Targeted surface modification of Cu/Zn/Ag coatings and Ag/Cu particles based on sacrificial element selection by electrodeposition and redox replacement

The electrodeposition-redox replacement (EDRR) method was investigated for the preparation of two types of functional surfaces. A synthetic solution simulating Zn process solution containing 65 g/L Zn, 200 ppm Cu, 2 ppm Ag and 10 g/L H₂SO₄ was used as the source for creating functional surfaces EDRR experiments. The effects of operating parameters such as deposition potential (E₁), deposition time (t₁), and redox replacement time (t₂) have been comprehensively studied. When E₁ was selected to deposit Zn as the sacrificial metal, coherent Cu/Zn/Ag coatings with various chemical compositions, crystalline phases and surface morphology were obtained depending on the selected t₁ and t₂. The Cu/Zn/Ag coatings also exhibited competitive corrosion resistance (E_corr = −683 to −634 mV vs. Hg/Hg₂SO₄, j_corr = 1.6–4.1 μA/cm²) when compared to those detailed in the literature. In contrast, when E₁ was selected so that Cu was the sacrificial metal, separated Cu/Ag particles with controllable chemical composition, particle size (82–170 nm) and tunable surface plasmon resonance (SPR) behavior were formed through the variation of t₁ and t₂. In addition to the ability to tailor different functionalities for the surfaces from the same solutions, the process was performed in a single electrochemical cell without the addition of any complexing agents. Overall, these promising results demonstrated the versatility of the EDRR method to create various high value-added functional materials from complex hydrometallurgical solutions which contain multiple metal impurities.