Bidens aurea aiton plant extract as a green and sustainable corrosion inhibitor for carbon steel X42 in hydrochloric acidic medium: Experimental and computational studies

Abstract

The use of synthetic inhibitors, both organic and inorganic, has been severely restricted and limited because of their toxicity, high cost, complex synthesis procedures, and danger to the environment and human health. To replace the conventional harmful corrosion inhibitors, researchers have been engaged to develop green corrosion inhibitors. Plant extracts are a promising source of green corrosion inhibitors due to their non-toxicity, biodegradability, environmental friendliness nature, low cost, and natural abundance. This study aims to assess Bidens aurea aiton extract (BAA) as a potential green corrosion inhibitor for carbon steel in a 0.5 M HCl medium using weight loss, electrochemical, surface characterization, and computational chemistry methods. The results demonstrate that the BAA inhibitor behaved as an effective corrosion inhibitor with a concentration-dependent inhibition efficiency reaching a maximum of 94 %. Polarization studies indicate that the BAA acted as a mixed-type inhibitor. Electrochemical impedance spectroscopy (EIS) results revealed an increase in charge transfer resistance (R_ct) and a decrease in the values of double-layer capacitance (C_dl) in the presence of BAA. The adsorption of BBA on the metal surface follows the Langmuir isotherm. Surface analysis confirmed the formation of a protective layer of BAA on the steel surface. The density functional theory (DFT) study of the basic components present in BAA extract suggests that they interact with the metal surface through their reactive sites using the donor-acceptor mechanism.