M. SAID Mohamed elhadi

The inhibition of API 5L Grade B steel corrosion in sulfuric acid solution in the presence of some pyridinium salt derivatives such as 1,1′-methylenebis(pyridin-1-ium)bromide (pyridinium salt 1) and 1,1′-(ethane-1,2-dyl))bis(pyridin-1-ium)bromide (pyridinium salt 2) was conducted using weight loss techniques, potentiodynamic polarization methods, electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and theoretical calculations. Various parameters were determined and discussed to fully understand the mode of action of these compounds, including thermodynamic activation, adsorption, and quantum chemical parameters. The results obtained by all techniques revealed that these derivatives are suitable inhibitors for this type of steel in sulfuric acid solutions. In addition, the inhibition efficiency increases with pyridinium salt concentration and temperature. The polarization curves show that both pyridinium salts are mixed-type inhibitors. Electrochemical impedance spectroscopy (EIS) indicates that charge transfer controls the corrosion process of steel in the absence and presence of compounds. The adsorption of each compound occurs via electrostatic and chemical bonds and obeys Langmuir’s adsorption isotherm. AFM images demonstrate that these salts protect this steel in H2SO4 solution. Theoretical calculations indicate a correlation between the experimental and quantum parameters.

The title benzimidazole compounds, namely, 2-(4-methoxynaphthalen-1-yl)-1H- benzo[d]imidazole, C18H14N2O(I) and 2-(4-methoxynaphthalen-1-yl)-1-[(4- methoxynaphthalen-1-yl)methyl]-1H-benzo[d]imidazole ethanol monosolvate, C 30H24 N2 O2 ·C2 H6 O(II), were synthesized by the condensation reaction of benzene-1,2-diamine with 4-methoxynaphthalene-1-carbaldehyde in the ratios 1:1 and 1:2, respectively. In I, the mean plane of the naphthalene ring system is inclined to that of the benzimidazole ring by 39.22 (8)° , while in II, the corresponding dihedral angle is 64.76 (6)° . This difference is probably influenced by the position of the second naphthalene ring system in II; it is inclined to the benzimidazole ring mean plane by 77.68 (6)° . The two naphthalene ring systems in II are inclined to one another by 75.58 (6)° . In the crystal of I, molecules are linked by N—H...N hydrogen bonds to form chains propagating along the a-axis direction. Inversion-related molecules are also linked by a C—H... interaction linking the chains to form layers lying parallel to the ac plane. In the crystal of II, the disordered ethanol molecule is linked to the molecule of II by an O—HN hydrogen bond. There are a number of C—H... interactions present, both intra- and intermolecular. Molecules related by an inversion centre are linked by C—H... interactions, forming a dimer. The dimers are linked by further C—H... interactions, forming ribbons propagating along the b-axis direction. The interatomic contacts in the crystal structures of both compounds were explored using Hirshfeld surface analysis. The molecular structures of I and II were determined by density functional theory (DFT) calculations at the M062X/6-311+g(d) level of theory and compared with the experimentally determined molecular structures in the solid state. Local and global reactivity descriptors were computed to predict the reactivity of the title compounds. Both compounds were shown to exhibit significant anticorrosion properties with respect to iron and copper.

The ability of (2-methoxy-2-oxoethyl)quinolinium bromide (Qui+ , Br- ) and (2-methoxy-2- oxoethyl) iso quinolinium bromide (isoQui + , Br- ) were investigated for corrosion inhibition of mild steel E24 in H2SO4 by impedance spectroscopy and potentiodynamic polarization measurements. A series of experiments with various inhibitor concentrations were conducted. The results show that the corrosion rate decreases, inhibition efficiencies increase, and surface coverage increase with increasing inhibitor concentration. Potentiostatic polarization revealed that both inhibitors affected cathodic and anodic reactions, making them inhibitors of a mixed type with a significant cathodic inhibitory character. Several adsorption isotherms, including Langmuir, Temkin, and Frumkin, were investigated to understand the inhibitor’s adsorption behaviour. The adsorption of both compounds on a mild steel surface obeys Langmuir’s adsorption isotherm. In addition, the values of showed a physisorption effect for the two prepared inhibitors. To compare the chemical reactivity of Qui + , Br- and isoQui+ , Br- and study the interactions between inhibitor molecules and the steel surface, different quantum chemical descriptors have been calculated, such as EHOMO, ELUMO, ΔE, χ, η, σ and ΔN. The results obtained reveal that the Qui+ , Br- has higher electronegativity (χ), global softness (σ), and global electrophilicity (ω) than the isoQui + , Br – compound. The order of IE determined from experimental measurements is successfully supported by theoretical analysis.

The title compound Schiff base (SB) named: (6E)-3-benzyloxy-6- [ [ [2‑hydroxy-1,1-bis(hydroxymethyl)ethyl] amino]methylene]cyclohexa-2,4‑dien-1-one(I) (C18 H21 N O5), was synthesized via the reaction of 4-benzyloxy- 2‑hydroxy-benzaldehyde with 2-amino-2-(hydroxymethyl)propane-1,3-diol (Trizma)and characterized by single- crystal diffraction XRD, infrared spectra, H and
1 13C NMR spectroscopy. It crystallizes as a zwitterion, (E)-5-
(benzyloxy)-2-(((1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)iminio)methyl)phenolate (II), with the phenolic H atom having migrated to the imino group. Additionally,Hirshfeld surface analysis (HS), two-dimensional fingerprint plots and energy frameworks of II were calculated to quantify the interatomic interactions present in the crystal.The antioxidant activity of the synthesized compound was evaluated by five tests: ABTS, DPPH, O- pH, SNP and reducing power activity. Furthermore, molecular docking calculations were performed for SB compound at the active site of mushroom tyrosinase (PDB ID:2Y9X) to determine the binding affinity between the title compound and receptor protein. Results reveal a great affinity (-6.16 kcal/mol) of the SB to the protein that is mainly dominated by hydrogen bonds. In this work, experimentally, the assessment of the anti-corrosion ability of this compound by different methods showed excellent inhibition. On the other hand, anti-corrosion potentials of title compound have been investigated using density functional theory (DFT) in gas and solvent phases. Chemical reactivity descriptors like global hardness (η), chemical potential (u), electronegativity (χ), electrophilicity (ω) and number of transferred electrons (ΔN) were computed at ωB97XD with 6–311+g(d) basis set. The local reactive sites on this compound were studied using Fukui indices, local philicity index and dual descriptor. The quantum chemical calculation suggests a good charge transfer tendency from the title compound to the low-lying vacant d-orbitals of iron (The average value of charge transfer is ΔNIII/Fe.≈ 2.21 and ΔNIII/Cu.≈ 0.07). The C7 atom is the nucleophilic sites (Δf(r)C7 ≈ 0.25) on the inhibitor for effective interaction on the metal surface as shown by local reactive descriptor in gas and solvent. Furthermore, the results obtained from DFT and TD-DFT studies are in excellent agreement with experimental data (structure geometry (RMS Error ≈ 0.3 Å), optical properties (λexp-Cal ≈18 nm) and inhibition efficiencies

[dimOHmIm]+,I- and [dimOHmBim]+,I- were investigated as a corrosion inhibitors for MS in 0.5 M H2SO4 using gravimetric, PDP and EIS techniques. Polarization curves
revealed that both compounds acted as mixed-type inhibitors, and that corrosion IE% increased with their higher concentrations. The adsorption of both inhibitors onto the MS surface obeyed Langmuir’s isotherm. The compound II showed a higher corrosion IE% than that of I. The quantum chemical calculations were applied to investigate the relationship between the two azolium salts derivatives electronic properties and their
corrosion IE%.
Keywords: imidazolium and benzimidazolium salts, MS, polarization, EIS, WL and corrosion inhibition.

PUNICA GRANATUM AS A NATURAL SOURCE OF CORROSION INHIBITOR FOR ZINC IN HYDROLIC ACID

VITIS VINIFERA L. SEEDS AS A SOURCE OF CORROSION INHIBITOR FOR ZINC AND ALUMINIUM

In this work, we studied the corrosion protection efficiency of three pyridinium salts on steel (API 5L Gr.B) in 0.5 M H2SO4 solution. Gravimetric and electrochemical methods were employed. We conducted investigations at various concentrations of the studied inhibitors and experiment temperature. The morphological of the steel surface was accomplished using scanning electron microscopy. Weight loss shows that an increase in the concentration of inhibitors A and C does not have any notable influence on the inhibition efficiency from 0.5 mM. However, the inhibition efficiency increases significantly with the increase of inhibitor B concentration. The values of (IE%) determined from EIS for these inhibitors follow the order: A ≈ C > B and the most excellent inhibition efficiencies are 97.88%, 86.96%, and 97.65%, respectively at 5 mM and all studied inhibitors are mixed-type inhibitors. In addition, the adsorption of the inhibitor molecules on the steel surface is reliable on the Langmuir adsorption isotherm model and the adsorption mechanism occurs through the combination of three aspects of interactions (physisorption, chemisorptions and retro-donation). IE% values of A, B and C inhibitors determined from EIS increase very slightly with temperature increase; the protective properties are excellent even at 55 °C (98.37% for A, 92.18% for B and 98.78% for C). This investigation is completed by a theoretical calculation of some quantum chemical parameters using the Gaussian09 program. The order of IE determined from experimental measurements is successfully supported by surfaces analysis and the obtained results confirmed an excellent concordance between potentiodynamic polarization, weight loss, EIS and theoretical study.

Keywords: Pyridinium saltsteelelectrochemical methodsweight losscorrosion

EFFECT OF PELARGONIUM GRAVEOLENS LEAVES EXTRACT ON ZINC CORROSION IN HYDROCHLORIC ACID