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The Role of Rusts in Corrosion and Corrosion Protection of Iron and Steel

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Title: The Role of Rusts in Corrosion and Corrosion Protection of Iron and Steel
Authors: Tamura, Hiroki Browse this author
Keywords: Iron
Low alloy steel
Modeling studies
Atmospheric corrosion
Issue Date: Jul-2008
Publisher: Pergamon
Journal Title: Corrosion Science
Volume: 50
Issue: 7
Start Page: 1872
End Page: 1883
Publisher DOI: 10.1016/j.corsci.2008.03.008
Abstract: The processes of atmospheric corrosion of iron and steel and the properties of corrosion products (rusts) are modeled based on a quantitative evaluation of the chemical reactions pertaining to corrosion to elucidate the conditions with which corrosion-protective rust films form. Based on the model, it is suggested that in the initial stage of corrosion, in the rusts, the pH of the aquatic system is maintained at 9.31 owing to an equilibrium with iron(II) hydroxide and the rate of air-oxidation at this pH is very fast, and that dense, self-repairing rust films form, protecting the underlying iron and steel. However, after corrosion stops, the rust film deteriorates due to the dissolution and shrinkage by aging, and the deteriorated rust film separates the anode and cathode reaction products (Fe2+ and OH- ions) to cause crevice corrosion. The air-oxidation of iron(II) in anode channels without the presence of OH- ions results in strongly acidic solutions (pH 1.41), causing acid corrosion. It is proposed that good catalysts (e.g. copper(II) and phosphate ions) accelerate the air-oxidation at low pH, delaying the crevice- and acid-corrosion stages. Further, it is argued that iron compounds with negative charges due to the non-stoichiometric proportions of the lattice oxide ions and metal ions (solid oxoanions of iron) exhibit stable cation-selective permeability even with a drop in pH. Rust films including such compounds would stop the passage of aggressive anions and act to protect iron and steel.
Type: article (author version)
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 田村 紘基

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