Inhibitory Potentials of Leaf Extract of Justicia schimperi for Mild Steel Corrosion in Hydrochloric Acid Medium: Gravimetric, Microscopic and Spectroscopic Studies
Msenhemba M. Mchihi *
Yaba College of Technology, Lagos, Nigeria.
Mathew C. Emesiani
Chukwuemeka Odumegwu Ojukwu University, Anambra State, Nigeria.
Juliet I. Babawumi
University of Ibadan, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Inhibitory capacity of aqueous leaf extract of Justicia schimperi (JS) for corrosion of low Carbon steel (CS) in 1 M HCl was probed using gravimetric measurements, scanning electron microscopy (SEM) and atomic absorption spectroscopy (AAS). The study was carried out in the absence and presence of different concentrations of the inhibitor in the temperature range of 303 K – 343 K. Results obtained from gravimetric analysis revealed that JS demonstrated good corrosion inhibitive performance as it considerably reduced corrosion rate of CS, achieving 86.79 % inhibition efficiency at 303 K. Percentage inhibition efficiency of JS increased with increase in concentration but decreased with increase in temperature. The adsorption of the extract on the metal surface was by physisorption and chemisorption based on values of change in Gibb’s free enery (ΔGads). The adsorption of JS on CS surface obeyed Langmuir adsorption isotherm. SEM micrographs revealed less CS surface damage in the presence of JS which indicated formation of protective inhibitor film on the surface of CS. Result of AAS analysis revealed that ferrous ion concentration in corrosive medium decreased with increase in JS concentration.
Keywords: Tassel, Corrosion, Wood, inhibition efficiency, Seeding,, Justicia schimperi, epigeal germination, low carbon steel, adsorption