A comparative density functional theory (DFT) and molecular dynamics study on Natamycin and Cefmetazole as effective corrosion inhibitor for mild steel: Electronic properties and adsorption behavior

Abstract

This work investigated the corrosion inhibition mechanism of Natamycin and Cefmetazole on mild steel using Density Functional Theory (DFT) and Molecular Dynamic (MD) simulation. Natamycin exhibited a low HOMO-LUMO energy gap of 0.5 eV and a high adsorption energy of −92.7 kJ/mol which demonstrates its high chemical reactivity for effective adsorption on metal surfaces. The presence of hydroxyl groups and conjugated double bonds in its structure allows for fast electron exchange to generate strongly adhesive protective films. Cefmetazole with HOMO-LUMO gap of 2.45 eV and adsorption energy of −67 kJ/mol with β-lactam and sulfur on the adsorbent surface providing strong hydrogen bonding with the metal atoms. The independence of the generated geometries is additionally supported through MD simulations showing their adsorption configurations when providing the optimal spreading and orientation to block corrosive agents. Natamycin reacted more readily and adsorbed spontaneously, showing its suitability for use in acidic media, whereas, Cefmetazole, in contrast, affords an even inhibition profile, though only of moderate chemical stability. The conclusions also show dispositions of pharmaceutical compounds that may be used as green corrosion inhibitors which comply with the green chemistry roadmap.