ISSN 2995-9246
International Journal of Chemistry | Vol. 1, No. 3, March 2010 | pp. 18–25
DOI: 10.46882/2010/IJC/000003
Article Type: Original Research Paper
Title: Electrochemical Evaluation of Mild Steel Corrosion Inhibition in Hydrochloric Acid Solution by Azadirachta indica Leaf Extract
Names of Authors: Chinedu J. Okafor¹, Amara L. Diallo², Jean-Pierre Dupont²
Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Nigeria
²Laboratory of Materials Science, Universite de Robert Sorbonne, Paris, France
Abstract: The corrosion inhibition of mild steel in a 1.0 M HCl solution by the crude methanolic extract of Azadirachta indica (Neem) leaves was investigated using weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Weight loss experimental results indicated that inhibition efficiency increased with an increase in the concentration of the extract, reaching a maximum efficiency of 92.6% at an optimum concentration of 1000 mg/L after 24 hours of immersion at 298 K. Potentiodynamic polarization curves revealed that the extract acted primarily as a mixed-type inhibitor, retarding both anodic metal dissolution and cathodic hydrogen evolution reactions, with a slight predominant control over the cathodic reaction. EIS data showed that as the inhibitor concentration increased, the charge transfer resistance increased while the double-layer capacitance decreased, confirming the adsorption of phytochemical constituents onto the metal surface. The adsorption of the extract components on the mild steel surface obeyed the Langmuir adsorption isotherm. The calculated standard Gibbs free energy of adsorption (Delta G°ads) was -21.4 kJ/mol, indicating a spontaneous, physical adsorption mechanism. Scanning electron microscopy (SEM) surface analysis confirmed the formation of a protective organic film on the mild steel specimen, preventing acid attack.
Keywords: Corrosion inhibition, Mild steel, Azadirachta indica, Potentiodynamic polarization, EIS, Adsorption isotherm
Manuscript Timeline: Received: December 01, 2009; Revised: January 15, 2010; Accepted: February 02, 2010; Published: March 05, 2010