SYMPOSIA PAPER Published: 01 January 2002

Effect of Cr and SO on the Structure of Rust Layer Formed on Steels by Atmospheric Corrosion


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.

Author Information

Yamashita, M
Himeji Institute of Technology, Hyogo, Japan
Uchida, H
Himeji Institute of Technology, Hyogo, Japan
Cook, DC
Old Dominion University, Norfolk, VA
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Developed by Committee: G01
Pages: 149–156
DOI: 10.1520/STP10890S
ISBN-EB: 978-0-8031-5467-4
ISBN-13: 978-0-8031-2896-5