Sergiy A. Korniy

Environmentally friendly anticorrosion additive based on the natural mineral montmorillonite enriched with calcium cations were obtained by liquid-phase ion exchange. It was established that the degree of enrichment of the mineral with calcium cations exceeded 3 wt% and depended on the concentration of the calcium acetate solution. Electrochemical methods established that the addition of the modified mineral (2 g/l) into a model chloride-containing porous concrete solution (pH=12) provided an inhibitory efficiency of steel protection used in almost 95% production of reinforcement. The protection mechanism is based on the controlled release of calcium cations, which maintains high alkalinity of the surface layer and promotes the formation of a dense passive film on the steel surface. According to SEM/EDX analysis, the presence of the additive reduces the chloride content on the steel surface from 3.5 to 0.07 wt%, preventing pitting. The results obtained confirm the prospects of calcium-enriched montmorillonite as an additive to the concrete mix to prolong the service life of reinforced concrete structures in aggressive conditions.

This study reports the development of smart‐release anti‐corrosion pigments based on ion‐exchanged montmorillonite (MMT) for the protection of high‐strength AA2024 aluminium alloy. Zn ²⁺ ‐ and Mn ²⁺ ‐modified MMTs were synthesized by liquid‐phase ion exchange. XRD and SEM/EDX confirmed the preservation of the montmorillonite structure and incorporation of the modifying cations. The inhibiting performance of the pigments was evaluated in acid rain using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and gravimetric measurements. Zn‐modified MMT provided the highest protection, reducing the corrosion current density from 1.2 × 10 ⁻⁶ to 7.9 × 10 ⁻⁸ A cm ⁻² after 168 h and achieving inhibition efficiencies of 93.4%, 93.7%, and 91.8% by polarization, EIS, and gravimetric measurements, respectively. Mn‐modified MMT showed lower inhibition efficiency (47%–54%), whereas Zn–Mn‐modified systems provided intermediate protection (75%–90%). The superior performance of Zn‐MMT may be associated with the release of Zn ^{2 +} cations from montmorillonite interlayers and their possible interaction with OH ⁻ ions generated during cathodic oxygen reduction. These processes may favor the formation of sparingly soluble zinc‐containing species, potentially including Zn(OH) ₂ , which could contribute to the development of a protective surface layer and reduce the electrochemically active area. Zn‐modified MMT therefore shows strong potential as an environmentally safe inhibiting pigment for anti‐corrosion coatings.

The surface of g-C3N4 was modified with polar hydroxyl groups through g-C3N4 treating with an aqueous solution of hydrogen peroxide in an ultrasonic (US) field. The diffraction patterns showed a shift of the diffraction peaks corresponding to the (002) plane for modified g-C3N4 samples towards larger values of 2θ angles (from 27.3 to 27.4°) compared to un¬modified g-C3N4, which indicated a decrease in the interlayer distance of the photocatalysts (from 0.3266 to 0.3254 nm) and, accordingly, an increased rate of charge carrier transfer. Scanning electron microscopy and energy-dispersive X-ray analysis confirmed an increase in the content of hydroxyl groups on the g-C3N4 surface with increasing the duration of US treatment. The chemical structure of modified g-C3N4 was evaluated by Fourier transform infrared spectroscopy. A significant decrease in the absorption intensity in the range of 3000–3400 cm–1 was found with US treatment duration of 60 min, which can be ex¬plained by possible exfoliation of g-C3N4 layers and fracture of interlayer hydrogen bonds, oxidation of hydroxyl groups on the g-C3N4 surface to carboxyl groups, or “screening” of hydroxyl groups due to steric hindrance.

The method of obtaining walnut shell extract was developed. Gravimetric and electrochemical methods of investigation established that the extract exhibited inhibitory properties of 20 steel in tap water, citric and hydrochloric acids. In the temperature range of 298–333 K, maximum corrosion protection is observed in 5% HCl at a temperature of 313 K, which may be associated with the hydrolysis of glycosidic bonds in an acidic environment and a corresponding change in the nature of adsorption processes. In the studied media, the inhibitor inhibits both partial electrode reactions. The calculated activation energy values indicate that the energy factor influences its anti-corrosion effect. The decrease in surface tension, angular angles and increase of thermodynamic work of adhesion with increasing inhibitor concentration in the studied media confirms its surface activity.

Homogeneous oxygen-containing Ni–Mo coatings were electrodeposited and evaluated as cathodes for the hydrogen evolution reaction in alkaline media. SEM, EDX, and profilometry were used to analyze morphology, composition, and surface roughness. The electrodeposition current density strongly controlled the incorporation of Mo and O, resulting in non-monotonic compositional changes and a pronounced evolution of surface morphology from compact to highly developed microgrooved structures.The coatings exhibit high HER activity in 1.0 M KOH, with overpotentials of 0.130–0.160 V at 100 mA/cm2 and Tafel slopes of 0.083–0.109 V/dec. The kinetic analysis suggests a mixed Volmer–Heyrovsky mechanism under non-ideal surface conditions. The coating containing 41.56 wt% Mo and 9.22 wt% O delivers the optimal catalytic performance, with an overpotential ~3.5 times lower than previously reported for Ni–Mo-based coatings with a comparable chemical composition. These findings are consistent with previous reports indicating that the optimal oxygen content in Ni–Mo electrocatalysts does not exceed ~10 wt%, beyond which catalytic activity deteriorates.Overall, the results show that electrodeposition parameters effectively tune composition and morphology and highlight the key role of controlled oxygen incorporation in enhancing HER performance, providing a basis for developing efficient Ni–Mo cathodes for alkaline hydrogen production.

The effect of non-isothermal heating and chemical modification on the structural state and corrosion resistance of amorphous Co72Fe5Si11B12 and Co70Fe2.5Cr4.5Si11B12 cobalt alloys in 1 M aqueous potassium hydroxide solution is investigated. During heating of the Co72Fe5Si11B12 alloy, significant surface changes occur, in particular the formation of crystalline phases and oxidation, which is accompanied by a decrease in the rate of corrosion pro¬cesses. Heat treatment at temperatures of 773–787 K helps to increase the corrosion resistance of the material in an alkaline environment. It is found that the amorphous Co70Fe2.5Cr4.5Si11B12 alloy is characterized by higher corrosion resistance compared to the alloy without chromium addition. Thermal modification of the alloy with Cr content causes a shift of corrosion potentials in the positive direction, however it is accompa¬nied by an increase in corrosion currents. It is found that increase in the potential sweep rate does not significantly affect the values of corrosion potentials, but leads to an increase in corrosion currents in contact with an aggressive environment.