Phenylcoumarin Glucoside as a Natural Inhibitor in the Protection of Low Carbon Steel Against Corrosion
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Phenylcoumarin Glucoside as a Natural Inhibitor in the Protection of Low Carbon Steel Against Corrosion Héctor M. Barbosa Cásarez1, Araceli Espinoza Vázquez *1, Francisco J. Rodríguez-Gomez1 1
Facultad de Química, Edificio D, Circuito de la Investigación Científica S/N CP 04510 Ciudad de México
Corresponding author: [email protected]
Abstract
Phenylcoumarin glucoside (4-PC) is a compound extracted from the plant Hintona latiflora and was studied as inhibitor for AISI 1018 steel corrosion in 3% NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques, which may find application as eco-friendly corrosion inhibitors. The 4-PC provides inhibitor properties that protect AISI 1018 low carbon steel against corrosion at low concentrations (5 ppm) obtained by EIS. Polarization studies showed that the inhibitor was of mixed type. The inhibition efficiency by the two electrochemical techniques shows similar results. The inhibitor adsorption was demonstrated to be a combined process (physisorption and chemisorption) according to the Langmuir isotherm.
Introduction Corrosion has been identified as the primary mechanism causing pipeline failures, which result in economic loss and environmental problems. In literature, it has been mentioned that the inhibitors are substances capable of stopping the spread of the corrosion in materials for a certain period, and using small quantities (ppm) [1]. Recently, a great number of natural inhibitors have been discovered all over the world by extracting compounds from plants, like Ptychotis verticillate [2], Morus alba pendula [3], and Artemisia mesatlantica [4], all of which show an efficiency between 60% and 70% as inhibitors. Unfortunately, their disadvantage is that they are constituted by a mixture of organic compounds. Some of the characteristics that natural inhibitors must have are the following: they must contain oxygen, nitrogen and other heteroatoms, with free-pair electrons in their chemical structure. In this work, phenylcoumarin glucoside, (5-O-β-Dglucopyranosyl-7-methoxy-3',4'-dihydroxy-4-phenylcoumarin) known as 4-PC was isolated (Figure 1). The objective of this work is to evaluate the efficiency of phenylcoumarin glucoside as a corrosion inhibitor, as well as its mechanisms. Downloaded from https://www.cambridge.org/core. North Carolina State University, on 30 Dec 2017 at 05:35:38, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2017.618
H3CO
O
O
O
O
HO
HO
OH OH
OH OH
Figure 1. Chemical structure of 4-PC
Experimental details Phenylcoumarin glucoside dissolution preparation A solution of 0.01 M of phenylcumarine glucoside (4-PC), 95% pure, dissolved in ethanol, was prepared. Afterwards, inhibitor concentrations of 5, 10, 20 and 50 ppm were used in the corrosive solution of 3 % p/v NaCl. Electrochemical evaluation
Electrochemical evaluation was carried out at 20°C, and corrosion potential was monitored for approximately 1800 seco
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