The Korean Society of Surface Science and Engineering

In this study, we developed and evaluated a multilayer nickel/zinc-nickel (Ni/Zn-Ni) coating using a single electrodeposition bath with controlled potential. Traditional zinc-nickel coatings offer superior corrosion resistance compared to pure zinc, particularly with an optimal Ni composition of 12-15 wt.%. However, we utilized a pulse-reverse potential (PRP) technique to create multi layers of Zn-Ni alloy and pure Ni. Linear sweep voltammetry (LSV) was employed to determine appropriate potential ranges for selective Zn-Ni alloy and Ni layer electrodeposition. The coating microstructure was analyzed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). X-ray diffraction (XRD) revealed γ-phase Zn-Ni alloy in both direct current (DC) and PRP samples, but additional Ni phase was found in case of PRP. Corrosion resistance was evaluated using potentiodynamic polarization in 3.5 wt.% NaCl solution, where PRP coatings exhibited significantly lower galvanic couple current density and higher couple potential, demonstrating improved corrosion resistance compared to the DC case. Additionally, Vickers hardness testing indicated that the PRP coating had higher surface hardness than DC case. This Ni/Zn-Ni multilayer approach shows potential as a robust anti-corrosion solution, offering enhanced mechanical properties and corrosion resistance.

Keywords Zn-Ni alloy; Nickel; Electrodeposition; Multi-layer; Pulse-reverse potential