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Name: Tim
Status: other
Grade: other
Location: VA
Country: USA
Date: Fall 2009



Question:
If copper is left outside in the weather before it is installed, can the weather affect the strength of the copper? I realize that it can make the copper change color, is this also am indicator of possible future corrosion?


Replies:
Hi Tim,

When copper is left out in the elements, it develops a very thin, complex layer of (often brightly colored) copper oxides, copper carbonates and copper sulfate, on its surface. These protect the underlying metal from further corrosion. This surface corrosion layer is responsible for the color you are seeing, not changes in the underlying copper itself. The strength of the copper that lies under this surface layer is utterly unaffected because the extremely thin surface corrosion layer protects the base metal. The color you see is not an indicator of future corrosion; it simply indicates the presence of a thin layer of surface corrosion that acts very effectively to prevent the bulk of the copper below from destructive corrosion and damage.

Regards,
Bob Wilson


The green color (called patina) is a surface corrosion, but it does not greatly affect the structural strength of the copper.

Vince Calder



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