Mariia Olena Danyliak

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 acid-activated montmorillonite was obtained through modification with etidronic acid, and its inhibitory properties for protection of an aluminium alloy in an acid rain environment were investigated. It was established that acid activation does not destroy the montmorillonite structure; however, it leads to an increase in the interlayer spacing to 1.58–1.62 nm and a decrease in the intensity of the basal (001) reflection by XRD analysis. These changes are attributed to ion exchange between the protons of etidronic acid and the native exchangeable cations of montmorillonite, as well as to increased hydration of the clay structure. The presence of the main structure-forming elements of the mineral and a reduction in the content of exchangeable cations as a result of acid activation was confirmed by EDX analysis. The inhibitory efficiency of the activated montmorillonite for corrosion protection of the aluminium alloy was determined to reach 88.78 %. It was shown that, after 30 days of exposure, the corrosion rate decreases by approximately nine times compared with the control sample. It was shown that the surface of the aluminum alloy, after 30 days of exposure to acid rain in the absence of montmorillonite, was completely corroded due to the development of non-uniform corrosion. In contrast, the alloy surface exposed in the presence of activated montmorillonite contained only a small amount of corrosion products. The protective mechanism is associated with the adsorption of phosphonate anions on the alloy surface and the formation of a protective barrier layer as a result of complexation. The obtained results demonstrated the potential of acid-activated montmorillonite as an environmentally friendly anticorrosion pigment for the protection of aluminium alloys under atmospheric conditions.

The effect of mechanical pressing on the electrochemical behavior of a magnesium anode in a chloride-free electrolyte was investigated. Magnesium is a promising material for Mg-air batteries; however, its practical application is limited by surface passivation and intensive localized corrosion. It is established by SEM/EDX analysis that pressing alters surface morphology and increases the oxide fraction. An increase in the anodic activity of pressed magnesium was established by potentiodynamic and potentiostatic studies. After polarization, corrosion products con are identified on the surface. The results indicate that mechanical pressing improves the conditions for anodic dissolution of magnesium and the performance of magnesium anodes in metal-air electrochemical power sources.

An eco-friendly anti-corrosion pigment for protective coatings was obtained by mechanochemical modification of natural montmorillonite with zinc monophosphate. The intercalation of zinc cations (~5 wt%) and phosphate anions (~4 wt%) in montmorillonite structure was confirmed by EDX analysis. It was established that the modification contributes to partial amorphization of the structure and an increase in the interplanar distance from 1.54 to 1.58 nm. According to the results of potentiodynamic studies, it was established that the inhibitory efficiency of the obtained pigment on the aluminium alloy in an acid rain environment exceeded 95%. It was shown by the electrochemical impedance spect¬roscopy method that the introduction of 20 wt% of the obtained modified montmorillonite into the epoxy coating on the alloy increased its protective properties by more than 2 orders of magnitude. The protective effect occurred due to the gradual release of active ions and the formation of layers of zinc hydroxide and aluminium phosphate on the alloy surface. The use of the mechanochemical modification allows the inhibitors to be encapsulated in the montmorillonite structure, which guarantees their long-term protective effect in polymer coatings on aluminium alloys due to the gradual release effect.

The Ti–20Nb–20Zr β-rich titanium alloy for medical applications obtained by electron beam casting was studied. According to electrochemical studies in simulated body fluid (Hank’s solution), it was found that the Ti–20Nb–20Zr alloy had better anti-corrosion properties (higher corrosion potential and lower corrosion current) than widely used alloys such as commercially pure Ti, Ti–6Al–4V and Ti–6Al–3Nb–2Zr alloys. The main corrosion mechanisms of the studied alloys in Hank’s solution were considered and the influence of the phase-structural state on their electrochemical behavior was assessed