Comprehensive evaluation of tetraglycidyldiphenylcarbazide as a corrosion inhibitor for mild steel: an electrochemical and theoretical approach

초록

In this study, tetraglycidyldiphenylcarbazide (TGDPC) was investigated using electrochemical, surface, and computational analyses as a protective agent for mild steel (MS) in 1 M HCl. Electrochemical analysis demonstrated that TGDPC acts as a mixed-type inhibitor, effectively suppressing both anodic iron dissolution and cathodic hydrogen evolution. The highest protection efficiency was 95.5% as measured by potentiodynamic polarization (PDP) and 92.27% by electrochemical impedance spectroscopy (EIS) at a concentration of 10-3 M. This corresponded to a significant decrease in corrosion current density from 4.1615 x 10-4 A/cm2 (blank) to 1.8355 x 10-5 A/cm2 at 10-3 M. Computational studies revealed that TGDPC and its protonated form (TGDPC-H+) strongly interact with Fe surfaces, facilitating effective adsorption. Density functional theory (DFT) calculations showed that TGDPC-H+ exhibited a lower energy gap (Delta Egap = 4.109 eV) compared to neutral TGDPC (Delta Egap = 4.175 eV), indicating higher chemical reactivity and adsorption efficiency. Radial distribution function (RDF) analysis further supported this, showing enhanced interaction of oxygen and nitrogen atoms with Fe (O: 6.33 & Aring;, N: 8.77 & Aring; for TGDPC-H+). The Fukui function analysis identified key nucleophilic and electrophilic sites, confirming the inhibitor's capability to donate electrons to Fe surface. Additionally, Bode and Nyquist plots demonstrated increased charge transfer resistance (Rct) from 5.799 Omega cm2 (blank) to 38.02 Omega cm2 (10-3 M), indicating enhanced surface protection. The adsorption mechanism followed the Langmuir isotherm, confirming monolayer adsorption. These findings, supported by experimental and computational analyses, validate TGDPC as a good defensive agent, with its protonated form (TGDPC-H+) exhibiting superior inhibition efficiency and surface stability in acidic environments.

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