The present study evaluated the activity of extract obtained from the peel of Fuji apples (Malus Domestica) harvested in the region of Valparaiso, Chile, as a potential corrosion inhibitor for carbon steel in a saline medium. The total phenol and flavonoid content in the extract was measured and its main components were identified using HPLC-MS. The inhibition efficiency of the extract was evaluated by mass loss measurements, Tafel polarisation curves and electrochemical impedance spectroscopy, obtaining an inhibition percentage of around 90% at a concentration of 1000 ppm of extract. Adsorption of the extract's components on the surface of the steel followed the Langmuir adsorption isotherm model, implying a physisorption mechanism based on thermodynamic parameters and from the ΔG 0 ads value, which was calculated at -15.16 KJ/mol. SEM was used to verify the presence of an organic layer on the steel, corroborating the adsorption of the organic components from the extract blocking active sites on the steel.
In the present study, the activity of extracts obtained from the stems of two endemic species of the central–northern region of Chile (Eulychnia acida [Copao] and Echinopsis chiloensis [Quisco]), was evaluated as potential corrosion inhibitors for carbon steel in 0.1 M HCl. The total content of phenols and flavonoids in the extracts was determined, and the main components were identified by high‐performance liquid chromatography–mass spectrometry, being similar in both species. The inhibition efficiency of extracts was evaluated by mass loss measures, Tafel polarization curves, and electrochemical impedance spectroscopy. The assay results showed similar values in inhibition percentages, around 88% at extract concentrations of 1,500 ppm. The adsorption on the steel surface followed the Langmuir model adsorption isotherm, whose thermodynamic parameters (ΔG°ads for Copao and Quisco, −17.81 and −17.70 kJ/mol, respectively) suggest a physisorption mechanism. The scanning electron microscopy analyses showed that in the presence of the extracts, the surface of the steel is covered by a thin film that allows the sanding marks to be visualized; while without the extracts the surface is rough due to the HCl corrosion effect.
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