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Five novel pyrazolylnucleosides have been evaluated theoretically for their corrosion inhibition efficiency on the Cu(111) surface in acidic media. DFT calculations were carried out to exhibit the intrinsic properties such as lowest unoccupied (ELUMO) and highest occupied (EHOMO) molecular orbital energies, as well as energy gap (∆E), chemical hardness (η), chemical softness (σ), electronegativity (χ), electrophilicity (ω) and nucleophilicity (ε). The theoretical FT-IR spectra were recorded to indicate the presence of the specific bonds in the studied molecules. The surface interactions between the inhibitor molecules and the metal surface were investigated using molecular dynamics simulations and Monte Carlo (MC) simulations. As a result, we have found that the inhibitor pyrazolylnucleosides 5a–e have strong interactions with Cu(111) surface, and therefore have excellent predictive inhibition power against copper corrosion.

Herein, bio-based alginate (Alg) containing-metal atom beads (M= Cu and Ce) were synthesized via an alginate cross-linking method, and studied using experimental techniques combined with theoretical simulations. Firstly, FTIR, TGA and SEM analyses were carried out to study the cross-linking structural features,, thermal stability, and surface morphology. Besides, density functional theory (DFT) methods were used to calculate global reactivity parameters such as HOMO-LUMO energy gaps (ΔEH-L), electronegativity (μ), hardness (η), and electrophilic and nucleophilic indicators using both gas and aqueous media ; the latter for the study of the complexation process. Results showed that Alg@Ce and Alg@Cu beads behave differently and as a function of the increasing temperature. This behaviour c was also predicted by the energy conformer differences between Alg@Ce and Alg@Cu, which were found out theoretically and explained with the combined study of the vibrational modes between the carboxylate group with either Cu or Ce. Overall, the reactivity of the Alg@Ce bead was higher than that of the Alg@Cu counterpart; results could be used as a cornerstone to transfer the materials here studied to a wider range of applications.

The inhibition efficiency of benzoic acid (C1), para-hydroxybenzoic acid (C2), and 3,4-dihydroxybenzoic acid (C3) towards enhancing the corrosion resistance of austenitic AISI 316 stainless steel (SS) has been evaluated in 0.5 M HCl using weight loss (WL), open circuit potential (OCP), potentiodynamic polarization method, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) analysis. The results obtained from the different experimental techniques were consistent and showed that the inhibition efficiency of these inhibitors increased with the increase in concentration in this order C3 > C2 > C1. In addition, the results of the weight loss measurements showed that these inhibitors followed the Villamil isotherm. Quantum chemical calculations and Monte Carlo simulations have also been used for further insight into the adsorption mechanism of the inhibitor molecules on Fe (110). The quantum chemical parameters have been calculated by density functional theory (DFT) at the B3LYP level of theory with 6-31G+(2d,p) and 6-31G++(2d,p) basis sets in gas and aqueous phase. Parameters such as the lowest unoccupied (ELUMO) and highest occupied (EHOMO) molecular orbital energies, energy gap (ΔE), chemical hardness (η), softness (σ), electronegativity (χ), electrophilicity (ω), and nucleophilicity (e) were calculated and showed the anti-corrosive properties of C1, C2 and C3. Moreover, theoretical vibrational spectra were calculated to exhibit the functional hydroxyl groups (OH) in the studied compounds. In agreement with the experimental data, the theoretical results showed that the order of inhibition efficiency was C3 > C2 > C1.

The quantitative structure–property relationship (QSPR) models of the inhibition efficiency of seventeen α-amino acids for copper in acidic medium to their calculated reactivity indicators were developed. DFT calculations and Monte Carlo simulations were employed to find out these indicators. Both multi-linear regression (MLR) and artificial neural network (ANN) methods were employed. The most relevant global descriptors were selected using the simulated annealing algorithm. The QSPR studies showed that the inhibiting performance of the investigated compounds was influenced by their electronegativity, LUMO energy, fraction of electron transferred and total negative charge. The results show that the ANN based model exhibits a great predictive performance compared with MLR model according to correlation coefficient and the root-mean-squared error. In addition, this indicates that the corrosion inhibition of copper by these α-amino acids is mainly a complex phenomenon. Moreover, by analysis of local reactivity indicators and using the ANN constructed model, ten new designed derivative compounds with their predicted inhibition efficiency were proposed. Keywords: Corrosion, Modeling, DFT, Monte Carlo, Simulated annealing, QSPR

The anti-corrosion behavior of biopolymers “sodium alginate (SA) and chitosan compound (CC)” on copper in the 1 M hydrochloric medium was carried out using polarization curves and electrochemical impedance spectroscopy measurements. The obtained results show that the inhibition increases with biopolymers concentration. To better understand the adsorption mechanism, describing the relationship between inhibitory ability and the molecular structure of biopolymers, quantum chemical and Monte Carlo simulation approaches were performed.

Herein, bio-based alginates (Alg) containing metallic beads (Ce and Cu) were synthesized via an alginate cross-linking method, and their properties were studied using experimental techniques combined with theoretical simulations. Materials were characterized through Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) images, to determine the cross-linking structural features, thermal stability, and surface morphology of alginates. Besides, density functional theory (DFT) methods were employed to calculate global reactivity parameters such as HOMO-LUMO gap energies (ΔE

According to the literature, the works on the inhibition of aluminum alloy corrosion using naturally occurring compounds are limited. For this, the inhibiting effect of oil mill liquid by-product (OMW) on the corrosion of 3003 aluminum alloy (AA3003) in molar hydrochloric acid solution was evaluated using electrochemical techniques. In parallel, a computational approach based on DFT/B3LYP and Monte Carlo methods was used to understand the inhibition process under electronic and atomic scales, respectively. The experimental results reveal that OMW has a good inhibiting effect on the corrosion of AA3003 alloy in the tested solution and acts as a cathodic inhibitor. The inhibitory efficiency increases by increasing OMW concentration to attain 89% at 6.0 ppm. The effect of temperature shows that the inhibition efficiency of OMW decreases with temperature rising. Nevertheless, a good prevention capacity of 83% is obtained at 338 K. Such interesting achieved protection property was attributed to the adsorption of OMW constituents onto the alloy surface via a mixed physichemisorption process. This process is found to obey the Langmuir adsorption isotherm. Furthermore, the activation thermodynamic parameters of the corrosion process of AA3003 alloy were also determined and discussed. The computational outcomes outlined the ability of the OMW components to interact favorably with the metal surface, hence the formation of a protective layer, which justified the observed inhibition behaviors. Conferring to the present study, OMW can be used as a good green corrosion inhibitor for AA3003 alloy in the acidic medium.

Biopolymers-based compounds were used by different manners for metal protection toward corrosion phenomena, namely via inhibiting additive and coating strategies. In the last decade, the application of these compounds or their chemically modified forms as effective replacements for toxic inorganic and organic inhibitors attracts more attention. Additionally to their intrinsic chemical stability, biodegradability, eco-friendly, low cost and renewability, biopolymers set were shown the remarkable effect to control the dissolution of several metallic materials in various corrosive environments. Among a large variety of available biopolymers, chitosan and its functionalized form, as well as its nanoparticle composites, have been reported and widely used as good anti-corrosion compounds for different metal/medium systems. In this context, the current chapter aims to shed more light on this subject.

The influence of chitosan on the copper corrosion in sulfide polluted synthetic seawater (SSW) containing 20 ppm of sulfide has been investigated for the first time. Potentiodynamic polarization measurements, electrochemical impedance spectroscopy at the open circuit potential and weight loss measurements were employed to assess the corrosion inhibition ability of chitosan. The impedance studies revealed that in the presence of chitosan at various concentrations, the charge transfer resistance increases. At a concentration of 800 ppm, chitosan exhibited a corrosion inhibition efficiency of 89% following physical adsorption. The influence of temperature and immersion time was studied in sulfide-contaminated synthetic seawater and significant inhibition was observed even after 90 days. SEM-EDS studies confirm the absence of the deterioration products on copper surface.

The inhibitory efficiencies of the molecules tested are determined using weight loss measurements, potentiodynamic polarization and electrochemical impedance (EIS). The adsorption of 1-Methylimidazole and 1H-benzimidazole on metallic surface reinforced with SEM-EDS and UV–Visible analysis of copper surface. These imidazole derivatives are heterocyclic organic compounds containing nitrogen atoms and are of great interest because of their multiple pharmacological activities. A theoretical simulation is achieved for the series of systems studied using density functional theory (DFT) to determine their electronic, structural and energetic properties. Monte Carlo simulation was performed to know well of the relationship between the inhibition ability and molecular structure of imidazole derivatives, the results of the potentiodynamic polarization indicate that the imidazole derivatives are mixed type inhibitors. These reduce the speed of the corrosion process for an optimal concentration of 10-3M. Electrochemical impedance spectroscopy (EIS) shows the presence of a single capacitive loop in favor of the charge transfer mechanism, the corrosion inhibition efficiency of 1-Methylimidazole and and 1H-benzimidazole exceeds approximately 66% 80% respectively. The adsorption of the compounds was found to obey Langmuir adsorption isotherm. A good agreement is observed between the results obtained by the different experimental techniques. Theory-experience correlations are established.

Cysteine's action on 3003 aluminum alloy dissolution in a 2% NaCl solution, at different pH values, has been investigated. Weight-loss measurements, potentiodynamic polarization and electrochemical impedance at OCP were performed. The surface morphology was analyzed by SEM. The main results showed that the alloy underwent severe corrosion at 2 and 11 pH values, as compared to at 5 and 8 pH values. Furthermore, a duality effect of cysteine was noted, as it acted as a corrosion inhibitor or accelerator, depending on its concentration, and on the solution's pH value. This particular behavior can be related to the instability of the formed film adsorbed onto the metal surface. All these findings show the high complexity of cysteine action on 3003 aluminum alloy, under the investigated conditions.

Flocculation is a water and wastewater treatment technology whereby the large aggregation of flocs in water can be formed and be later separated through sedimentation. This review aims to provide the recent developments in the field of natural flocculants and their prospects for the effective removal of dyes or heavy metals from aqueous solutions. It provides a concise information on the types, characteristics and toxicity of dyes or heavy metals. It also covers a comprehensive list of natural flocculants, namely chitosan, starch, microbial, tannin, cellulose, and gelatin (including their derivatives where applicable). In addition, the performances and mechanisms for the removal of dyes or heavy metals as demonstrated by the natural flocculants (and their derivatives) are summarized and thoroughly discussed. Furthermore, the economic analysis of the natural flocculants is elucidated in order to give a perspective on the practicality of this technology in real application. Finally, the future prospects, challenges and recommendations are presented in order to advance the research in natural flocculants. It is anticipated that natural flocculants have a great potential to be further harnessed. By conducting more in-depth scientific research on natural flocculants, more significant breakthroughs can be discovered and this sustainable water treatment will be able to enhance the global water security in the long term.

Some benzoic acid derivatives such as benzoic acid (C1), para-hydroxybenzoicacid (C2), and 3,4-dihydroxybenzoic acid (C3) were investigated as corrosion inhibitors for AISI 316 austenitic stainless steel (SS) in aggressive 0.5 M HCl solution using weight loss (WL) measurements, electrochemical measurements, and scanning electron microscopy (SEM) analysis, radial distribution function (RDF), molecular dynamics (MD). The aim of this work is to determine the inhibition efficiency based on the concentration of studied inhibitors and the temperature effect of medium. The maximum inhibition efficiency (≈ 88%) was obtained in the presence of the optimum inhibitor concentration of 1.0 × 10−2 M for C3 at 291 K. The experimental data showed that the inhibition efficiency of these inhibitors increases with the increase of their concentrations. The temperature effect on the corrosion inhibition of (SS) in 0.5 M HCl with and without inhibitors at different concentrations was investigated from 291 K to 318 K temperature range. It should be noted that each test has been carried out at least three times. Besides, the result was calculated by averaging the obtained values of each test. The activation energy and thermodynamic parameters evaluated from the weight loss measurements, suggested that the adsorption is spontaneous, exothermic, and obeyed the Villamil adsorption isotherm. SEM analyses confirmed that C3 is a good inhibitor compared with C1 and C2. Molecular dynamics simulations diagnosis for molecule/metal interaction showed that the studied organic compounds have strong interactions with Fe (110) and therefore good inhibition power for AISI 316 austenitic stainless steel (SS) against corrosion.

In the current study, the inhibition properties of three cyclic amino acids, namely Histidine (His), Tyrosine (Tyr) and Phenylalanine (Phe), have been investigated using electrochemical techniques for tin corrosion in stagnant 2% NaCl solution at different pH values. To shed more light on the inhibition mechanism, DFT-based computations and Monte Carlo-SAA simulations have been employed. The obtained data revealed that His and Phe compounds have shown the maximum of the inhibition effectiveness at pH 2 and 5, respectively. Besides, without exception, all studied inhibitors have exhibited higher prevention values at pH 5 as compared to pH 2, which was attributed to the ability of those compounds to form hydrogen bonds and interact effectively with the metal surface (SnO2) at pH 5. Furthermore, due to the complexity of the inhibition phenomena, the analysis of calculated intrinsic quantum parameters cannot be used to explain the almost observed inhibition behavior of the studied inhibitors set. On the other hand, agreeing with our results, the conjoint analysis of energetic and geometrical aspects of the adsorption of an inhibitor molecule onto the metal surface is required to get clear insights on the inhibition process.

Three triazoles compounds used as corrosion inhibitors for copper in acidic medium, namely: 1,2,4 triazole (TR), 3-amino 1,2,4 triazole (3 ATR) and 3,5-diamino 1,2,4 triazole (3,5 DATR) have been studied theoretically in aim to investigate the correlation between its molecular reactivity indicators and the corresponding inhibition efficiency. All quantum chemical calculations at the B3LYP/6-31+G(d,p) method were performed with and without solvent effect. In the present paper, not only the neutral inhibitors has been studied, but also the first and the second protonation forms. A good correlation between theoretical and experimental data has been obtained both in gas and aqueous phases, notably for unprotonated inhibitors. Also, the interaction energy between inhibitors and copper has been calculated.

Herein, four tetrazole derivatives namely 1,2,3,4-tetrazole (TZ), 5-amino-1,2,3,4-tetrazole (ATZ), 1-phenyl-1,2,3,4-tetrazole (PTZ) and 1-phenyl-5-mercapto-1,2,3,4-tetrazole (PMTZ) were investigated as corrosion inhibitors on Cu (111) surface in acidic medium. For this purpose, theoretical investigations were carried out preferentially with Density Functional Theory (DFT) at Lee–Yang–Parr correlation functional (B3LYP) using 6-31+g (2d, p) basis set. Numerous global and locale descriptors of reactivity such as EHOMO, ELUMO, energy gap, electronegativity (χ), hardness (η), frontier molecular orbitals repartitions were investigated to describe the reactivity of each molecule. On the other hand, Monte Carlo simulations were investigated on Cu (111) surface to understand the adsorption behavior of the as-studied inhibitors deeply. The adsorption energies (Eads) were also calculated; the results were as follows: PMTZ ˂ PTZ ˂ ATZ ˂ TZ. The experimental inhibition efficiencies were correlated with global descriptors, which confirm that this theoretical study is fruitful for the protection of copper metal in acidic medium.

Herein, the inhibition behavior of alginate biopolymer with different chain length (fragments) on corrosion of Fe (110), Cu (111), Al (111) and Sn (001) surfaces in acidic medium was investigated using quantum chemical calculations and molecular mechanic methods. Based on HSAB's theory, local and global reactivity indicators of different alginate fragments were calculated using DFT/B3LYP/3-21G method. Molecular mechanic simulations were employed to describe quantitatively and qualitatively the adsorption behavior of the bio-inhibitor on the metal surfaces. As a result, the chain length of alginate and metal nature were considerably affected magnitude and trend of alginate/metal interactions. Gradually as the chain length of the alginate molecule was increased, the binding energy increased. On the other hand, it found that the binding of alginate onto metal surfaces followed this order: Sn (001)

Nowadays, theoretical calculation tools have become powerful in predicting the behavior of corrosion inhibitors on the surface of metals and, therefore, avoiding energy consumption and the cost of experimental tests. This work aims to predict the inhibitory power of some furan derivatives on Cu (111), Fe (110), Al (111) and Sn (111) surfaces in acidic media. For this purpose, three furan derivatives&mdash, furan-2-carbaldehyde (FF1), 5-(hydroxymethyl)furfural (FF2) and 5-(hydroxymethyl)furoic acid (FF3)&mdash, have been selected to compare their intrinsic properties against corrosion as well as their behavior on iron (Fe), copper (Cu), aluminum (Al) and tin (Sn) surfaces in acid medium. Typically, the anti-corrosive properties of FF1, FF2 and FF3 were studied by using quantum chemical calculations and Monte Carlo simulations. Density Functional Theory (DFT), lowest unoccupied (ELUMO) and highest occupied (EHOMO) molecular orbital energies, energy gap (∆E), chemical hardness (&eta, ), softness (&sigma, ), electronegativity (&chi, ), electrophilicity (&omega, ) and nucleophilicity (&epsilon, ) have been calculated and discussed. Theoretical vibrational spectra were also calculated to exhibit the functional groups in the selected chemicals. On the other hand, the adsorption behaviors of FF1, FF2 and FF3 were studied on the Fe(110), Cu(111), Al(111) and Sn(111) surfaces. As a result, the adsorption energies of all molecules are ordered as Fe(110) &lt, Cu(111) &lt, Al(111) &lt, Sn(111) and FF3 seems to be more effective as a corrosion inhibitor due to the existence of both carboxylic acid and hydroxyl groups, which consist of favorable sites of adsorption into the metal surface.

In this study, the electrochemical corrosion behavior of copper was investigated in seawater collected from four different marine zones of Agadir coastal. These zones are different by the degree of pollution in order to study the effect of this pollution on the copper corrosion, especially the microbial pollution by sulfate reducing-bacteria (SRB). So, to prove this relationship, the microbiological analyses researching the SRB are realized. In parallel, the electrochemical impedance measurement and atomic absorption analysis are established to compare the microbiological evolution cycles with the electrochemical behavior of copper during the immersion period. In the results, we found a good correlation between the growth cycle of marine sulfate-reducing bacteria and the copper corrosion rate by the sulfur and extracellular polymeric substances (EPS) produced as bacteria metabolites. Additionally, this corrosion rate depends on the immersed time: it is maximal after the first or second month depending on the marine zone.

This work ultimately pays careful consideration to a method that respects the environment, and that can be developed across the accumulation of research to reduce the corrosion of metals in sea water. Extracts of Ziziphus lotus (wild jujube) were tested as a corrosion inhibitor of copper in sea water, using polarization methods and weight loss measurements. We also present by SEM the morphology of copper surface analyzed after immersion in inhibited and uninhibited electrolytes. The inhibition efficiency of Ziziphus lotus extracts was calculated and compared. We note good agreement between these methods. The obtained results revealed that the tested inhibitor significantly reduced the kinetics of the corrosion process of copper. Its efficiency increases with the concentration, and attained 93% at 5 g/L. The effect of temperature on the corrosion behavior of copper in natural sea water was also studied in the range of 293 K and 323 K, to determine thermodynamic data of activation.

Biopolymers-based compounds were used by different manners for metal protection toward corrosion phenomena, namely via inhibiting additive and coating strategies. In the last decade, the application of these compounds or their chemically modified forms as effective replacements for toxic inorganic and organic inhibitors attracts more attention. Additionally to their intrinsic chemical stability, biodegradability, eco-friendly, low cost and renewability, biopolymers set were shown the remarkable effect to control the dissolution of several metallic materials in various corrosive environments. Among a large variety of available biopolymers, chitosan and its functionalized form, as well as its nanoparticle composites, have been reported and widely used as good anti-corrosion compounds for different metal/medium systems. In this context, the current chapter aims to shed more light on this subject.