THE INHIBITORY ACTION OF THE AQUEOUS EXTRACT OF MOLTKIA CILIATA AS AN OVERPRODUCT ON THE CORROSION OF CARBON STEEL IN A SOLUTION OF 0.1N HCI

In this work, we studied the efficiency of corrosion inhibition of carbon steel XC70 in 0.1N HC1 using the aqueous extract of Moltkia ciliata. The inhibitory potency was determined by weight loss and the Potentiodynamic Polarization method. The results indicated that the inhibition efficiency increases with increasing extract concentration. A maximum inhibition rate of 76.26% in HC1 was recorded at 8 % (v/v) of inhibitor concentration according to Potentiodynamic measurements. We also studied the impact of temperature on the corrosion with non-attendance and attendance of the optimum concentration in temperature range from 298K to 363K and computed the activation energy, enthalpy, entropy, free energy and the heats of adsorption .The plant seems to be a good corrosion inhibitor of mixed mode of inhibition in the medium based on the obtained results. The adsorption on the metal surface was found to obey to Langmuir isotherm. The adsorption can be attributed to the presence of O-at-oms, 𝝿- electrons and aromatic rings found in natural compounds of the aqueous extract of Moltkia ciliata such as flavonoids, alkaloids, Sterols, Volatile oils, saponins and tannins.