| Composite electrodeposits technology has developed in recent years as a novel method for surface strengthening. Ni-ZrO2 composite coating with good wearability, high strength and erosion resistance can be obtained by this method through adding nanometer zirconia in nickel-based electrolyte. To get fine electrodeposits, it is necessary to prepare a homogeneous and stable composite suspension.Nano-ZrO2 was used to prepare composite electroplating bath by adjusting pH value of solution and adding different kinds of dispersants such as PEG with simple structure and MZN with complex structure. Characters of the composite electroplating bath under various experimental conditions, including comparing with those of the aqueous solution, were studied by Zeta potential technique, absorbency measurements, sedimentation experiments, particle-size analysis and TEM observation. It was found that Nano-ZrO2 could not suspend in bath by adjusting pH value only or adding general dispersant like PEG which was regular approaches used in water. However, MZN, a kind of dispersant with many complex branched chains, which could not only adsorb tightly on the surface of the particles but also prevent falling off from the surface with the effect of electrolytic ions, made the particles in composite bath separate from each other by a mechanism of steric hindrance role. MZN was used in the experiment as an effective dispersant. The influence of the percent of MZN, adding order, mixing time and pH value on the stability of the suspension was investigated. As a result, a homogeneous and stable composite suspension were obtained through adding electrolytes in stable zirconia suspension at pH=3 and following mill mixing 3 hours. Using the electrolytes prepared by above conditions, composite coating quality was greatly improved.
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