Paper No. MCI42 NIGIS * CORCON 2017 * 17-20 September * Mumbai, India Copyright 2017 by NIGIS. The material presented and the views expressed in this paper are solely those of the author(s) and do not necessarily by NIGIS. Synergistic effect of l-proline mixed with sodium benzoate as sustainable corrosion inhibitor for mild steel in 1M HCl: Experimental and theoretical studies Mosarrat Parveen Corrosion Research Laboratory, Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh, 202002-India email id: mosarrat7parveen@gmail.com Mohammad Mobin Corrosion Research Laboratory, Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh, 202002-India ABSTRACT Inhibition effect of L-proline (LPr) and LPr mixed with sodium benzoate (Lpr + NaBenz) on mild steel (MS) corrosion in 1M HCl at temperature 30  C was studied employing gravimetric method, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization measurements and scanning electron microscopy (SEM). The concentration of Lpr was varied between 100-600 ppm. LPr inhibited the corrosion rate of MS at a considerable extent. Inhibition efficiency of LPr was synergistically enhanced on adding NaBenz at all concentrations. The change in impedance parameters indicated that LPr and Lpr+NaBenz molecules acted by adsorption at the MS/solution interface. Typically different surface morphologies for uninhibited and inhibited MS specimens verified the formation of adsorbed protective covering the MS surface. LPr alone and in combination with NaBenz acted as mixed type inhibitor and adsorbed on the MS surface in accordance with the Langmuir adsorption isotherm. Keywords: Mild Steel; Corrosion Inhibition; L-proline; Sodium Benzoate; Synergistic effect;