Corrosion inhibition potentials of Strichnos spinosa L. on Aluminium in 0.9M HCl medium: experimental and theoretical investigations

Abstract

Aluminium is known as one of the most useful metals on earth which is also subject to corrosion under certain environments. Many methods have been used to minimize its corrosion, but the use of inhibitors is widely accepted. The use of green inhibitors has gained wide usage because of its environmental friendliness. The experimental studies of the corrosion inhibition potentials of Strichnos spinosa L was carried out using weight-loss and Fourier transform infrared spectroscopy (FTIR), whereas theoretically, quantum chemical parameters and molecular dynamic stimulations of some compounds isolated from the plant in literature were studied. The analyses of the experimental results showed that the extract of Strichnos spinosa L. extract decreased the corrosion rate of Aluminium in 0.9M HCl in the order: 0.2g/l < 0.4g/l < 0.6g/l respectively from 303-323K. The inhibition efficiency decreased with increase in temperature and was found to be 84.7%. FTIR results showed that the inhibition mechanism is physical through the functional groups present in the extract. The data obtained were fitted into various adsorption isotherms and relatively the Freundlich isotherm was found to be the best fit. Relying on quantum chemical parameters and molecular dynamic stimulations results, the adsorption/binding strength of the concerned inhibitor molecules on Aluminium surface follows the order Ursolic acid>Betulinic acid>Erythrodiol. The computed adsorption/binding energy values (Eads) for the various isolated compounds from the plant indicate the adsorption process to be non-covalent (physiosorption) which is in good agreement with the experimentally determined adsorption mechanism.