Thermodynamic Studies for the Corrosion Inhibition of Mild Steel by Tectona
Grandis Leaves

N.Kasthuri[1], M.Priya[2]
Page No. 1-11

The corrosion inhibition of mild steel in 1 M HCl solution in the presence of Tectona Grandis
Leaves (TGL) at temperature range of 30–700C was studied using weight loss and electrochemical
methods namely potentiodynamic polarization and AC impedence method. The Tectona Grandis
Leaves acts as an inhibitor in the acid environment. The inhibition efficiency (90.26%) increases
with increase in inhibitor concentration (2.5%) but decreases with an increase in temperature. The
inhibitive effect of the Tectona Grandis Leaves could be attributed to the presence of some
phytochemical constituents in the Leaves which is adsorbed on the surface of the mild steel metal.
The inhibition by Tectona Grandis Leaves was found to obey Langmuir, Frenudlich, Temkin
adsorption isotherms. Phenomenon of physical adsorption is proposed from the activation
parameters obtained. Polarization curves revealed that this inhibitor acta as a mixed type inhibitor.
Thermodynamic parameters reveal that the adsorption process is spontaneous. The surface analysis
study conforms the corrosion of mild steel and its inhibition by the inhibitor TGL.
Key Words: Tectona Grandis Leaves(TGL), Mild steel, Adsorption isotherm, Thermodynamic
parameters.