Дослідження осадження та корозійної поведінки сплавів CO-Ni в умовах, наближених до середовища цементного каменю

Abstract. Problem. The application of protective coatings is one of the most effective ways to improve the durability of structural materials, especially under aggressive environmental conditions. Among these materials, steel reinforcement used in construction is of particular interest due to its prolonged exposure to the alkaline environment of cement stone. Under such operating conditions, reinforcement requires reliable corrosion protection, which makes the study of new coatings with enhanced protective properties highly relevant. The Co–Ni system is considered promising due to its ability to form durable, wear-resistant, and corrosion-resistant coatings.Previous studies have shown that electrochemical deposition of Co–Ni alloys from citrate electrolytes allows for control over the microstructure and composition of the coatings by adjusting process parameters. In particular, the cathodic current density plays a key role in determining the phase composition, grain size, coating density, and corrosion resistance. However, despite available publications, the optimization of deposition conditions to achieve maximum protective performance in alkaline environments remains an open question. Methodology. The study was conducted by electrodepositing Co–Ni coatings in galvanostatic mode using a citrate-based electrolyte. The cathodic current density was varied within the range of 2–12 A/dm². The chemical composition of the coatings was determined by spectral analysis, the microstructure was analyzed using scanning electron microscopy, and corrosion resistance was evaluated through testing in a 0.1 M NaOH solution, with calculation of the corrosion depth rate. Originality .It was found that increasing the cathodic current density up to 12 A/dm² led to a rise in cobalt content in the alloy up to 31%. However, the best coating properties were observed at a current density of 6–8 A/dm². Under these conditions, bright, dense, fine-crystalline coatings were formed with a high current efficiency of up to 84%. The corrosion depth rate was only 0.005–0.015 mm/year, indicating high protective performance. However, a further increase in cobalt content led to decreased corrosion resistance due to the reduced stability of the passive film. Pulse plating was recommended to improve homogeneity and reduce porosity. The obtained results confirm the feasibility of using Co–Ni coatings for the long-term protection of steel reinforcement operating in the alkaline environment of cement stone. The application of optimized current parameters and process improvements significantly enhances the effectiveness of corrosion protection.