Alstonia Scholaris bark as an environmentally benign corrosion inhibitor for aluminium alloy in sodium hydroxide solution

Inhibition effect of aqueous extract of alstonia scholaris bark (asb) on the corrosion of aluminium alloy (aa) in 1m naoh was carried out using gravimetric,electrochemical impedance spectroscopy (eis),potentiodynamic polarization (pdp) and linear polarization resistance (lpr) techniques. asb showed maximum inhibition efficiency (η %) of 92.6% at 2.0 g/l. the adsorption of inhibitor molecules on aa surface obeyed the langmuir's adsorption isotherm. tafel polarization study showed mixed mode of corrosion inhibition of inhibitor. the effective protection of aa in inhibited system was investigated using scanning electron microscopy (sem) and atomic force microscopy (afm).