Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating

Electroless nickel-phosphorus (Ni-P) plating is a widely used surface treatment method due to its excellent corrosion and wear resistance properties. However, the inertness of copper to hypophosphite oxidation necessitates a palladium activation process for the preparation of Ni-P coating on copper. In this study, we present a convenient approach for the deposition of a cobalt layer on copper using galvanic replacement, facilitated by the special complexing ability of iodide. The results demonstrated that the actual potential of copper could be adjusted to be lower than that of cobalt in a solution containing 8 mol/L NaI, enabling the deposition of a cobalt layer on copper in 15 minutes at 90°C. Furthermore, the deposition rate of the cobalt layer was found to increase with the concentration of CoCl₂ in the NaI solution. Importantly, the Ni-P coating obtained through cobalt layer activation exhibited morphology, structure, and corrosion resistance, friction resistance similar to the Ni-P coating obtained using the common palladium activation. Therefore, the cobalt layer prepared on copper through galvanic replacement may serve as a viable alternative to palladium for activating electroless Ni-P plating.