Thermodynamics, Adsorption and Spectral Studies of the Corrosion Inhibition of Mild Steel by Different Leaf Extracts in 1.0N HCl : Comparative Analysis

The present study investigated the inhibition effect of leaf extract of Tephrosia Purpurea (T. purpurea) and Pongamia pinnata (P.pinnata) on mild steel corrosion in 1N HCl solution using gravimetric methods with different varying parameters such as inhibitor concentration, immersion time and temperature. Characterization of leaf extract of T. purpurea was carried out using UV- visible spectroscopy (UV-Vis), Fourier-Transform Infrared Spectroscopy (FTIR). From the results, it was found that, the inhibition efficiency (I.E in %) increases with increase in concentration of the inhibitor molecules and the maximum inhibition efficiency of 93(%) was observed at 300ppm of the leaf extract. And, it was found that, the adsorption of inhibitor molecules obey Langmuir, Temkin, Freundlich adsorption isotherms. The inhibition is mainly attributed to the adsorption of inhibitor molecules on the mild steel electrode surface. Kinetic as well as thermodynamic parameters calculated, also confirmed the strong interaction between inhibitor molecules and the electrode surface. Scanning Electron Microscope (SEM) experiments also confirmed the presence of inhibitor molecules on the mild steel surface. From all these experimental results, it can be concluded that, the leaf extract of T.purpurea and P.pinnata acted as a good corrosion inhibitor for mild steel in 1N HCl medium.