Corrosion behavior of pulse-plated Zn-Ni alloy coatings on AZ91 magnesium alloy in alkaline solutions

Zn-Ni alloy coatings were plated on AZ91 magnesium alloy using a pulse potential electrodeposition method after zinc immersion and Zn-Cu plating. The density and frequency of electric current, deposition time and ton / toff have large effects on chemical composition, thickness of the Zn-Ni coatings. The Zn-Ni coatings provide very good corrosion protective function to inner AZ91 magnesium alloy. The good corrosion resistance of Zn-Ni coatings is attributed to the existence of the γ-phase and the homogeneous and compact structure of the coatings. Chromating treatment can further improve the corrosion resistance of Zn-Ni coatings.