Inhibitive action of the acid extract of Luffa aegyptiaca leaves on the corrosion of mild steel in acidic medium

Abstract

The inhibitive effect of the acid extract of Luffa aegyptiaca (LA) leaves on the corrosion of mild steel (MS) in the hydrochloric acid medium was studied using mass loss, colorimetric and electrochemical methods. The inhibition efficiency, increased with increase in concentration of the extract, but decreased with a raise in temperature and increase in acid strength. Polarization measurement studies revealed that LA extract act as a mixed-type inhibitor but predominantly control the anodic reaction. Furthermore, the inhibition efficiency synergistically increased with the addition of halide ions. Physical adsorption mechanism is proposed from the trend in inhibition efficiency with the change in temperature and from thermodynamic parameters. It has been found that the adsorption of LA on MS complies with Langmuir adsorption isotherm and follows the kinetic thermodynamic model of El-Awady at all temperatures studied. Fourier transform infrared spectroscopy and optical profiler images confirmed the adsorption of LA on MS surface.

Keywords:

• electrochemistry
• high temperature
• surface analysis
• FTIR
• profilometry

Acknowledgements

The authors acknowledge the services of Vergenta Electronic, LLP Demo centre, Bangaluru for their instrumental facilities.