Research Article Anticorrosive Effect of Halogenated Aniline Enaminoesters on Carbon Steel in HCl Mariana F. P. Carlos , Geicy K. P. Barboza , and Aurea Echevarria Department of Organic Chemistry, Institute of Chemistry, Federal Rural University of Rio de Janeiro, Seropedica 23.890-000, Brazil Correspondence should be addressed to Aurea Echevarria; echevarr@ufrrj.br Received 22 February 2022; Revised 15 April 2022; Accepted 20 April 2022; Published 27 May 2022 Academic Editor: Michael J. Schütze Copyright © 2022 Mariana F. P. Carlos et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Four enaminoesters derived from halogenated aniline, with potential anticorrosion activity, were synthesized and tested against carbon steel AISI 1020 in acid medium using 1.0 mol L -1 HCl. The synthesis was demonstrated through the reaction of ethyl acetoacetate with four different amines, in the presence of glacial acetic acid and molecular sieve, using ethanol as solvent for 24 h. The evaluation of the anticorrosive activity was performed using the gravimetric technique and electrochemical methods, such as electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PP). Results indicated that the F-EN (Ethyl (2Z)-3-[(4-fluoro-phenyl)-amino]-but-2-enoate) inhibitor had higher corrosion inhibition efficiency, of 98% by mass loss, and 85% by electrochemical techniques. Adsorption obeyed the Langmuir isotherm, thus suggesting that the inhibitors form a monolayer film in metal surface. These results also contributed to the calculations of the physicochemical parameters of E a , △H ≠ ads , and △S ≠ ads , which confirmed the corrosion inhibition when compared to the absence of the inhibitors. 1. Introduction Corrosion is the process of spontaneous deterioration of a material that affects several industrial segments globally, causing major economic problems such as replacement of equipment, and thus needs investigation for its control [1–3]. Due to the mechanical properties of carbon steel, of its low cost, and being easily handled, it is generally used in different industries, such as production, chemical process- ing, petroleum transportation, and refining, thus being exposed to salts, gases, and acids, and consequently, condi- tioned to many corrosive processes [4, 5]. Its susceptibility to corrosion reinforces the importance of developing new efficient methods of combating it; however, their efficiency is conditioned to the comprehension and characterization of the various corrosive media accountable for the deteriora- tion of the material [6, 7]. Although there are several methods to protect against the corrosive environment, the use of corrosion inhibitors has been widely used due to low cost, simple process, strong adaptability, and economic efficiency [1]. Inhibitors are organic or inorganic substances that can reduce or eliminate corrosion, slowing down the anodic and/or cathodic reactions on the metal surface [6, 8]. The use of organic molecules as inhibitors is already widely studied as a promising alternative since they associate with the metal by adsorption, thus protect- ing the surface [9, 10]. Physical adsorption involves electro- static interaction between inhibitory agents and the metal surface, whereas chemical adsorption involves charge splitting or electron transfer from the organic molecule to the metal surface [11]. The adsorption properties are related to the pres- ence of unsaturation (π electrons) and the presence of hetero- atoms, such as nitrogen and oxygen, where the transfer of their nonbonding electron pairs to the d orbitals of the Fe atoms on the metal surface, by a coordinated bond, causing the surface of the metal to be covered [12–15]. Enaminoesters are common representatives of the enami- nones class, which refers to compounds that have the conju- gated bonds (N-C=C-C=O), combining the nucleophilicity of enamines with the electrophilicity of enones, thus being considered very versatile intermediates [16]. These com- pounds have structures with electronic acceptor-donor Hindawi International Journal of Corrosion Volume 2022, Article ID 7218063, 15 pages https://doi.org/10.1155/2022/7218063