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

Abstract

Zinc-nickel alloys with 8-15% nickel were deposited onto stainless steel for corrosion protection. Alkaline deposition conditions were utilized given that alkaline systems have been found to offer superior substrate coverage which results in better corrosion protection of the metal substrate (stainless steel) compared to acid bath depositions. This method utilizes ammonium hydroxide as the base source with a working pH range of 9-9.5. Sodium acetate was used as the complexing ligand as it was found to stabilize the metal ions in the electrolytic solution. Strongly adhering, quality deposits were obtained with electrodeposition at room temperature. Bath compositions and applied potential had an effect on morphology of the films as seen in scanning electron microscopy. Upon examination by x-ray diffraction and atomic absorption spectroscopy, all deposits were confirmed as γ phase zinc-nickel alloys with a nickel content of 8-15%. The corrosion potential for the γ-phase coatings was improved over the pure zinc coatings.

Electrodeposited Zinc-Nickel Nanocomposite Coatings

“…PRC and PRP are similar to PC and PP as a cathodic pulse is applied but during the off times, an anodic pulse is applied to the electrode. Previous studies show an increase in incorporation of particles through a pulse deposition method with better overall coverage of the underlying material compared to a constant applied potential technique [7,45,48,57,62,68,[78][79][80]. The nanoparticles are incorporated in a higher percentage because of the partial dissolution of the metal deposit during the anodic pulse.…”

“…6H 2 O, 120 g/L KCl, 100 g/L NH 4 Cl, 30 g/L NaCH 3 Momeni et al [14] Hardness, antibacterial properties Gomes et al [40,41] 0 [50,55,[59][60][61]. The γ-phase and δ-phase are predominantly formed through electrochemical methods, with γ-phase showing the strongest protection against corrosion [57,60,[62][63][64][65]. Zinc nickel γ-phase alloys with approximately 8-18% have been found to be optimal for maximum corrosion protection [48,57,62,65].…”

“…The γ-phase and δ-phase are predominantly formed through electrochemical methods, with γ-phase showing the strongest protection against corrosion [57,60,[62][63][64][65]. Zinc nickel γ-phase alloys with approximately 8-18% have been found to be optimal for maximum corrosion protection [48,57,62,65].…”

“…Zinc-nickel alloy formation follows an anomalous deposition mechanism which occurs when the electrochemically less noble metal deposits preferentially to the more noble metal. This is verified through examination of the voltammetry patterns of the zinc-nickel system as the individual zinc and nickel reduction peaks are shifted based on the presence of the other metal species in solution [48,59,62,70,[72][73][74]. During deposition, a thin layer of nickel is initially deposited onto the substrate.…”

“…Though the bulk of the work has been done under acidic conditions, focus of the research may benefit from pushing into the realm of alkaline deposition as throughout literature, optimal coating formation is realized under alkaline conditions. Although zinc-nickel coatings deposited under acidic conditions tend to have a higher current efficiency, alkaline processes tend to lead to better substrate coverage [12,57,62,79]. A drawback of alkaline conditions is stabilizing agents are needed to keep the metal species from precipitating as metal hydroxides from the solution.…”