Corrosion inhibition and adsorption behaviour of black pepper extract on pure aluminum in hydrochloric acid medium

Abstract

Purpose – The purpose of this paper is to investigate the inhibitive properties of black pepper extract (BPE) for aluminium in 1M hydrochloric acid (HCl) medium. Design/methodology/approach – Gravimetric, electrochemical impedance spectroscopy, galvanostatic polarization, scanning electron microscopy with energy dispersive X-ray examinations (SEM-EDX) techniques were used to study the corrosion inhibitive study. Findings – The gravimetric measurement indicates that inhibition efficiency shows direct proportional relation with concentration of inhibitor. The impedance results illustrates that there was a presence of protective layer of inhibitor adsorbed on the metal/solution interface. Polarization outcome showed that BPE is mixed type inhibitor. The existence of adherent layer of inhibitor on the Al surface was confirmed by SEM-EDX. Quantum chemical calculations were performed using the density functional theory at B3LYP/6-31G(d) level of theory to evaluate the activity of inhibitor molecules present in extract towards the corrosion inhibition of Al. Research limitations/implications – Due to the presence of large number of compounds in the extract, it becomes difficult to understand the most active compound responsible for inhibition. However, from gas chromatography mass spectrometry and quantum data, the approximation has been made that the major compound piperine present in the extract can be most probable component responsible for the inhibition activity. Further calculation of binding energy between Al and inhibitor molecules can be performed using Material Studio software. Practical implications – The extract can be used in cleaning and etching solutions. It can be used to limit the loss of Al metal during etching process. Originality/value – BPE can be used as a potential source of eco-friendly corrosion inhibitor for Al in HCl medium.