| Project/Area Number |
06555211
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 試験 |
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| Research Field |
Material processing/treatments
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| Research Institution | Osaka University |
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Principal Investigator |
SHIBATA Toshio Osaka University, Faculty of Engineering, Professor, 工学部, 教授 (90001205)
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| Co-Investigator(Kenkyū-buntansha) |
OHNAKA Noriyuki Hitachi, Ltd, Hitachi Laboratory, Senior Researcher, 日立研究所, 主任研究員
HARUNA Takumi Osaka University, Faculty of Engineering, Research Associate, 工学部, 助手 (70243186)
FUJIMOTO Shinji Osaka University, Faculty of Engineering, Assistant Professor, 工学部, 講師 (70199371)
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| Project Period (FY) |
1994 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥13,300,000 (Direct Cost: ¥13,300,000)
Fiscal Year 1996: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1995: ¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 1994: ¥9,000,000 (Direct Cost: ¥9,000,000)
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| Keywords | stainless steel / photoelectrochemical response / semi conductor / passive film / He-Cd Laser / ultra-violet light / pitting corrosion / birth and death stochastic process / 光電気化学 / レーザー / 表面解析 / 熱活性化 / 局部腐食 / 半導体電極 / 環境材料 / 耐食性 / 走査レーザー電解顕微鏡 |
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| Research Abstract |
Photo electrochemical response has been applied as a poweful in-situ characterization technique for the passive film on the metals and alloys. However, the effect of the light exposure on the corrosion behavior has been open to discussion. In this study, Type304 stainless steel immersed in 3.5% NaCl was exposed with ultra-violet light to improve pitting corrosion resistance in the same media. uv light of 325 nm in wave-length generated by He-Cd laser was used as light source with output power of 35 mW and the exposure area of 6 mm in diameter. The pitting potential, which is an index for pitting corrosion resistance, was shifted for about 80 mV after uv light exposure during film formation period prior to pitting corrosion test. The improvement of pitting corrosion resistance depends on the light intensity. In the range of the light available in this study, a most suitable intensity was observed.
The pitting corrosion induction period at a constant applied potential was also measured and analyzed with the birth and death stochastic probability process for various applied potentials to obtain the generation and repassivation rate of pitting corrosion. The generation rate, gamma, was lowered by a factor about 6 after exposure of uv light during passivation. On the other hand, the uv exposure during pitting corrosion generation period leads to almost no change on mu, the repassivation rate. The exposure during pitting corrosion generation affects only very small improvement on lambda and mu.
The X-ray photo electron spectroscopy revealed that the chromium in the passive film, which is known to improve the corrosion resistant of stainless steels, is enriched after an exposure of uv light. Therefore the uv exposure was confirmed to improve the self healing ability of stainless steel, which is obtained by chromium enrichment in the film.
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