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Effect of Cr and SO on the Structure of Rust Layer Formed on Steels by Atmospheric Corrosion
Yamashita M, Uchida H, Cook DC


Pages: 8    Published: Jan 2002


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Source: STP1421-EB


Abstract
The effect of chromium ion (Cr) and sulfate ion (SO) 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 Cr and SO in the electrolyte film covering the steel surface quickly forms the Cr-goethite (-(Fe , Cr)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 Cr and SO 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 SO was the superparamagnetic ultra-fine Cr-goethite. It can be said that the Cr-goethites possess the high protective ability against aggressive corrosives.


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

Paper ID: STP10890S
Committee/Subcommittee: G01.04
DOI: 10.1520/STP10890S
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