1995 Fiscal Year Final Research Report Summary
Study on Cathodic Protection with Illumination by TiO2 Coating
| Project/Area Number |
06452324
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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 |
Structural/Functional materials
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TSUJIKAWA Shigeo The University of Tokyo, School & Faculty of Enineering, Department of Metallurgy, Professor, 大学院・工学系研究科, 教授 (20011166)
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| Co-Investigator(Kenkyū-buntansha) |
SHINOHARA Tadasahi The University of Tokyo, School & Faculty of Engineering, Department of Metallur, 大学院・工学系研究科, 助教授 (70187376)
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| Project Period (FY) |
1994 – 1995
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| Keywords | semiconductor electrode / semiconductor oxide / titanium oxide (TiO2) / cathodic protection / photoelectrochemistry / sol-gel method |
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| Research Abstract |
The optimum heat treatment temperature for cathodic protection of stainless steel is 250ﾟC,at which the specimen with TiO2 coating exhibits the least noble photopotential, <-500mV.SCE.Photopotential becomes nobler when heat treatment temperature is higher than 300ﾟC,because Fe, Cr and Ni in the stailess steel diffuse into the coating in the coating process. The potential of the illuminated specimen with the optimum heat treatment temperature, 250ﾟC,remains relatively less noble potential, -200--300mV.SCE,even under the dark condition-this effect is called as "photo memory effect" and specific behavior for the stainless steel coated by the sol-gel method.
The optimum heat treatment temperature range for cathodic protection of Cu is from 600 to 700ﾟC,in which Cu specimen with TiO2 coating exhibits the least noble photopotential. Copper oxide seemed to be formed in the coating process and had an obvious p-type photo-effect for the specimens treated below 600ﾟC.Cathodic treatment at-600mV c
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an eliminate the photo-effect of copper oxide, which even can make the TiO2 coating exhibit photo-effect on the Cu substrate below the critical temperature. Given the proper heat treatment condition, the TiO2 coating effectively protects Cu from corrosion in 0.3% NaCl solution over the pH range from 4 to 12 under illumination, because the photopotentials in both deaerated and aerated solutions are driven into the immunity domain in the E-pH diagram of Cu by the TiO2 coating.
The photo-electrochemical behavior of TiO2/steel system was investigated. It was found that the noble photopotential for the steel directly coated with TiO2 resulted from the diffusion of Fe into the coating in the coating process. An Fe oxide layr at the TiO2-steel interface can retard this diffusion and greatly improve the photo-response of TiO2/steel. Under high temperature (>500ﾟC) treatment for TiO2 coating, Fe diffusion was observed even in the presence of Fe oxide layr and was responsible for the noble photopotential. Amongst various forms of Fe oxides, alpha-Fe203 was considered to be important for obtaining the less noble photopotential while the property change of alpha-Fe203 with oxidation temperature was shown to influence the photo-effect of TiO2/steel. Less
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Research Products
(12 results)
