Synthesis, characterization, and evaluation of xanthene derivative as highly effective, nontoxic corrosion inhibitor for mild steel immersed in 1 M HCl solution

Synthesis, Characterization, Antibacterial, Antifungal and Anticorrosion Activities of 1,2,4-Triazolo[1,5-a]quinazolinone

The synthesis of 5,6,7,8-tetrahydro-[1,2,4]triazolo[5,1-b]quinazolin-9(4H)-one (THTQ), a potentially biologically active compound, was pursued, and its structure was determined through a sequence of spectral analysis, including ¹H-NMR, ¹³C-NMR, IR, and HRMS. Four bacterial and four fungal strains were evaluated for their susceptibility to the antibacterial and antifungal properties of the THTQ compound using the well diffusion method. The impact of THTQ on the corrosion of mild steel in a 1 M HCl solution was evaluated using various methods such as weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) analysis. The study revealed that the effectiveness of THTQ as an inhibitor increased with the concentration but decreased with temperature. The PDP analysis suggested that THTQ acted as a mixed-type inhibitor, whereas the EIS data showed that it created a protective layer on the steel surface. This protective layer occurs due to the adsorption behavior of THTQ following Langmuir's adsorption isotherm. The inhibition potential of THTQ is also predicted theoretically using DFT at B3LYP and Monte Carlo simulation.

Inhibitory Capabilities of Sweet Yellow Capsicum Extract toward the Rusting of Steel Rebars in Cement Pore Solution

The inhibitory capabilities of the sweet yellow capsicum extract (SYCE) toward the rusting of steel rebars in cement pore solution (CPS) were tested employing the electrochemical and mass loss methods. Gallic acid, caffeic acid, p-coumaric acid, ferulic acid, luteolin, and cinnamic acid are the most important constituents in the SYCE extract. By adsorbing them on steel bars, the organic compounds in the CSA extract enable them with an effective mixed-type inhibition, suppressing both anodic and cathodic procedures. At 300 ppm, the highest performances were 95.3 and 97.5% utilizing mass loss and electrochemical approaches, respectively. The activation energy for the corrosion process is greatly increased by the addition of the SYCE extract, going from 13.2 kJ mol^-1 (blank solution) to 30.0 kJ mol^-1 (300 ppm SYCE extract). The physical adsorption actions of the SYCE extract are described by the Freundlich equilibrium constant's smallest value, which is 0.074 ppm^-1. Many future investigators will be attracted by these discoveries to work relentlessly to uncover the anti-corrosion characteristics of novel plant extracts in the area of concrete additives.

Colloidal and interface aqueous chemistry of dyes: Past, present and future scenarios in corrosion mitigation

The most effective corrosion inhibitors are organic compounds, especially heterocyclic ones with a certain balance of hydrophilicity, hydrophobicity, and conjugation. Most dyes develop the critical characteristics of a substance that can be utilized as an effective corrosion inhibitor. These include the presence of polar functional groups, nonbonding electrons and multiple bonds of the aromatic ring(s) and side chains. In aqueous electrolytes, dyes efficiently bind to metal surfaces through their electron-rich spots, known as adsorption centers. Literature studies show that many dye series have excellent anticorrosive properties for many metal/electrolyte combinations. They contain many electron-donating sites and behave as polydentate and chelating ligands. The polar functional for instance -OH, -CONH₂, -NH₂, -OR, -SO₃H, -COOH, -NMe₂, -N=N-, -CHO, -N=C < etc. also help in solubilizing relatively complex dye molecules in aqueous electrolytes. This review work seeks to explain the interfacial adsorption of dye molecules and how that negatively affects metallic corrosion. Through their adsorption, dye molecules block the active sites. They mainly achieved this by employing the Langmuir isotherm model. Additionally, the mechanism of corrosion inhibition is investigated, with a special emphasis on dyes.

Theoretical Study and Adsorption Behavior of Urea on Mild Steel in Automotive Gas Oil (AGO) Medium

The continuous search for eco-friendly corrosion inhibitors due to differences in corrosive media remains an important point in corrosion control. The experimental studies on the corrosion inhibition of urea on mild steel in automotive gas oil (AGO) was conducted using gasometric techniques and scanning electron microscope (SEM). The theoretical approach on the density functional theory (DFT) on the urea molecule was carried out using Gaussian 09 software. The adsorption behavior of urea molecules on the surface of the mild steel was analyzed using Frumkin and Flory-Huggins adsorption isotherms models and Gibb’s free energy, respectively. The result of the experimental study shows a poor corrosion inhibitory effect of urea on mild steel in automobile gas oil (AGO) medium as the inhibition efficiency decreased from 69.30% in week 1 to 12% in week 11 at 200 ppm of inhibitor. The adsorption of urea on the mild steel surface obeys Frumkin’s adsorption isotherm model. Gibb’s free energy of adsorption of urea molecules onto mild steel surface revealed a physisorption mechanism. SEM results showed the non-inhibitive nature of urea on the studied mild steel. Quantum chemical parameters such as HOMO, LUMO, electron affinity, electronegativity, and the fraction of electrons transferred to the metal surface were calculated and interpreted to compare the experimental and theoretical results. The theoretical findings in the current investigation were not in agreement with the experimental result, thereby creating a need for further study using the electrochemical method.

Thiophene derivatives as corrosion inhibitors for 2024-T3 aluminum alloy in hydrochloric acid medium

Thiophene derivatives, namely (E)-thiophene-2-carbaldehyde oxime (OXM) and (E)-5-(thiophen-2-yl)-1H-tetrazole (TET), were synthesized and characterized via¹H and ¹³C NMR. Furthermore, their inhibitory property for AA2024-T3 in 1 M HCl solution was investigated via electrochemical impedance spectroscopy and potentiodynamic polarization at 293 K, together with DFT/B3LYP-based calculations. Numerous global and local descriptors of reactivity such as EHOMO, ELUMO, energy gap, electronegativity (χ), hardness (η), and frontier molecular orbital repartitions were investigated to describe the reactivity of each molecule. Alternatively, Monte Carlo simulations were performed under the solvation condition on the Al (111) surface to understand the adsorption behavior of the as-studied inhibitors deeply. The inhibition efficiency increased with an increase in the inhibitor concentration, achieving maximum values of 94.0% and 96% at 10⁻³ M, respectively. The polarization curves showed that the examined compounds act as mixed-type inhibitors. In addition, the adsorption of these compounds obeyed the Al Awady, Flory-Huggins and Temkin isotherms. The surface characterization analysis via SEM/EDX confirmed the presence of a barrier layer covering the aluminum surface. The experimental inhibition efficiencies were correlated with global descriptors, which confirmed that this theoretical study is useful for the protection of aluminum alloy metal in an acidic medium.

Thiophene derivatives: thiophene-2-carbaldehyde oxime (OXM) and 5-(thiophen-2-yl)-1H-tetrazole (TET), were synthesized and characterized. Furthermore, their inhibitory property for AA2024-T3 in 1 M HCl solution was investigated via electrochemical and with theoretical study.