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 HCl 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 π electrons. The cyanidin molecules exist as oxonium ion in HCl and engage in back bonding with metal-cantered orbitals. [Display omitted] •Garcinia indica fruit rind extract (GIW) developed as an efficient inhibitor for mild steel corrosion in HCl.•The UV-Visible spectrum reveals the presence of anthocyanins responsible for the high inhibition efficiency•Efficiency decreases with temperature and the behaviour is mixed type as evident from the PDP and EIS.•The mechanism of inhibition is adsorption and which obeys Langmuir isotherm model.•Phytochemicals of the extract act as electron donors/ acceptors with MS and inhibit corrosion rate