Preparation And Microstructure Of Nano-crystalline Zn-ni Alloy By Jet Electrodeposition

Principle of corrosion resistance and deactivation about Jet electrodeposited (JED)nanocrystalline Zn-Ni alloys was studied in this paper. The effects of depositing parameters, such as electrolyte composition,jet speed, and current density on the morphology, chemical composition, phase composing, grain size and properties of Zn-Ni alloys were investigated. FMSEM and EDS were used to analyse the alloys'morphology and composition.The variation of Zn-Ni alloys'deposited phase structure with technical parameters was discussed by using X-ray diffraction analysis. The corrosion resistance and mechanical properties were measured by the electrochemical station and the microhardness tester. The experimental results show that:The range of the current density of JED as a high-speed electroplating technique with special flow characteristics, are enlarged largely owing to the promotion of plating solution. When the current density was 40A/dm~2,electrolyte flow rate was 3.33m/s, the deposition rate can be up to 47.33μm/min, which is 90 times faster or more than that of conventional electro deposition. And the current efficiencies are all over 80 %.Under the condition that temperature is 30°C, pH is 11.5,current density is 30 A/dm~2. Deposition grain size increases from 6.5 nm to 9.8 nm when the electrolyte flow rate increases from 0.83 m/s to 5.0 m/s. Samples of 7 nm nanocrystalline Zn-Ni alloys were produced by a double-refined technique of jet deposition combining with additive. When electrolyte flow rate was 3.33 m/s, Ni content was 13.6 %.Under the condition that temperature is 30°C, pH is 11.5, current density is 30 A/dm~2, when the current density increased, the zinc content in deposits decreased, the depositing rate increased, the current efficiency increased, the microhardness increased first and then decreased. When the current density is 40 A/dm~2, the microhardness can reach to its maximum of 334.92HV. When the current density increased from 20A/dm~2 to 40 A/dm~2, deposit formation was prone to (330) magnetization orientation, Under this experimental condition, after carrying on deactive processing, the alloy deposit formation electrode voltage increases from original - 0.796 V to - 0.623V.After seal processing the deactive deposit formation, the increasing scope of the electrode voltage was from - 0.796 V to - 0.512 V.