New triazepine carboxylate derivatives: correlation between corrosion inhibition property and chemical structure

International Journal of Industrial Chemistry https://doi.org/10.1007/s40090-019-00199-5 RESEARCH New triazepine carboxylate derivatives: correlation between corrosion inhibition property and chemical structure K. Alaoui1 · Y. El Kacimi1 · M. Galai1 · H. Serrar2 · R. Touir1,3 · S. Kaya4 · C. Kaya4 · M. Ebn Touhami1 Received: 9 April 2019 / Accepted: 18 December 2019 © The Author(s) 2020 Abstract In this investigation, attempts have been made to study the corrosion inhibition properties of three new triazepine carboxylate compounds for mild steel in 1.0 M hydrochloric acid medium. The evaluation was carried out using mass loss, electrochemical impedance spectroscopy and polarization curves measurement. Impedance diagrams and Bode plots for uninhibited and inhibited systems were analyzed using Zview program. The fitted data observed trails in nearly the same pattern as the experimental results. It is showed that triazepine carboxylate compounds are very good inhibitors for mild steel corrosion in 1.0 M hydrochloric acid medium which act as mixed-type inhibitors. So, the inhibition efficiency was increased with inhibitor concentration in the order Cl–Me–CN > Me–CN > Cl–Me–CO2Et which depended on their molecular structures. Electrochemical impedance spectroscopy showed that all compounds act by the formation of a protective film at the metal surface. Surface analyses via SEM and Optical 3D profilometry were used to investigate the morphology of the steels before and after immersion in 1.0 M HCl solution containing inhibitors. The correspondence between inhibition property and molecular structure of the triazepine carboxylate compounds was investigated, using density functional theory (DFT). Experimental and DFT study was further supported by molecular dynamic simulations study. Keywords Organic compounds · Triazepine carboxylate derivatives · Molecular dynamics · Ab initio calculations · Computer modeling and simulation · Corrosion inhibition · SEM · Optical 3D profilometry Introduction Hydrochloric acid pickling bath is used to remove the corrosion products from the metal working. Over-pickling can cause serious damage and physical properties of metals’ structure can be easily done [1]. Thus, to control the risk and reduce the problem, several organic compounds are used as corrosion inhibitors [2–5]. * K. Alaoui * Y. El Kacimi 1 Laboratory of Materials Engineering and Environment: Application and Modeling, Faculty of Science, Ibn Tofail University, PO Box 133, 14000 Kenitra, Morocco 2 Laboratory of Organic, Organometallic Chemistry, Faculty of Science, Ibn Tofaïl University, Kenitra, Morocco 3 Centre Régional des métiers de l’éducation et de la formation, Madinat Al Irfane, BP 6210 Rabat, Morocco 4 Faculty of Science, Department of Chemistry, Cumhuriyet University, 58140 Sivas, Turkey Currently, most of the effective inhibitors used have in their structure: 1. heteroatoms such as oxygen (O), nitrogen (N), phosphorus (P), sulfur (S); 2. aromatic component having multiple bonds leading to easier adsorption on the metal surface; 3. functional groups such as = NH, –CHO, –C≡N, –N = N–…; 4. heterocyclic compounds such as imidazole, quinoline, quinoxaline, phenyltetrazole, etc. [6, 7]. In this case, we have established that triazepine carboxylate compounds can easily be protonated in acidic medium, thus getting adsorbed on the surface metal. Recently, some workers have reviewed and provided a literature survey of triazepines compounds. The synthesis and characterization of a family of triazepine derivatives are of particular interest to the chemical and biological communities, and hence the chemistry and biochemistry of triazepine derivatives have been intensively investigated. Triazepine 13 Vol.:(0123456789) International Journal of Industrial Chemistry derivatives have diverse applications in wide-ranging fields, they have remarkable biological importance and medicinal and pharmaceutic potential. Some known derivatives of imidazotriazepines have shown activity as muscle relaxants, while others have antifungal, antidiabetic, antimicrobial, antiviral, anticancer, and analgesic properties [8–10]. Propelled by our interest in the synthesis of new efficient inhibitors, triazepines carboxylate substituted compounds (Cl–Me–CO2Et, Cl–Me–CN and Me–CN) have been developed, representing a promising way to improve the performance of corrosion inhibition in aggressive hydrochloric acid solution, owing to the existence of the cyano group. The objective of the present paper is to study the inhibition efficiencies of triazepine carboxylate derivatives on mild steel corrosion in 1.0 M HCl and compare using weight loss measurements, electrochemical impedance spectroscopy, and potentiodynamic polarization analysis. Furthermore, quantum chemical calculations of density function theory (DFT) and molecular dynamics (MD) simulations were applied to theoretically determine the relationship between molecular structure and inhibition efficiency. Surface morphology of the mild steel before and after exposing to 1.0 M HCl medium is also examined and discussed using scanning electron microscopy (SEM) and using 3D-profilometry images. Experimental details Materials and weight loss measurements Mild steel specimens used have a rectangular form of 2.5 cm × 2.0 cm × 0.05 cm and have the following chemical composition (wt%): C, 0.11; Si, 0.24; Mn, 0.47; Cr, 0.12; Mo, 0.02; Ni, 0.1; Al, 0.03; Cu, 0.14; Co, < 0.012; V, < 0.003; W, 0.06; Fe, balance. The samples’ surface was polished with emery paper, rinsed with distilled water, degreased with ethanol, and dried in hot air. The immersion time for mass loss was 6 h at 298 ± 2 K. After immersion period, the samples were cleaned according to ASTM practice standard, and reweighed to 10−4 g for determining corrosion rate [11, 12]. The hydrochloric acid pickling medium (1.0 M HCl) was prepared by dilution of analytical grade 37% of HCl with distilled water. Electrochemical cell The electrolysis cell used for potentiodynamic polarization measurement was a borosilicate glass cylinder closed by a cap with five apertures. The mild steel used as working electrode was pressure-fitted into a Polytetrafluoroethylene holder exposing only 1 cm2 of area to the 1.0 M hydrochloric acid medium. Platinum and saturated calomel were 13 used as counter and reference electrode, respectively. All potentials were measured against the previous electrode. The potentiodynamic polarization curves were recorded by changing the electrode potential automatically from negative values to positive values versus E OCP using a potentiostat/galvanostat type PGZ 100, at a scan rate of 1 mV/s after 30 min of immersion time until reaching steady state. The test solution was thermostatically controlled at 298 ± 2 K in air atmosphere without bubbling. To evaluate corrosion kinetic parameters, a fitting by Stern–Geary equation was used. 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