Improved carbon steel corrosion characteristics in static and hydrodynamic HCl media by two novel N2O2 ligands: Experimental and theoretical studies

Background: Expanding the use of carbon steel in various industrial operations is always associated with chal-lenges due to many engineering factors in the selection of materials. However, carbon-steel corrosion is a sig-nificant challenge in many industries, particularly the oil and gas sector.Methods: This study created and employed two novel N2O2 ligands to prevent simple carbon steel from corroding in static and dynamic hydrochloric acid solutions. Corrosion tests were performed in none, 50, 100, and 250 ppm of the new compounds. Therefore, immersion, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests were used to investigate the anti-corrosion effect. In addition, the impact of hydrodynamic conditions on performing the inhibitors was also conducted. The B3LYP (Becke, 3-parameter, Lee-Yang-Parr), HF (Hartree-Fock), M062X approach with 6-31++G(d,p) basis sets was employed using the Gaussian software to study the inhibitory activities of molecules in the gas and water phases.Significant findings: According to the PDP test, there is a direct correlation between the amount of inhibitor and resistance to corrosion in static conditions, where the reduced ligand was more efficient. The EIS data revealed that, in a 1.0 M HCl solution with an inhibitor concentration of 250 ppm, the ligand and its reduced form enhanced corrosion resistance by 86.38% and 91.43%. Furthermore, these values were found to be 33.46% and 57.77%, in turbulent environment of 500 rpm. The atomic force microscopy (AFM) studies revealed that the ligand and its reduced form decreased surface roughness by 13.61% and 85.37% in static conditions and 59.67% and 61.53% in a hydrodynamic environment in comparison to 1.0 M HCl solution. Additionally, the UV test demonstrated that the amounts of iron corrosion was less severe in H2L2 than in H2L1 and 1.0 M HCl. Under static and dynamic conditions, the samples had lower specific weight changes during the immersion test, indi-cating that the inhibitory chemicals protected the samples' surfaces. Both compounds followed the Langmuir adsorption process. Furthermore, quantum chemical parameters simulations indicate the compounds' anti-corrosive abilities.

Automated summary

This study developed two new N2O2 ligands that effectively prevent carbon steel corrosion in static and dynamic hydrochloric acid solutions. Corrosion tests showed that the concentration of the ligands directly affected the corrosion resistance, with the reduced form exhibiting better inhibitory effects. The study also investigated the impact of hydrodynamic conditions on the performance of the inhibitors.