Nanoscale Analysis of [Steel/Ion] Reaction using SPring-8 Synchrotron Radiation

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Even if infrastructure is especially needed in the 21^<st> century, it becomes difficult to maintain steel structure forming infrastructure due to 高齢化・財政危機. However, corrosion protection for apparatus, steel structure, plant and traffic system costs as large as 4000 billion yen in Japan. It is really necessary now to 確保 long-term life for steel structure for reducing the maintenance cost which is now increasing every year, so that 国家使命 to restructure and reduce 経済負担 will be 戦略的に realized. For this purpose, we should 対応策を構築 by understanding basic of corrosion degradation occurred by correlation between corrosion species and steel materials.In this study, in order to understand corrosion degradation mechanism of steel materials, in situ observation of corrosion degradation and nano-structure analysis for corrosion product have been performed on steels using SPring-8 and Photon Factory synchrotron radiation X-rays. Reaction between iron ion and other alloying and environmental chemicals o … More n the steel surface and structure of corrosion product have been analyzed in terms of X-ray diffraction and X-ray absorption fine structure spectroscopies.By X-ray absorption fine structure measurements, we found that 1) Cr as an alloying element is in goethite, which decreases goethite crystal size and increase protective ability of rust layer of steel, 2) Ni ion dissolved from steel is in a certain site of akaganeite and/or spinel type oxide in rust layer and decreases corrosion reaction in the environment with chloride ion, 3) the relative amount of each iron oxide in rust changes with environmental condition and with amount of alloying element, 4) chloride ion in the environment affect the structure of rust layer.In situ observation of corrosion process on steels revealed that the ion species in electrolyte layer covering steel surface control the corrosion process and rust formation process. The rust formation processes of steels with different alloying contents were clarified by this in situ measurement.These results obtained in this study indicate that alloying elements and environmental ion species greatly affect the structure and protective ability of the rust layer formed on the steel surface. Less