Hot-dip galvanization with pulse-electrodeposited nickel pre-coatings

The galvanizing process whereby steel is electrodeposited with nickel using pulsed current waveforms and hot-dipped in a molten zinc bath at 450 °C is investigated here as a potential route to mitigate the coating overgrowth problem. The influences of processing parameters, including electroplating and galvanizing durations, on the evolutions of microstructure and phase structures, and polarization characteristics of galvanized steels are explored. The results from the polarization study and salt spray tests indicate that the galvanized coating prepared with a nickel pre-coating, comprising zinc–nickel intermetallic layers, exhibits significantly better corrosion resistance than the conventionally-galvanized steel.

Research highlights
► Galvanized coatings with a uniform, void-free structure are prepared with pulsed-current electrodeposited nickel interlayer.
► Hot-dip and electrodeposition durations are crucial for the fabrication of galvanized coatings containing nickel interlayer.
► Galvanized coatings comprising of Zn–Ni intermediate layers exhibit considerably high resistance to red rust formation compared to the conventionally-galvanized steel.
► The Zn–Ni intermediate layers are characterized by low corrosion rates and high corrosion potentials.