Structural and corrosion protection properties of electrochemically deposited nano-sized Zn–Ni alloy coatings

Highlights: • Nano-sized, compact and bright deposits were obtained galvanostatically. • Deposition of zinc–nickel alloys has been materialized in domination of zinc-rich ∂-(Ni₃Zn₂₂) and γ-(Ni₅Zn₂₂) phases. • Sodium citrate (Na₃C₆H₅O₇) has been used together with boric acid (H₃BO₃) for inhibition of instantaneous deposition of zinc and accordingly increasing the relative amount of nickel. • Corrosion protection performances of the deposits were increased with increasing deposition current density and nickel amount. • Crystal defects have been increased with decreasing crystallite size. - Abstract: Zn–Ni alloy coatings were fabricated galvanostatically by applying varied current densities from 10 to 30 mA cm⁻². Surface morphology of the coatings was examined with SEM. Crystal structure of the coatings was studied with X-ray diffraction spectroscopy (XRD). Compositions of the coatings were determined by atomic absorption spectroscopy (AAS). Corrosion protection properties studied using open circuit potential (OCP) measurements, potentiodynamic polarization measurements (Tafel), electrochemical impedance spectroscopy (EIS). Deposited alloy coatings were compact and nano-sized. Crystallite sizes of the coatings were varying from 26 nm to 36 nm. Nickel content of the samples were increased by increasing current densities and varied from 6.7 to 18.9 wt.%. Best corrosion protection performance was seen on the sample obtained at 30 mA cm⁻². Our results are considerably encouraging for protection of mild steel against corrosion by obtained Zn–Ni alloys