Copper metal corrosion occurs because metals copper (Cu). Born to lose an electron to become Cu2 +, which are blue, and when you get electrons into Ag + to become Ag (silver metal) under the copper sheet metal.
Copper, the metal is corroded copper (Cu) the electrons become Cu2 +, which are blue and when Ag + ions to become Ag (silver), the island is a copper plaque.
Copper metal, however the corrosion because of copper metal (Cu). The loss of electrons become Cu2 which are blue and when Ag receive electrons in will become Ag (silver) on the sheet metal copper.