Journal
JOURNAL OF MOLECULAR STRUCTURE
Volume 1183, Issue -, Pages 168-181Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.molstruc.2018.12.035
Keywords
Mycophenolic acid; Inhibitor; EIS; 1018 steel; DFT calculations
Categories
Funding
- Facultad de Quimica within the PAIP
- SNI (Sistema Nacional de Investigadores)
- Facultad de Quimica (UNAM) at the Departamento de Ingenieria Metalurgica
- CONACyT
- DGAPA-UNAM [PAPITT IN-114619]
- Facultad de Quimica under the PAIP-FQ program
- Direccion General de Computo y de Tecnologias de la Informacion (DGTIC-UNAM) [LANCAD-UNAM-DGTIC-063]
- Direccion General de Asuntos del Personal Academico (DGAPA)
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Mycophenolic acid (IUPAC name: (E)-6-(4-hydroxy-6-methoxy-7-methyl-3-oxo-1H-2-benzofuran-5-yl)-4-methylhex-4-enoic acid) is extracted from the fungus Penicillium brevicompactum. In this work, corrosion inhibition under static conditions and turbulent flow was tested in a 3% wt. NaCl solution by means of two techniques: electrochemical impedance spectroscopy (EIS) and polarization curves. The efficiency results showed that low concentrations of mycophenolic acid are effective in static conditions, staying practically constant when the concentration of the compound is increased, with eta = 90%. The adsorption process is chemisorption at 0 rpm, while for 100 and 1000 rpm, it is a combined process. SEMEDS confirmed the decrease of the corrosion products in the presence of mycophenolic acid. These results revealed that mycophenolic acid is a good corrosion inhibitor when applied to carbon steel. To obtain insight into this behavior, the interaction between mycophenolic acid (MA) and a steel surface, modeled by a cluster of iron atoms (Fe-6), was studied using density functional theory calculations. The calculated MA-Fe-6-cluster binding free energy agrees with the experimental results and falls in the chemisorption regime. Using the reactivity Fukui indices, we demonstrated that the metal surface is completely passivated by the inhibitor, which is less reactive to different kind of attacks. After adsorption of the inhibitor molecule, the properties of the iron cluster remained almost unaltered, except for a small amount of charge transferred from the inhibitor to the metal cluster. Global and local parameters were successfully compared to calculated ones for other organic inhibitors obtained from natural sources. (C) 2018 Published by Elsevier B.V.
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