An Intelligent and Efficient Synthesis of New Inhibitors against Corrosion of Mild Steel in Acidic Media

• Published in: Surface engineering and applied electrochemistry Vol. 57; no. 1; pp. 136 - 147
• Main Authors: Nadia Arrousse, Nahlé, Ayssar, Mabrouk, El Houssine, Salim, Rajae, El hajjaji, Fadoua, Rais, Zakia, Taleb, Mustapha
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2021; Springer Nature B.V
• Subjects: Absorption spectra; Benzoates; Benzoic acid; Corrosion; Corrosion effects; Corrosion inhibitors; Density functional theory; Engineering; Esters; Ethanol; Fluorescein; Low carbon steels; Machines; Manufacturing; NMR; Nuclear magnetic resonance; Pigments; Processes; Sodium hydroxide; Surface analysis (chemical); Synthesis; synthesis; fluorescein; scanning electron microscopy; theoretical study; esterification; hybrid density-functional theory method; corrosion inhibitor; energy dispersive X-ray analysis
• ISSN: 1068-3755; 1934-8002
• DOI: 10.3103/S1068375521010026

In this present work, the theoretical study of the synthesis of methyl 2-(6-hydroxy-3-oxo-3
H
-xanthen-9-yl) benzoate and ethyl 2-(6-hydroxy-3-oxo-3
H
-xanthen-9-yl) benzoate, using the Gaussian 09 based on the hybrid density functional theory method (DFT/B3LYP/6-311G (
d
,
p
)) was done. From the obtained results, an economical method for the synthesis of these compounds with a high yield was elaborated. This method involved two steps: the first one was the preparation of the 2-(6-hydroxy-3-oxo-3
H
-xanthen-9-yl) benzoic acid by a reaction of an open-form fluorescein in a 1.0 M sodium hydroxide solution; and the second one was the formation of the corresponding esters using anhydrous methanol and ethanol. Those esters were characterized by conventional spectroscopic techniques, such as nuclear magnetic resonance, infrared, and mass spectroscopies. The theoretical results are in good correlation with those obtained experimentally. The analysis of the absorption spectra revealed that the synthesized compounds are colored pigments. The experimental study of the inhibition effect of those compounds on the corrosion of mild steel in a 1 M HCl solution performed using absorbance difference measurements demonstrated that the synthesized products are good inhibitors in an acidic environment at a concentration of 1.0 × 10
–4
M. The surface analysis via the scanning electron microscope/dispersive X-ray technique showed that those compounds protect mild steel against corrosion by being adsorbed on its surface.