1997 Fiscal Year Final Research Report Summary
CHARACTERISTIC CURRENT DENSITY FOR ELECTRODEPOSITION OF ZINC AND ZINC ALLOYS.
| Project/Area Number |
08455348
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
FUKUSHIMA Hisaaki Kyushu University, Engineering professor, 工学部, 教授 (50038113)
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| Co-Investigator(Kenkyū-buntansha) |
OHUE Sstoshi Kyushu University, Engineering Research Associate, 工学部, 助手 (90264085)
OHGAI Takeshi Kyushu University, Engineering Research Associate, 工学部, 助手 (60253481)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Critical current density / Zinc / Cadmium / Manganese / Hydrogen / Hydroxide / Catalysis / Electrodeposition |
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| Research Abstract |
The minimum hydrogen overpotential on Al and Cd cathodes was reduced by the catalytic SCN^- ions in the solutions of low pH 1 and 2. The change in the magnitude of minimum hydrogen overpotential was less dependent on the concentration of SCN^- ions in Al cathode than Cd cathode. Moreover, the minimum hydrogen overpotential was not affected by the catalyst at higher pH 3,4 and 5 because the diffusion overpotential of hydrogen ions was predominant than other factors.
The critical current density of Zn was greatly increased in the solutions of lower pH.This was in good agreement with previously predicted Zn deposition mechanism. Since the pH buffering capacity of the sulfate solution increases considerably with decreasing pH of the solution below 2, larger hydrogen evolution rate is required to achieve the critical pH for Zn hydroxide formation. Therefore the higher critical current density was observed in the solutions of lower pH.
The critical current density was slightly increased in the SCN^- ion-containing solutions at low pH of 1 due to the reduction of minimum hydrogen overpotential by SCN^- ions and the current density was not changed by the catalyst in the solutions of high pHs probably because that the catalytic effect of SCN^- ions disappeared in the presence of Zn ions or Zn hydroxide.
The critical current density was increased with increasing the concentration of Cd ions in the solution, because the initial cathode surface was replaced by deposited Cd with high hydrogen over-potential and the hydrogen evolution rate was greatly reduced by Cd deposition at high current efficiency and the current density was not affected by the presence of less noble Mn than Zn in the solutions because the deposition potential of Mn was hardly attained at the equilibrium potential of Zn.
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