Synthesis and characterization of novel dicarbohydrazide derivatives with electrochemical and theoretical approaches as potential corrosion inhibitors for N80 steel in a 3.5% NaCl solution

Two novel ethanoanthracene-11,12-dicarbohydrazide derivatives N'¹¹,N'¹²-bis((Z)-4-hydroxybenzylidene)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbohydrazide (H₂HEH) and N'¹¹,N'¹²-bis((Z)-4-methoxybenzylidene)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbohydrazide (H₂MEH) were synthesized and characterized by FT-IR spectroscopy, electronic spectra, and NMR spectroscopy. These two derivatives as novel anticorrosion inhibitors for N80 steel in a 3.5% NaCl solution were studied using electrochemical techniques including potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM). Corrosion parameters and adsorption isotherms were determined from current-potential diagrams (i.e., Tafel slopes). The impact of temperature and inhibitor concentration on the corrosion performance was studied using the PP method. The PP results suggested mixed-type inhibitors. The inhibition prohibition increased and decreased when the dose was increased and the temperature was increased, respectively. The adsorption of the hydrazides on the N80 exterior followed the Langmuir isotherm. The maximum inhibition proficiency for H₂MEH and H₂HEH were 93.3% and 92.2%, respectively, at 1 × 10⁻⁴ M. Moreover, the investigated surface was studied with the synthesized compounds through X-ray photoelectron spectroscopy (XPS) to confirm the construction of an adsorbed shielding barrier. An evident association was established between the corrosion inhibition proficiency and theoretical variables acquired using the density functional theory (DFT) method and Monte Carlo (MC) simulations. The experimental data were in good agreement with the theoretical results.