Effect of Cr3+ and SO42- on the Structure of Rust Layer Formed on Steels by Atmospheric Corrosion

    Published: Jan 2002

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    The effect of chromium ion (Cr3+) and sulfate ion (SO42-) on the structure of the rust layer formed by thin electrolyte-film corrosion of low-alloy steels has been examined. By using X-ray diffraction spectroscopy, it was found that coexistence of Cr3+ and SO42- in the electrolyte film covering the steel surface quickly forms the Cr-goethite (α-(Fe 1-X, CrX)OOH) layer which has been known as the final protective rust layer. Scanning vibrating electrode measurements showed that the rust layer formed under the electrolyte film containing Cr3+ and SO42- possesses higher protective ability against the aggressive chloride environment. Mössbauer spectroscopy revealed that most of the Cr-goethite formed by corrosion of the Fe-5at%Cr alloy under thin electrolyte-film containing SO42- was the superparamagnetic ultra-fine Cr-goethite. It can be said that the Cr-goethites possess the high protective ability against aggressive corrosives.


    atmospheric corrosion, electrolyte film, ion species, rust layer, goethite

    Author Information:

    Yamashita, M
    Associate Professor and Professor, Himeji Institute of Technology, Hyogo,

    Uchida, H
    Associate Professor and Professor, Himeji Institute of Technology, Hyogo,

    Cook, DC
    Professor, Old Dominion University, Norfolk, VA

    Committee/Subcommittee: G01.04

    DOI: 10.1520/STP10890S

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