Synthesis, electrochemical evaluation and theoretical study of new carbohydrate-derived triazoles as corrosion inhibitors for API 5L X70 steel in 1M HCl aqueous solution
Academic Article in Scopus
The organic inhibitors a) allofuranosyl-triazole-theophylline-4 (ATT4), b) glucofuranosyl-triazole-theophylline-5 (GTT5), c) allofuranosyl-triazole-theobromine-6 (ATT6), and d) glucofuranosyl-triazole-theobromine-7 (GTT7) were systematically evaluated as novel corrosion inhibitors for API 5 L X70 steel in 1 M HCl under static conditions , with the aim of assessing their potential application in the oil industry. These compounds, derived from theophylline and theobromine moieties, were selected due to their molecular structure rich in heteroatoms and ¿-electrons, which favor strong interactions with the metallic surface. The corrosion protection performance of the inhibitors was determined through electrochemical techniques , including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization curves (PDP) . The results show that, at 10 ppm, ATT4 exhibited the highest inhibition efficiency (91.4 %), followed by ATT6 (89.1 %), GTT7 (87.9 %), and GTT5 (75.3 %). The corrosion inhibition performance strongly depends on immersion time. Among the studied compounds, GTT-7 exhibits superior long-term stability, maintaining effective surface protection and achieving an inhibition efficiency of 89 % after 72 h, whereas the other inhibitors show a significant decline in efficiency due to rapid desorption from the metal surface. The electrochemical results demonstrated that all inhibitors significantly enhanced the corrosion resistance of API 5 L X70 steel by adsorbing onto the metal surface and forming a compact and protective monolayer , with adsorption behavior well described by the Langmuir isotherm model. Thermodynamic and electrochemical analyses indicated that the inhibition mechanism involves a synergistic combination of chemisorption and physisorption processes for the GTT5 and ATT6 inhibitors, whereas ATT4 and GTT7 exhibit a predominantly chemisorption-controlled mechanism. To elucidate the adsorption mechanism at the molecular level, dispersion-corrected density functional theory (DFT-D) calculations were performed. The theoretical results revealed that the theobromine and theophylline moieties act as the preferential interaction sites , promoting strong chemisorptive bonding with the steel surface. Furthermore, charge transfer from the organic inhibitors to the metal was confirmed through electrostatic potential mapping and natural bond orbital (NBO) analysis , supporting the experimental findings and highlighting the effectiveness of these compounds as corrosion inhibitors for acidic environments relevant to the oil industry.
