Synthesis, experimental, quantum chemical and molecular dynamics study of carbon steel corrosion inhibition effect of two Schiff bases in HCl solution

Chitosan/tannic acid phenamine networks-hollow mesoporous silica capsules with reversible pH response: Controlled-releasing amino acid derivatives as "green" corrosion inhibitor

A novel amino acid derivative (SM) was synthesized through Schiff base reaction between syringaldehyde (SA) and methionine (MTI), and loaded to obtain a reversible pH-responsive releasing corrosion inhibitor silica capsule (CS/TA@SM@HMSs) with chitosan/tannic acid phenamine networks on the surface. The corrosion inhibition effect of SM and CS/TA@SM@HMSs on Q235 was studied using electrochemical techniques and surface analysis. The results showed the maximum inhibition efficiency of SM reached to 93.2 % at 200ppm by immersing Q235 in 3.5 wt% NaCl solution. The theoretically calculated electron parameter (the energy gap ΔE = 4.492 eV) indicated that SM molecules were more susceptible to electron transfer with iron surfaces therefore allowing better adsorption on carbon steel surfaces to prevent corrosion. Meanwhile, UV-visible measurements showed that the chitosan/tannic acid phenamine network on the capsule surface responded to changes in pH. The reversible pH-responsive corrosion inhibitor capsule can be switched on and off several times to release SM, demonstrating reversible release and efficient corrosion protection. This study proposes a novel class of "green" amino acid derivative corrosion inhibitors, and establishes a controllable, efficient and reversible pH-responsive release system. A new approach is provided to stimulating the release of corrosion inhibitors in response to long-term corrosion protection of metals.

Synthesis, experimental and computational studies on the anti-corrosion performance of substituted Schiff bases of 2-methoxybenzaldehyde for mild steel in HCl medium

Corrosion inhibition performance of two synthesized Schiff base ligands; (E)-2-((2-methoxybenzylidene)amino)phenol L1 and (E)-2-((4-methoxybenzylidene)amino)phenol L2 were carried out by weight loss measurement in 0.1 M hydrochloric acid (HCl) solution. Density Functional Theory (DFT) and Molecular dynamics (MD) simulation were applied to theoretically explain the inhibitors' intrinsic properties and adsorption mechanism in the corrosion study. The result of the inhibition performances carried out at varying concentrations and temperatures were compared. The corrosion inhibition efficiencies of L1 and L2 at an optimal concentration of 10 × 10^-4 M were 75% and 76%. Langmuir isotherm model fits the data obtained from the experiment with a correlation coefficient (R²) value closer to unity. The adsorption mechanism of inhibitor on the surface of the Fe metal occurred via chemisorption inferred from the Gibbs free energy (ΔG_ads). Scanning electron microscopy showed a mild degradation on the surface of the mild steel immersed in the L1, and L2 inhibited acid solution, which could be due to surface coverage. The energy dispersive X-ray spectroscopy showed the metal surface's elemental composition and the existence of the chlorine peak, which emanates from the HCl medium. DFT calculations revealed that the hybrid B3LYP functional performed better than the M06-2X meta-functional in estimating the energies of the synthesized Schiff bases for corrosion inhibition as seen in the lower ΔE values of 3.86 eV and 3.81 eV for L1 and L2. The MD simulation revealed that the orientation of inhibitors on the surface of the metal resulted in the coordination bond formation and that the interaction energy of L2 was -746.84 kJ/mol compared to -743.74 kJ/mol of L1. The DFT and MD results agreed with the observed trend of the experimental findings.

Organic Compounds as Corrosion Inhibitors for Carbon Steel in HCl Solution: A Comprehensive Review

Most studies on the corrosion inhibition performance of organic molecules and (nano)materials were conducted within "carbon steel/1.0 M HCl" solution system using similar experimental and theoretical methods. As such, the numerous research findings in this system are sufficient to conduct comparative studies to select the best-suited inhibitor type that generally refers to a type of inhibitor with low concentration/high inhibition efficiency, nontoxic properties, and a simple and cost-economic synthesis process. Before data collection, to help readers have a clear understanding of some crucial elements for the evaluation of corrosion inhibition performance, we introduced the mainstay of corrosion inhibitors studies involved, including the corrosion and inhibition mechanism of carbon steel/HCl solution systems, evaluation methods of corrosion inhibition efficiency, adsorption isotherm models, adsorption thermodynamic parameters QC calculations, MD/MC simulations, and the main characterization techniques used. In the classification and statistical analysis section, organic compounds or (nano)materials as corrosion inhibitors were classified into six types according to their molecular structural characteristics, molecular size, and compound source, including drug molecules, ionic liquids, surfactants, plant extracts, polymers, and polymeric nanoparticles. We outlined the important conclusions obtained from recent literature and listed the evaluation methods, characterization techniques, and contrastable experimental data of these types of inhibitors when used for carbon steel corrosion in 1.0 M HCl solution. Finally, statistical analysis was only performed based on these data from carbon steel/1.0 M HCl solution system, from which some conclusions can contribute to reducing the workload of the acquisition of useful information and provide some reference directions for the development of new corrosion inhibitors.

Corrosion inhibition studies of ferrocenyl Schiff bases in a mild acidic medium through experimental methods and DFT calculations

The organometallic ferrocenyl Schiff bases were synthesized and tested as anticorrosive material on AA2219-T6 in acidic medium using Tafel polarization, EIS, weight loss analysis, FT-IR spectroscopy and theoretically proved by DFT.

Ab initio molecular dynamics simulations on the adsorption of 1-hydroxyethane-1,1-diphosphonic acid on the iron (100) surface

Through IRI, Bader charges and ELF analysis, an electrostatic interaction network exists between HEDP and the iron (100) surface, which is responsible for the stability of the adsorption state.

A new fluorescence probe for detection of Cu+2 in blood samples: Circuit logic gate

A Fluorescence probe was designed based on 8-hydroxyquinoline chitosan silica precursor (HQCS) for selective detection of Al³⁺, Cu²⁺. The HQCS has no observable fluorescence signal, but after the addition of Al³⁺, a huge fluorescence signal appeared, and the selective quenching was absorbed after the addition of Cu²⁺. The effect of other different cations, including Cu²⁺, Mg²⁺, Ca²⁺, Pb²⁺, Zn²⁺, Hg²⁺, Ag⁺, Fe^3+, and K⁺ was studied. The addition of Cu²⁺ to the probe (HQCSAL) decreased the fluorescence very repeatable, and the variation of the fluorescence vs. Cu²⁺ was monotonic and linear. Therefore, the prepared probe was used to determine Cu²⁺ ions in real samples. The mechanism of fluorescence variation by adding cations to the probe solution was studied using the Stern-Volmer equation. Under the optimum conditions, the linear range and detection limit were 3.5-31 μM and 1 μM, respectively. The probe accuracy on the copper determination in the blood and tap waters was comparable to the ICP-OES results. The circuit logic gate mimic was designed for the fluorescence behavior of the probe constituents.

Plant Extracts as Green Corrosion Inhibitors for Different Metal Surfaces and Corrosive Media: A Review

Natural extracts have been widely used to protect metal materials from corrosion. The efficiency of these extracts as corrosion inhibitors is commonly evaluated through electrochemical tests, which include techniques such as potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss measurement. The inhibition efficiency of different extract concentrations is a valuable indicator to obtain a clear outlook to choose an extract for a particular purpose. A complementary vision of the effectiveness of green extracts to inhibit the corrosion of metals is obtained by means of surface characterizations; atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy analysis are experimental techniques widely used for this purpose. Moreover, theoretical studies are usually addressed to elucidate the nature of the corrosion inhibitor—metal surface interactions. In addition, calculations have been employed to predict how other organic substances behave on metal surfaces and to provide experimental work with fresh proposals. This work reports a broad overview of the current state of the art research on the study of new extracts as corrosion inhibitors on metal surfaces in corrosive media. Most constituents obtained from plant extracts are adsorbed on the metal, following the Langmuir adsorption model. Electron-rich regions and heteroatoms have been found to be responsible for chemisorption on the metal surface, whereas physisorption is due to the polar regions of the inhibitor molecules. The plant extracts compiled in this work obtained corrosion inhibition efficiencies above 60%, most of them around 80–90%. The effect of concentration, extraction solvent, temperature, and immersion time were studied as well. Additional studies regarding plant extracts as corrosion inhibitors on metals are needed to produce solutions for industrial purposes.

Galactomannan as a new bio-sourced corrosion inhibitor for iron in acidic media

The aim of this study is to evaluate the impact of a bio-sourced polymer as a corrosion inhibitor against iron corrosion in a 1 M HCl solution. Galactomannan was obtained from the carob plant (Ceratonia Siliqua L) and its structure was verified by infrared spectroscopy (FTIR) and elemental analysis. The inhibitor concentration effects and immersion time on the resistance of the iron surface against corrosion are evaluated using impedance and polarization electrochemical measurements, UV-visible analysis and theoretical study. The results show that the galactomannan is a mixed type inhibitor act by physisorption and chemisorption on the metal surface. In addition, the efficiency of these compounds increases with increasing the concentration of the inhibitor and reaches a value of 87.72% at a concentration of 1 g/l. The electrode surface was characterized by SEM surface analysis method coupled with EDS.

Synthesis of Macromolecular Aromatic Epoxy Resins as Anticorrosive Materials: Computational Modeling Reinforced Experimental Studies

Herein, two bifunctional macromolecular aromatic epoxy resins (ERs), namely, 4,4'-isopropylidenediphenol oxirane (ERH) and 4,4'-isopropylidene tetrabromodiphenol oxirane (ERBr), are synthesized, characterized, and evaluated as anticorrosive materials for carbon steel corrosion in acidic medium. ERs were characterized using proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy techniques. Investigated ERs acted as effective corrosion inhibitors, and their inhibition effectiveness followed the order ERBr (96.5%) > ERH (95.6%). Potentiodynamic polarization results showed that ERH and ERBr behave as predominantly anodic type and the cathodic type of corrosion inhibitors, respectively. Adsorption of both the studied ERH and ERBr molecules obeyed the Langmuir adsorption isotherm model. Density functional theory and molecular dynamics studies showed that protonated forms of ERH and ERBr contribute more to metal (carbon steel)-inhibitor (ERH/ERBr) interactions than their neutral forms.

Synthesis, characterization and corrosion inhibition behavior of 2-aminofluorene bis-Schiff bases in circulating cooling water

Two new bis-Schiff bases, namely 2-bromoisophthalaldehyde-2-aminofluorene (M1) and glutaraldehyde 2-aminofluorene (M2) were synthesized and were characterized, the potentiodynamic polarization curve confirmed that they were anode type inhibitors.