Green Approach to Corrosion Inhibition by Black Pepper Extract in Hydrochloric Acid Solution

Abstract

In the present work the corrosion inhibition of mild steel in hydrochloric solution by Black pepper extract (Piper nigrum fem. Piperaceae) was studied. The techniques employed for study were mass loss measurements, poten- tiodynamic polarisation, linear polarization resistance and electrochemical impedance spectroscopy (EIS). The results ob- tained revealed that Black pepper extract was a good corrosion inhibitor for mild steel in hydrochloric acid medium and maximum inhibition efficiency (98%) was found at 120 ppm at 35 oC. Potentiodynamic polarization curves showed that black pepper extract is a mixed-type inhibitor. EIS showed that the charge transfer controls the corrosion process in inhib- ited solutions. Adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm. The value of the free energy of adsorption, � Gads, indicated that the adsorption of inhibitor molecules was typical of chemisorption. The results obtained show that the Black pepper extract which mainly contains alkaloid 'Piperine' could serve as an excel- lent green inhibitor for corrosion of mild steel in acid solutions.