i think the protection you seek is a farday cage - could be wrong !

Faraday cage can't work the object needs to be isolated air tight meaning no air molecules are allowed in!

Once it is sealed with a non conductive isolator and made air tight a faraday cage or any metal cage will do as the electrons are trapped above the isolation and conducted trough the metal or copper cage....

But a copper cage in open air without any isolator surrounding the item you wan't to protect won't do.