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), quantum chemical analysis and molecular dynamic simulations. The inhibition performance of SOL extract was found to be 85.67% %. Similarly, the result from the PDP shows SOL extract behaves as cathodic type inhibitor also from EIS it shows increase in the concentration of the extract and charge transfer resistance with decrease in double layer capacitance from the Nyquist plot. SOL extract was found to obeys Langmuir isotherm model. Furthermore, the extract was characterized using FTIR and Uv-Visible spectroscopy which confirmed the adsorption of SOL extracts on the mild steel. SEM Surface morphology of the inhibited mild steel shows the smooth surface from assuring the protection offered by the SOL extract on the metal surface. HPLC technique suggest the main component of SOL extract responsible for the inhibition performance was found to be Kaempferol molecule at 2.99 retention time. Kinetic studies revealed that the adsorption process follows first order reaction and the half-lives of inhibited metal is greater than that of uninhibited metal The results from quantum chemical calculations confirmed good inhibition performance of SOL extract and. molecular dynamic simulation shows negative values of binding energy that is less than 100 Kcalmol^-1 which suggests physical adsorption