Maksym Danylchuk

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.

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 heat treatment on the development of micromechanical and tribocorrosion properties of electrodeposited Ni–Mo–B coatings was examined. The Ni–Mo–B coatings were electrodeposited onto low-carbon steel from a citrate electrolyte containing amorphous boron. Isothermal annealing was performed at 950°C for 2 hours in an argon atmosphere. The coatings were analyzed using SEM/EDS, XRD, dynamic nanoindentation, and tribocorrosion tests in a 3% NaCl solution. It was found that heat treatment induces a diffusion transformation of amorphous boron into a matrix-filled composite consisting of a Ni(Mo) solid solution and strengthening phases (Ni3B and Mo2NiB2). Increasing the Mo content from 8 to 16 wt.% resulted in a 3.75-fold increase in the Mo2NiB2 ternary boride phase. This structural change led to a significant increase in microhardness (up to 11.67 GPa) and the elastic modulus (292.5 GPa). In tribocorrosion tests, the coating with 16 wt.% Mo demonstrated better stability: the wear track width decreased by 46%, and the coefficient of friction remained more consistent (around 0.2) compared to the coating with 8 wt.% Mo. Additionally, increasing boride phase content shifted the wear mechanism from oxidative-adhesive with microdeformation to a mixed process, with oxidative wear dominating. The study shows that high-temperature annealing of Ni–Mo–B coatings enhances their phase composition by forming complex borides. Coatings containing 16 wt.% molybdenum offer improved resistance to mechanical and corrosion damage, making them suitable for oil and gas, chemical, and utilities industries.

Homogeneous, defect-free Ni–Mo coatings with excellent corrosion resistance and catalytic activity for the HER in alkaline media were obtained by electrodeposition. SEM, EDX, and profilometry were used to characterize morphology, composition, and surface roughness. The coating containing 41.56 wt% Mo and 9.22 wt% O demonstrates an optimal combination of high electrocatalytic activity (η₁₀₀ mA/cm2 = 0.140 V, j₀ = 0.059 A/cm2) and corrosion resistance (icorr = 0.0037 mA/cm2). The increased oxygen content promotes the formation of a surface with a high specific area and a large number of active sites for the hydrogen evolution reaction. The results obtained provide a scientific basis for the development of Ni–Mo electrode materials suitable for the efficient electrolytic production of “green” hydrogen.

Ni–Mo–B coatings with 7–27 wt.% Mo and 0.75–1.36 wt.% B were synthesized electrochemically. SEM, EDX, and titrimetric analyses were revealed their morphology and composition. Corrosion resistance in 1.0 M KOH slightly decreased with higher Mo due to anodic dissolution, yet remained low (0.0035–0.0084 mA/cm²). Catalytic activity depended on Mo content; the best catalyst showed 0.194 V overpotential at 100 mA/cm². Hydrogen evolution followed the Volmer–Heyrovsky mechanism, confirming these coatings’ potential for green hydrogen production.

Corrosion-resistant Ni-Mo-B electrodeposited coatings were produced from a self-regulating suspension electrolyte, and the effect of deposition parameters on their composition, structure, and properties was examined. The coatings exhibit a fine-grained structure, contain 8–27 wt.% Mo and 1.30–3.39 wt.% B, and are free of pores and cracks. An increase in molybdenum content improves corrosion resistance in chloride media. Micromechanical properties were evaluated using scratch testing and nanoindentation, while tribological and tribocorrosion behavior was studied using a “plane–ball” scheme in air and in 3% NaCl solution. It was established that coatings with 8 wt.% Mo are more effective under dry friction, whereas coatings with 16 wt.% Mo perform better under tribocorrosion loading. Ni-Mo-B coatings are considered as an environmentally friendly alternative to hard chromium.

Ni–Mo coatings on steel substrates made of complex self-regulating electrolytes were obtained by the electrodeposition method. The surface morphology and elemental composition of the obtained coatings were determined by the methods of electron microscopy and energy dispersive analysis. The maximum molybdenum content (25.26 mass%) was obtained at a deposition current density of 0.5 A/dm2 (pH 9.2, 300 rpm, 22±2°С). The thickness of such coatings is 15–20 mm. The microhardness of coatings increases with an increase in the molybdenum content. The proposed electrolyte is characterized by high stability and is technologically and environmentally friendly.