Corrosion Inhibiting Effect of Aframomum melegueta Extracts and Adsorption Characteristics of the Active Constituents on Mild Steel in Acidic Media

Abstract

The extract from the seeds of Aframomum Melegueta (AM) was investigated as corrosion inhibitor for mild steel in aerated 1 M HCl and 0.5 M H₂SO₄ solutions using gravimetric and electrochemical techniques. AM extract was found to inhibit both the cathodic and anodic partial reactions of the corrosion process, via adsorption of the organic matter on the metal/solution interface, as described by the Langmuir as well as Flory-Huggins adsorption isotherms. Corrosion rates in all systems studied increased with rise in temperature. Increasing the temperature of the system enhanced inhibition efficiency of AM extract in 1 M HCl, but decreased efficiency in 0.5 M H₂SO₄. Molecular dynamics simulations were performed to theoretically illustrate the electronic structure and adsorption behaviour of the active constituents of the seeds of Aframomum melegueta; paradol (1-(4-Hydroxy-3-methoxyphenyl)decan-3-one) and shogaol ((E)-1-(4-Hydroxy-3- methoxyphenyl)dec-4-en-3-one) in order to theoretically evaluate their contributions to the corrosion inhibiting action of the extract.

Keywords:

• Aframomum melegueta
• corrosion inhibition
• inhibition efficiency
• mild steel
• molecular modeling

Acknowledgments

This project is supported by TWAS, the Academy of Sciences for the developing World, under the TWAS Grants for Research Units in Developing Countries Program (TWAS-RGA08-005) and the Education Trust Fund (ETF); under batch one of ETF 2009/2010 research projects intervention for the Federal University of Technology Owerri.