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https://www.howtocleanstuff.net/how-to-clean-antique-copper-and-bronze/
Yes, it can be cleaned but...
The patina that has formed actually protects the copper. Probably best to leave it alone- it will eventually turn green again.
Would be extremely expensive to clean- scaffolding, collection of the runoff chemicals.
And once it gets through the brown stage the green is actually an attractive look.