Electrodeposition of Co-P Coatings Reinforced by MoS₂ + Y₂O₃ Hybrid Ceramic Nanoparticles for Corrosion-Resistant Applications: Influences of Operational Parameters

During recent decades, Co-P alloy deposits have gained enormous attention primarily owing to their favorable tribomechanical properties; therefore, they are regarded as a potential alternative to hard chromium coatings. The previous works on these systems usually addressed the approaches to improve their tribomechanical characteristics. However, to increase the industrial applications, especially in marine environments, enhancement of corrosion performance should also be considered. The focus of this investigation is improving the corrosion properties of Co-P deposits through the incorporation of hybrid nanoparticles, i.e., MoS₂ and Y₂O₃, as well as controlling the applied current density. Microstructural and morphological aspects of the coatings were characterized by XRD, EDS, FE-SEM, and AFM. While the surface morphology of the Co-P alloy deposit contains several surface defects, MoS₂ + Y₂O₃ reinforced ones are compact and composed of nodular grains. Although there is no change in morphology of the nodular grains with current density variation, the surface roughness increases by increasing the current density from 15 to 25 A dm⁻². Influences of both nanoparticle loadings in the electrolyte and the applied current density on the corrosion performance of the deposits are addressed in detail. Overall, the results confirmed that the Co-P-4 g/L MoS₂ + Y₂O₃ nanocomposite coating electrodeposited at 25 A dm⁻² has the highest corrosion resistance against 3.5 pct NaCl solution, ≈ 10 times higher than that of Co-P.