Electrochemical Deposition of γ-Phase Zinc-Nickel Alloys from Alkaline Solution

Abstract

Zinc-nickel alloys (γ-phase) with 8–15% nickel were electrochemically deposited onto stainless steel for increased corrosion protection. Alkaline deposition conditions were studied using ammonium hydroxide as the base source and a working pH range between 9.0–9.5. Sodium acetate was used as a complexing ligand and found to stabilize the metal ions in the electrolytic solution. Strongly adhering, quality deposits were obtained with room temperature electrodeposition. Uniform grain size and smooth deposits were observed with scanning electron microscopy, which lead to increased corrosion protection. X-ray diffraction and atomic absorption spectroscopy confirmed the deposits were γ-phase zinc-nickel with nickel content of 8–15% within the alloy. The corrosion potential for the γ-phase coatings was improved over that of pure zinc coatings by about 200 mV cathodic with respect to stainless steel but at a lower corrosion potential, thereby impeding the corrosion rate.