2000 Fiscal Year Final Research Report Summary
Modification of Passive Film Formed on Environmental Materials by Photo Irradiation
| Project/Area Number |
11650742
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | Osaka University |
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Principal Investigator |
FUJIMOTO Shinji Osaka University, Graduate School of Engineering, Assistant Professor, 大学院・工学研究科, 講師 (70199371)
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| Co-Investigator(Kenkyū-buntansha) |
SHIBATA Toshio Osaka University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (90001205)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Passivity / Semiconductor / Photoelectrochemistry / Stainless Steel / Surface Modification / Corrosion and Protection / X-ray Photoelectron Spectroscopy / Quarts Micro Balance |
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| Research Abstract |
The Authors have reported that Cr enrichment in the passive film on Fe-Cr alloys and SUS304 stainless steel formed was enhanced by ultra-violet light irradiation in acid solution during passivation, resulting in an improvement of pitting corrosion resistance in chloride solutions. In the present work, similarly enhanced Cr enrichment was observed for SUS304 stainless steel in neutral solution, resulting in the improved pitting corrosion resistance. Electrochemical impedance spectroscopy revealed that the passive film has n-type semiconductor property and donor density was increased by photo irradiation. On the other hand, change in the electronic structure induced by separated electron and hole pair generated by photo transition was not observed. It is concluded that the modification was derived by recombination of electron and hole pair to release energy which generate point defects inside the passive film, which promote motion of ionic species inside passive film. Promoted motion, especially for Fe ions to be dissolved preferentially results in Cr enrichment in the passive film.
The effect of uv light irradiation on the atmospheric corrosion of pure Cu was also studied using quarts crystal micro-balance. The corrosion rate is influenced by temperature, oxygen partial pressure and humidity without uv light. When uv light is irradiated, the corrosion rate not necessarily depends on oxygen partial pressure. It is considered that activity of oxygen in the adsorption water layer is controlled by uv light to be constant.
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