On the akaganéite crystal structure, phase transformations and possible role in post-excavational corrosion of iron artifacts

The crystal structure of akaganéite and the akaganéite to hematite transition has been studied by means of conventional and synchrotron X-ray and neutron powder diffraction. The chemical formula of akaganéite can be written as FeO 0.833(OH) 1.167Cl 0.167. The crystal structure does not contain free...

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Bibliographic Details
Published in:Corrosion science 2003-11, Vol.45 (11), p.2563-2575
Main Authors: Ståhl, Kenny, Nielsen, Kurt, Jiang, Jianzhong, Lebech, Bente, Hanson, Jonathan C., Norby, Poul, van Lanschot, Jettie
Format: Article
Language:English
Subjects:
Applied sciences
Archaeological iron
B. Mössbauer spectroscopy
B. XRD
C. Exfoliation corrosion
Condensed matter: structure, mechanical and thermal properties
Corrosion
Corrosion environments
Exact sciences and technology
Inorganic compounds
Metals. Metallurgy
Physics
Structure of solids and liquids
crystallography
Structure of specific crystalline solids
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Summary:The crystal structure of akaganéite and the akaganéite to hematite transition has been studied by means of conventional and synchrotron X-ray and neutron powder diffraction. The chemical formula of akaganéite can be written as FeO 0.833(OH) 1.167Cl 0.167. The crystal structure does not contain free water. Heating below 200 °C will not alter the akaganéite structure. Initial water loss can be attributed to a large amount of adsorbed water due to a very small particle size; 0.15 μm by 0.03 μm. Chloride is released from the structure only in connection with the transformation to hematite. Due to its stability, the presence of akaganéite does not in itself posses a threat to iron artifacts, but it is rather a symptom of the presence of high concentrations of chloride in an acidic environment.
ISSN:0010-938X
1879-0496
DOI:10.1016/S0010-938X(03)00078-7