MECHANISM OF ANOMALY APPEARANCE IN ELECTRODEPOSITION OF ALLOYS FROM AQUEOUS SOLUTIONS.
| Project/Area Number |
62470057
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属精錬・金属化学
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
HIGASHI Kei KYUSHU UNIVERSITY, 工学部, 教授 (80037689)
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| Co-Investigator(Kenkyū-buntansha) |
AKIYAMA Tetsuya KYUSHU UNIVERSITY, 工学部, 助手 (10136517)
FUKUSHIMA Hisaaki KYUSHU UNIVERSITY, 工学部, 助教授 (50038113)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥6,600,000 (Direct Cost: ¥6,600,000)
Fiscal Year 1988: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1987: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Keywords | ELECTROPLATING / ALLOY DEPOSITION / ANOMALOUS CODEPOSITION / INDUCED CODEPOSITION / 共析機構 |
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| Research Abstract |
The electrodeposition behavior of the alloys where anomaly appeare is classified into the following two types; (a) induced codeposition in which reluctant metal deposits with inducing iron-group metal, (b)anomalous codeposition in which electrochemically less noble metal deposits more perferentially than noble iron-group metal. In present work, the electrodeposition precesses of the abnormal type alloys have been studied in terms of the electrochemical properties of iron-group metal, because iron-group metal is necessarily one of the constituent of the abnormal type alloy systems.
The mechanism of induced codeposition of Mo-iron-group metal alloys is proposed as follows. As preceding step in the alloy deposition process, molybadate ion adsorbs on cathode to depolarize the iron-group metal deposition and is reduced electrochemically to insoluble four valency Mo oxide. The lower Mo oxide can be reduced to metallic state by atomic hydrogen held on the freshly deposited iron-group metal using its unpaired electrons to form Mo-iron-group metal alloys.
The characteristic behavior of the anomalous electrodeposition of Zn-iron-group metal alloys is resulted from a further increase in the deposition overpotential of iron-group metal by occupying the discharge sites of iron-group metal with foreign substances. In the normal codeposition observed at low current density, the deposition behavior is reflected from nobility of the depositable elements to occur preferential deposition in the order of hydrogen, iron-group metal and Zn. At higher current density, the rise in pH due to an increase in the rate of hydrogen evolution make it possible to form Zn hydroxide and the deposition of iron-group metal is significantly polarized. On the other hand, Zn is reduced more easily from its hydroxide than the hydrated ion. Thus, the nobility defference between iron-group metal and Zn is canceled out, which results in the anomalous codeposition of Zn-iron-group metal system.
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Report
(3 results)
Research Products
(8 results)
