Portugaliae
Electrochimica Acta

The corrosion inhibition efficiency of a new benzimidazole derivative, namely, 1-decyl-2-[(5-methylisoxazol-2-yl)methyl]benzimidazole (DIB) for carbon steel in 1 M hydrochloric acid (HCl) was studied by EIS and PDP electrochemical methods. The results indicate that DIB reduces carbon steel corrosion rate in the corrosive medium, and its inhibition efficiency increased with the concentrations. The polarization data indicate that DIB is of a mixed type. EIS study reveals that DIB is adsorbed onto the corroding metal surface, creating a barrier between the acid and carbon steel. The DIB molecules adsorption fitted into Langmuir adsorption isotherm. Furthermore, DIB electronic properties that correlate to its corrosion inhibitory such as EHOMO, ELUMO, energy gap (∆E), dipole moment (µ), electronegativity (), global hardness () and the fraction of electrons transferred from DIB molecule to the metallic atom (∆N), were calculated in PCM solvent at the B3LYP/6-311+G (d, p) level of theory. The theoretical results are in good agreement with the observed corrosion inhibition efficiency of the tilted compound.

The electro-oxidation of 4-amino-3-methyl-1,2,4-triazole-5-thione (MTSNH) on a bronze substrate in an alkaline methanol solution produces a homogeneous polymer film. The formation kinetics of the film was investigated using cyclic voltammetry, chronoamperommetry and electrochemical impedance spectroscopy. Cyclic voltammograms indicated that the polymer film (pMTSNH) was formed anodically between -350 and 350 mV/SCE. During the second cycle, the oxidation peak of the monomer disappeared, indicating the formation of the insulating film. We have also shown that the monomer oxidation reaction is essentially irreversible and controlled by a diffusion process. The inhibition efficiency of this polymer was determined by potentiodynamic polarization and electrochemical impedance spectroscopy in a 3.5% NaCl solution.

The inhibition performance of twenty-five amino acids and related compounds was studied by theoretical techniques. The effect of the acidic solution was considered on the molecular dynamics simulation, and the calculated binding energies for most of the inhibitors was ˃100 kcal mol−1, suggesting chemisorptive interactions. Density Functional Theory (B3LYP/6-31G*) quantum substance chemical study was utilized to discover the upgraded geometry of the inhibitors. Also, a linear quantitative structure-activity relationship (QSAR) model was built by Genetic Function Approximation (GFA) method, to run the regression analysis and build up connections between various descriptors and the experimental inhibition efficiencies. The prediction of corrosion efficiencies of these inhibitors nicely matched the experimental measurements. The statistical parameters are: 0.973421, which indicates that the model was excellent. The proposed model has great dependability, strength, and consistency on checking, with inward and outside approval.

In this paper, we report on the preparation of an amorphous and nanocrystalline structure of titanium dioxide, by cathodic electrodeposition on fluorine doped tin dioxide (FTO) coated glass, from an aqueous peroxo-titanium complex solution. Structural X-ray analysis shows anatase phase for heated deposits, and an amorphous form for non-heated deposits. Scanning electron microscopy (SEM) allowed investigating the morphological aspect of the deposits which exhibited nano-particulate grain size. AFM results exhibited the different roughness values of both kinds of films. The crystalline deposits have been used as catalysts for the photocatalytic oxidation of methyl orange dye, under an irradiation source (UV lamp of 365 nm). The results revealed that the dye has undergone a slight degradation under UV illumination. Using spectrophotometer measurements, the decolourisation rate was estimated from residual concentration.

Certain N, O, S-ligating ring compounds and thioureas were investigated to understand their role of copper corrosion inhibition in acetonitrile. For 5 quinones under study, including xanthone, xanthene, thioxanthone, acridone and 1,4-naphthoquinone, acridone was the best inhibitor, with Cu corrosion rate of 4.495 × 10-4 mm/year, whereas 1,4-naphthoquinone exhibited the lowest inhibition, due to a lower number of nitrogen groups. With the presence of sulphur, to form a stronger bond with Cu, thioureas had better inhibiting behavior than quinones. Of 4 thioureas, namely thiourea (tu), diphenylthiourea (dptu), phenylthiourea (ptu), and ethylenethiourea (etu), the fourth shows the highest inhibition – with Cu corrosion rate of 2.27 × 10-4 mm/year – and the third shows the lowest one, due to the steric effect from the phenyl group. When halide ions are present, the inhibition efficiency of thioureas decreases, due to more preferable Cu complexation to halides; the strongest copper-halide bond formation occurred by the freest iodide ion, which is consistent with the results from X-ray crystallography and electrochemistry.