Process And Mechanism Of The Aqueous Solution Electrodeposition Of Zn-ni-re Alloys

In this thesis, the process of electrodeposition of Zn-Ni-RE alloy from aqueous solution and its mechanism of co-deposition have been discussed in detail. It covered the following aspects:Concluded from former researchers' work, electrodeposition of Rare Earth and rare-earth alloy from aqueous solution has been effected. Its mechanism has also been interpreted in theory. Therefore, electrodepostion of Zn-Ni-RE alloy from aqueous solution is possible. Meanwhile, complex chemistry of Rare Earth introduced in the solution to adjust electrode potential is a key issue for the process. In this process, a suitable complex chemistry has been attained.The solution's optimized composite and process' operating conditions have been determined. It was shown through research for electrodeposition of Zn-Ni-RE that different solution composite and different operating conditions can give rise to content of RE in coating. Main salt of RE is a most influential factor that affects content of RE in coating. Particularly it is shown that, only after concentration of main salt RE in solution succeeded a certain value, co-deposition of RE with Zn-Ni can be effected. Another interesting phenomenon is that addictive introduced into solution can greatly affect the content of RE in coating. Some other factors' influences to content of coating's composite have also been respectively shown.Zn-Ni-RE's anti-corrosion performance has been studied. The result is that Zn-Ni-RE coating's anti-corrosion performance is ideal even without being treated by chromate. In 5% sodium chloride neutral solution and under neutral salt spray, Zn-Ni-RE alloy coating's anti-corrosion is obviously better than Zn-Ni alloy coating with equal thickness.Mechanisms of Zn-Ni-Re's co-deposition have been discussed. Particularly, mechanism of "Rare Earth ion's deoxidization with auxiliary of cathode surface's additive's absorbates-formed layer" is put forward for the first time by the author, and, in order to explain this mechanism, a model of'electrical four layer' has been shown in detail from aspect of structure of cathode/solution's interface.