Ni 2+ and Mn 2+ ions have been added separately to the phosphate solution to minimize the porosity of the phosphate conversion coating on electrogalvanized steels. Results showed that the Ni 2+ or Mn 2+ in the solution reduced the grain size and porosity of the phosphate coating; thereby, the corrosion resistance was enhanced. However, Ni 2+ and Mn 2+ played a different role in the coating formation. Ni 2+ in the solution was reduced by Zn to form Ni, which enhanced the dissolution of Zn to promote the nucleation of hopeite grains. Mn 2+ in the solution facilitated the nucleation by increasing the impingement of reacting species.