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.
