Carissa macrocarpa extract (ECM) as a new efficient and ecologically friendly corrosion inhibitor for copper in nitric acid: Experimental and theoretical approach

•Carissa macrocarpa leaf extract (ECM) has an inhibition efficiency above 90%.•The findings indicate the bonding information between the main components of ECM and copper surface.•ECM act as a cathodic character.•Deep insights into the inhibitory process are provided by computational calculations. To prevent metals from corroding faster, corrosion inhibitors form in the environmental medium and emerge at the right concentrations. The current inhibitors on the market have certain shortcomings. It is therefore necessary to find a new type of corrosion inhibitor that is cheaper, ecofriendly and effectively prevents corrosion. In this work, an efficient and eco-friendly Carissa macrocarpa leaf extract (ECM) was investigated by weight loss and electrochemical measurement, subsequently; the surface morphology of copper treated with HNO3(with and without ECM) was characterized by SEM coupled with EDS and FTIR Analysis. In order to explore the adsorption potential and the reactive atomic regions of organic compounds in ECM, extensive theoretical explorations at electronic and atomic levels were carried out using electronic-structure density functional theory (DFT) and Monte Carlo (MC). The experimental findings demonstrate the cathodic type inhibitory properties of the ECM, and the corrosion inhibition effect is above 91%. The mechanism of inhibition of Cu by ECM is described in detail. Furthermore, the ECM extract has good inhibitory efficiency over a broad temperature range, from 298 to 333 K. The computed thermodynamic parameters revealed that the extract's adsorb on the copper surface was spontaneous and under physico-chemical processes control. In addition, it is found that the activation complex is formed by the binding of Cu+ and ECM in the adsorption layer. Molecular modeling highly asserted the preference of the ECM extract molecules for adsorption onto the copper surface and DFT explorations emphasized that oxygen heteroatoms behaved as relevant local sites for molecular adsorption. [Display omitted]