Editing Copper (section)

===Chemical===
[[File:Copper wire comparison.JPG|left|upright=0.7|thumb|Unoxidized copper wire (left) and oxidized copper wire (right)]]
[[File:Royal Observatory Edinburgh East Tower 2010 cropped.jpg|thumb|The East Tower of the [[Royal Observatory, Edinburgh]], showing the contrast between the refurbished copper installed in 2010 and the green color of the original 1894 copper]]
Copper does not react with water, but it does slowly react with atmospheric oxygen to form a layer of brown-black copper oxide which, unlike the [[rust]] that forms on iron in moist air, protects the underlying metal from further corrosion ([[passivation (chemistry)|passivation]]). A green layer of [[verdigris]] (copper carbonate) can often be seen on old copper structures, such as the roofing of many older buildings<ref name="Grieken-2005">{{Cite book|url=https://books.google.com/books?id=3qL3vfUZHMYC|title=Cultural Heritage Conservation and Environmental Impact Assessment by Non-Destructive Testing and Micro-Analysis|last1=Grieken|first1=Rene van|last2=Janssens|first2=Koen|date=2005|publisher=CRC Press|isbn=978-0-203-97078-2|page=197|language=en}}</ref> and the [[Statue of Liberty]].<ref>{{cite web|title=Copper.org: Education: Statue of Liberty: Reclothing the First Lady of Metals – Repair Concerns|url=http://www.copper.org/education/liberty/liberty_reclothed1.html|work=Copper.org|access-date=11 April 2011}}</ref> Copper [[tarnish]]es when exposed to some [[sulfur]] compounds, with which it reacts to form various [[copper sulfide]]s.<ref>{{cite journal|last1=Rickett|first1=B. I.|last2=Payer|first2=J. H.|title=Composition of Copper Tarnish Products Formed in Moist Air with Trace Levels of Pollutant Gas: Hydrogen Sulfide and Sulfur Dioxide/Hydrogen Sulfide|journal=Journal of the Electrochemical Society|date=1995|volume=142|issue=11|pages=3723–3728|doi=10.1149/1.2048404|bibcode=1995JElS..142.3723R}}</ref>