Kinetic and Thermodynamic Investigation on Mild Steel Corrosion Inhibition by Terminalia Mantaly Leaf Extract

Abstract

Mild steel (MS) corrosion inhibition by Terminalia mantaly (TM), in 1.0 M HCl, was studied using weight loss and linear polarization methods, at different reaction conditions. Gas chromatography-mass spectrometry (GC-MS) was used to determine the possible extract components. Fourier transformed infrared spectroscopy (FTIR) and optical microscopy were used to investigate the interaction of the plant extract phytochemicals with the MS surface. The obtained results revealed that the inhibition efficiency percentage (IE%) increased with a decrease in the TM concentration, and decreased with a rise in temperature (T). The IE% also decreased as the hydrochloric acid (HCl) concentration increased. Inhibition occurred through the TM phyto-molecules adsorption onto the MS surface. The corrosion inhibition kinetics followed a zero order reaction, and it was uni-molecular. The linear polarization showed that TM is a mixed-type inhibitor. Gibb’s free energies values confirmed a spontaneous process, while TM adsorption onto the MS surface was found to obey physisorption, aligning with the Langmuir’s and El-Awady’s adsorption isotherm models.