A green approach to corrosion inhibition of mild steel in hydrochloric acid using fruit rind extract of Garcinia indica (Binda)

In this study, we evaluate the efficiency of Garcinia fruit rind extract (GIW) as a green inhibitor for mild steel in HG medium. The aqueous extract is rich in cyanidin and anthocyanin pigments and their presence are detected by a peak around 520 nm in the UV-Visible spectrum and the functional groups with oxygen atoms and aromatic rings are found from the IR spectrum. The inhibition efficiency is determined by weight loss and electrochemical methods. GIW act as an effective inhibitor giving 93% efficiency in 0.5 M HCl and 87% for 1 M HCl at 303 K and 80% for 1 M HCl at 333 K. GIW act as a mixed type inhibitor and the inhibition mechanism is by monolayer adsorption of constituent molecules of GIW, which obeys Langmuir adsorption isotherm. The quantum chemical calculations on chief constituent molecules of GIW show that they can be adsorbed on the metal surface through free OH groups or pi electrons. The cyanidin molecules exist as oxonium ion in HCl and engage in back bonding with metal-cantered orbitals. (C) 2020 Elsevier B.V. All rights reserved.