Aqueous extract of leaves of Morinda tinctoria as a corrosion inhibitor for aluminum in sulphuric acid medium

The corrosion inhibition of aluminum in sulphuric acid using an aqueous extract of leaves of Morinda tinctoria (MT) was studied with weight loss and electrochemical techniques. It was found that the MT extract acts as a good inhibitor for aluminum corrosion in the sulphuric acid medium. The inhibition efficiency of the inhibitor is found to increase with the increase in concentration of the acid. Synergistic effect increased the inhibition efficiency of MT in the presence of halide additives. The process of adsorption of the inhibitor on the metal surface is found to obey Freundlich isotherm. The adsorbed film on the metal surface has been analyzed by FT-IR and SEM-EDXS studies. Polarization measurements showed that MT extract is a mixed type inhibitor. Impedance results indicate adsorption of the MT on the Al surface is through charge transfer.