Copper alloy is an alloy made of copper and other metals or non-metals melting, and its surface acidification treatment is to prevent other active metals from rusting, such as: Fe+H2SO4 = FeSO4 ten H2↑. It's stable when it produces ferrite. It's a chemical change. The surface passivation treatment is a physical change, which is to grind away the Angle of the surface with a grinding wheel.