Atmospheric corrosion of copper and the colour, structure and composition of natural patinas on copper

FitzGerald, K. P., Nairn, J., Skennerton, G. and Atrens, A. (2006) Atmospheric corrosion of copper and the colour, structure and composition of natural patinas on copper. Corrosion Science, 48 9: 2480-2509.


Author FitzGerald, K. P.
Nairn, J.
Skennerton, G.
Atrens, A.
Title Atmospheric corrosion of copper and the colour, structure and composition of natural patinas on copper
Journal name Corrosion Science   Check publisher's open access policy
ISSN 0010-938X
Publication date 2006-09
Sub-type Article (original research)
DOI 10.1016/j.corsci.2005.09.011
Volume 48
Issue 9
Start page 2480
End page 2509
Total pages 30
Editor G. T. Burstein
Place of publication United Kingdom
Publisher Pergamon
Collection year 2006
Language eng
Subject C1
291403 Alloy Materials
671004 Castings
0912 Materials Engineering
Abstract This paper describes the results of atmospheric corrosion testing and of an examination of patina samples from Brisbane, Denmark, Sweden, France, USA and Austria. The aim was threefold: (1) to determine the structure of natural patinas and to relate their structure to their appearance in service and to the atmospheric corrosion of copper; (2) to understand why a brown rust coloured layer forms on the surface of some copper patinas; (3) to understand why some patinas are still black in colour despite being of significant age. During the atmospheric corrosion of copper, a two-layer patina forms on the copper surface. Cuprite is the initial corrosion product and cuprite is always the patina layer in contact with the copper. The growth laws describing patina formation indicate that the decreasing corrosion rate with increasing exposure time is due to the protective nature of the cuprite layer. The green patinas were typically characterised by an outer layer of brochantite, which forms as individual crystals on the surface of the cuprite layer, probably by a precipitation reaction from an aqueous surface layer on the cuprite layer. Natural patinas come in a variety of colours. The colour is controlled by the amount of the patina and its chemical composition. Thin patinas containing predominantly cuprite were black. If the patina was sufficiently thick, and the [Fe]/[Cu] ratio was low, then the patina was green, whereas if the [Fe]/[Cu] ratio was approximately 10 at%, then the patina is rust brown in colour. The iron was in solid solution in the brochantite, which might be designated as a (copper/iron) hydroxysulphate. In the brown patinas examined, the iron was distributed predominately in the outermost part of the patina. (c) 2005 Elsevier Ltd. All rights reserved.
Keyword Materials Science, Multidisciplinary
Metallurgy & Metallurgical Engineering
Atmospheric Corrosion
Copper
Patina
Holistic Model
Australia
Exposure
Aerosol
Runoff
Q-Index Code C1

 
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