Investigation on corrosion inhibition behaviour of aqueous extract of leaves of Morinda Tinctoria on Aluminium in Sodium hydroxide

The effect of aqueous extract of leaves of Morinda tinctoria on the corrosion inhibition of aluminium in alkaline medium was studied by weight loss and electrochemical methods such as electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The change in different parameters like concentrations of inhibitor, sodium hydroxide, halide ions, temperatures and immersion time was carried out to determine the longevity and stability of the inhibitor. Increase in the immersion time, alkaline concentration and temperature increases the inhibition efficiency. Investigation of temperature studies reveals that the inhibitor follows chemisorption behaviour towards corrosion protection. Temkin adsorption isotherm was obeyed throughout the corrosion inhibition process. The added halide additives produced tremendous changes in the inhibition system. The recorded scanning electron microscopy for the aluminium metal before and after the addition of inhibitor in the alkaline medium confirmed the adsorption of inhibitor molecules on the metal surface. The investigation proves that the inhibitor works perfectly against the corrosion of metal and suitable for corrosion inhibition process. Graphic Abstract