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 t(on)/t(off) 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 gamma-phase and the homogeneous and compact structure of the coatings. Chromating treatment can further improve the corrosion resistance of Zn-Ni coatings. (c) 2005 Elsevier B.V. All rights reserved.