Oshikawa Wataru

写真a

Title

Professor

Researcher Number(JSPS Kakenhi)

80224228
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Current Affiliation Organization 【 display / non-display 】

  • Duty   University of the Ryukyus   Faculty of Engineering   School of Engineering_Energy and Environment Program   Professor  

  • Concurrently   University of the Ryukyus   Graduate School of Engineering and Science   Material,Structural and Energy Engineering   Professor  

  • Concurrently   University of the Ryukyus   Graduate School of Engineering and Science   Solid Mechanics and Materials Engineering   Professor  

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Academic degree 【 display / non-display 】

  • The University of Tokyo -  Doctor of Engineering

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External Career 【 display / non-display 】

  • 2005.07
    　
    　

     

  • 2005.07
    　
    　

    - , University of the Ryukyus, Faculty of Engineering, Department of Mechanical Systems Engineering, Engineering Materials,Design and Processing, Associate Professor  

  • 2005.07
    　
    　

    University of the Ryukyus, Faculty of Engineering, Energy and Environment Program, Professor  

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Research Areas 【 display / non-display 】

  • Nanotechnology/Materials / Material processing and microstructure control

  • Nanotechnology/Materials / Material processing and microstructure control

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Published Papers 【 display / non-display 】

  • Study on Initial Corrosion Behavior of Arc‑thermally Spray Zn, Zn–Al, and Al–Mg Coatings Exposed in Atmospheric Environment for One‑Year

    Atsuhi Nakano, Yuki Toyota, Chihiro Morita, Kentaro Yasui, Wataru Oshikawa, Noboru Yonezawa

    International Journal of Steel Structures     2024.09 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

  • Effect of Diffusion Rate of Oxygen on Soil Corrosion and Evaluation of that in Soil

    Fujihashi Kenta, Nakagami Ryosuke, Oshikawa Wataru

    Zairyo-to-Kankyo ( Japan Society of Corrosion Engineering )  73 ( 8 ) 200 - 209   2024.08

    Type of publication: Research paper (scientific journal)

    　View Summary

    <p>Soil corrosion rate for architecture and civil engineering is regarded as 0.02 mm/year regardless of the soil. However, it is considered that corrosion rates of each soil are different because soil properties such as particle size, water content, chemical composition and pH are different. In this study, we measured dissolved oxygen diffusion coefficient of each soil and each water content and evaluated the charge transfer resistance of each dissolved oxygen concentration by AC impedance method, to investigate the effect of dissolved oxygen diffusion on soil corrosion.</p><p>It was suggested that major oxygen diffusion path in soil is air that dispersed into soil. As a result, dissolved oxygen diffusion coefficient was correlated with air-filled porosity. It is suggested that the corrosion rate in soil increase with increase of air-filled porosity (decrease of water content) in case of considering not metal-water interface surface area.</p>

  • Effect of Diffusion Rate of Oxygen on Soil Corrosion and Evaluation of that in Soil

      73 ( 8 ) 200 - 209   2024.08 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

  • Color Tone of Corrosion Products and Estimation of Rust Composition by Image Processing

    Fujihashi Kenta, Oshikawa Wataru

    Tetsu-to-Hagane ( The Iron and Steel Institute of Japan )  110 ( 15 ) 1225 - 1236   2024

    Type of publication: Research paper (scientific journal)

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    <p>Appropriate maintenance and maintenance of infrastructures that has been used for a long time is required because there is the concern that safety will deteriorate due to atmospheric corrosion. However, the cost of maintenance and management is also increasing, and there is required to save labor and improve efficiency of maintenance and management. Therefore, the purpose of this study was to easily estimate the rust composition by the image processing of image of steel surface corroded by the outdoor exposure test. The outdoor exposure test was conducted in Choshi City and those conditions were open exposure and shelter exposure for 2.5 years. The compositions of those corrosion products measured by X-ray diffraction. Exposed test pieces were photographed RAW with the digital camera. Those photographs were developed and trimmed. The obtained images were converted from RGB images to La*b* and LCh images. The histograms of hue were fitted to the Gaussian function to determine the peak position and the spread of the histogram. As a result, it was indicated that the peak position shown in the histogram of hue shifted to the low-angle side due to the increase in FeFe<sub>2</sub>O<sub>4</sub>. In addition, it was indicated that the composition ratio of α-FeOOH, β-FeOOH, γ-FeOOH and FeFe<sub>2</sub>O<sub>4</sub> can be estimated by the shape, spread and peak position of the histogram of hue. As shown in the graphical abstract, the composition ratio of the corrosion products measured by RIR method and estimated by image processing was in good agreement.</p>

  • Effect of Soil Particle Diameter on Soil Corrosion

    Fujihashi Kenta, Nakagami Ryosuke, Oshikawa Wataru

    Zairyo-to-Kankyo ( Japan Society of Corrosion Engineering )  72 ( 1 ) 22 - 30   2023.01

    Type of publication: Research paper (scientific journal)

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    <p>The main foundation structure of photovoltaic power generation facilities is a steel pile foundation. Soil corrosion rate is regarded as 0.02 mm/year regardless of the soil. However, it is considered that corrosion rates of each soil are difference. In this study, we estimated the soil corrosion environment by measuring the physical properties of soil and evaluated the charge transfer resistance of each soil environment by AC impedance method that regarded soil as electrolyte, in order to investigate the effect of soil particle size on soil corrosion.</p><p>Glass beads of uniform sphere haven't been packed close-packed structure, and porosity of soil with particle size distribution was nearly equal to regardless of particle size. But in case of the soil that included particles less than 50μm in a large quantity, porosity of the soil was increase. Porosity of soil that had similar particle size distribution was nearly equal regardless of water content. Therefore, it is suggested that the change of soil water content was replacement liquid phase and gas phase. The charge transfer resistance of soil corrosion decreased with decrease of gas phase ratio in soil. Therefore, it is suggested that the charge transfer resistance of soil corrosion might be estimated from the soil particle size distribution and water content.</p>

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