Structure of corrosion film formed on copper exposed to controlled corrosive environment

This paper describes a transmission electron microscopy (TEM) investigation of copper coupons exposed to a corrosive mixed flowing gas environment (MFG). A focused ion beam (FIB) liftout technique was used to extract electron transparent specimens for TEM investigation. A duplex corrosion film comprising cuprite (Cu₂O) and chalcocite (Cu₂S) developed on the copper substrate. The oxide demonstrated a dense morphology with evidence of chlorine in the oxide layer showing that chlorine plays an important role in the corrosion of copper transforming the protective Cu₂O layer to a non-protective layer. The outer layer of the Cu₂S demonstrated a porous morphology allowing easy penetration of water and gases.