An appropriate approach and computational studies for evaluating metal shielding features using diazenyl naphthalen analogues as sustainable corrosion inhibitors

Abstract

The current work assessed the corrosion inhibitory efficacy of three ligands, namely methyl 2-((2-hydroxynaphthalen-1-yl)diazenyl)benzoate(MDN), 1-((3,4-dimethylphenyl)diazenyl)naphthalen-2-ol (DDN), and 3-((2-hydroxynaphthalen-1-yl)diazenyl)benzonitrile (HDN). Electrochemical and quantum methodologies, along with UV-Vis, SEM, and EDX, were employed. The anticorrosion process was comprehensively investigated. Potentiodynamic polarization validated the mixed type nature of inhibitors by demonstrating a drop in the cathodic hydrogen evolution reaction and the anodic metal dissolution, resulting to a significant decrease in corrosion current densities. Enhanced rates of effectiveness are achieved with higher inhibitor doses. Electrochemical impedance spectroscopy investigations confirmed the formation of a protective layer at the metal/solution interface, demonstrating that charge transfer was the primary cause of mild steel corrosion. The inhibitory potencies of the studied inhibitors at 10-3 M were 94.65, 94.56, and 93.63% for MDN, DDN, and HDN, respectively. The presence of several attributes in the molecular skeleton, such as nitrogen heteroatoms, aromatic rings, and the ester substituent group (CO2CH3), enhanced the availability of non-bonded and pi-electrons and created stable covalent bonds by donating electrons to the iron surface. The inhibitory efficiency was better than 89% across all temperature ranges, suggesting the potential benefits of inhibitors at elevated temperatures. Adsorption trials revealed high effectiveness in corrosion control on mild steel, with Langmuir-based physisorption and chemisorption. The impact of electronegative O and N atoms, along with aromatic rings, in forming protective coatings was demonstrated by quantum chemistry computations which linked molecular structure and charge density patterns to the inhibition potency of MDN, DDN, and HDN, highlighting MDN's strong adsorption capacity.