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Underpotential Deposition of Zn in Presence of Iron-group Metals.

铁族金属存在下锌的欠电位沉积。

基本信息

批准号：
02650485
负责人：
AKIYAMA Tetsuya
金额：
$ 1.41万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02650485/
关键词：
Electroplating Alloy deposition Underpotential deposition Anomalous codeposition

项目摘要

Underpotential deposition of Zn in which Zn was codeposited at the potentials more positive than its equilibrium potential was found in the electrodeposition of Zn-Ni alloys from aqueous solutions. The underpotential deposition of Zn discussed in this study proceeded continuously with appreciable high rate, which was different from the so-called "underpotential deposition" reported in the previous papers. This phenomenon was observed only in the anomalous codeposition of Zniron-group metal systems such as Zn-Ni, Zn-Co and Zn-Fe but did not appear in the normal codeposition of Zn-Cu and Zn-Cd systems. The chemical states of the alloy constituents were investigated by XPS and Zn as well as Ni in the electrodeposits obtained in the underpotential region was found to be electroreduced to metallicstate.The underpotential deposition of Zn in the presence of iron-group metals was enhanced with an increase in temperature, a decrease in metal concentration ratio of in in the bath and the addition of chloride ion to the baths. Since it was known that these changes in the operating conditions diminished the inherent overpotential of iron-group metals, the underpotential deposition of Zn was related to the polarization behavior of iron-group metals during alloy deposition.Further, the microstructure of the alloys deposited at the underpotential region was investigated by X-ray diffraction technique. It was difficult that the mechanism of the underpotential deposition of Zn was explained in terms of the decrease in the activity of metallic Zn in the alloys.Consequently, since the underpotential deposition of Zn is observed in the anomalous codeposition of Zn-iron-group metal alloys, the mechanism of the underpotential deposition should be discussed in connection with that of the anomalous codeposition.

在Zn-Ni合金的电沉积过程中，发现了Zn的欠电位沉积，即Zn在比平衡电位正的电位下共沉积。本文所讨论的锌的欠电位沉积是以相当高的速率连续进行的，这与以往文献中所报道的所谓的“欠电位沉积”不同。这一现象只在Zn-Ni、Zn-Co、Zn-Fe等Zn-铁族金属体系的异常共沉积中观察到，而在Zn-Cu、Zn-Cd体系的正常共沉积中没有观察到。用XPS研究了合金成分的化学状态，发现在欠电位区获得的镀层中Zn和Ni都被电还原为金属态，在铁族金属存在下，Zn的欠电位沉积随温度的升高、镀液中In的金属浓度比的降低和Cl ~-的加入而增强。由于这些操作条件的改变降低了铁族金属固有的过电位，因此Zn的欠电位沉积与合金沉积过程中铁族金属的极化行为有关。用Zn在合金中的活度降低来解释Zn的欠电位沉积机理是困难的，因此，在Zn-铁族金属合金的异常共沉积中观察到Zn的欠电位沉积，因此，应结合异常共沉积机理来讨论Zn的欠电位沉积机理。