Novel sulfur epoxy-based protection of aluminum alloy in marine conditions: a combined electrochemical and computational study

초록

Aluminum alloy 2024-T3 is widely used in aerospace and marine applications due to its excellent mechanical properties, but its susceptibility to corrosion in chloride-rich environments presents a major challenge to its long-term durability. This study looks at how well bisphenol S tetraglycidyl ether dianiline dipropoxy (TGEDADPDS) epoxy resin protects AA2024-T3 aluminum alloy when it is placed in a 3.5% NaCl solution, using both experiments and theoretical methods. Tests showed that TGEDADPDS is a very effective corrosion blocker, working better at higher amounts, reaching a maximum protection level of 95.8% when used at a concentration of 10-3 M, and reducing the corrosion current density from 23 to 1.2 mu A/cm2. Electrochemical impedance spectroscopy (EIS) results corroborated these findings, showing a significant increase in polarization resistance from 870 to 16,223 Omega cm2. Temperature dependence studies revealed a moderate reduction in inhibition efficiency at higher temperatures, retaining 88% efficiency at 328 K. Thermodynamic assessments indicated increased activation energy (from 22 to 44.73 kJ/mol) and enthalpy (from 19.4 to 42.13 kJ/mol), along with a decrease in entropy, suggesting the formation of a more ordered inhibitor-metal interface. Adsorption behavior followed the Langmuir isotherm (R2 = 1), indicating spontaneous, monolayer adsorption with a free energy of adsorption (Delta Gads degrees$\Delta {\text{G}}_{\text{ads}}{<}^{>}{<}^{>}\circ$) of - 45.25 kJ/mol. Density functional theory (DFT) calculations demonstrated favorable electronic properties of TGEDADPDS, while Monte Carlo (MC) simulations revealed a strong adsorption energy (- 276.15 kcal/mol). Scanning electron microscopy/ Energy dispersive X-ray spectroscopy (SEM/EDS) analyses confirmed smoother surface morphology and reduced corrosive element content after treatment. Collectively, these results underscore TGEDADPDS's potential as an effective, thermally stable, and surface-active corrosion inhibitor suitable for protecting aluminum alloys in marine environments.

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