Corrosion inhibition performance of different bark extracts on aluminium in alkaline solution

The present work shows the effect of stem bark extracts of three trees namely Moringa oleifera (MO), Terminalia arjuna (TA) and Mangifera indica (MI) on the corrosion behaviour of Aluminium Alloy (AA) in 1 M NaOH. The inhibition performance was studied by using gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. Among these extracts, MO exhibited the maximum inhibition efficiency η (%) of 85.3% at 0.6 g/L at 303 K. Polarization measurement showed that all the examined extracts are of mixed-type inhibitors. Langmuir's adsorption isotherm was found to be best fit. Morphology of the surface was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) which confirmed the existence of a protective film of inhibitor molecule on AA surface.