Does Copper Rust?
Copper does not rust because rust is iron oxide, and copper contains no iron. Instead of rusting, copper slowly reacts with air and moisture to form a surface layer that changes color over time. Fresh copper may darken to brown as copper oxides form, and with longer outdoor exposure it can develop a green or blue patina made of copper compounds.
That patina is usually protective and helps slow further corrosion, which is why copper is valued for roofing, gutters, plumbing, and electrical applications. In damp or contaminated environments, copper can still corrode more quickly and may show green staining where water runs or pools. If you see reddish rust like spots on copper, it is often from iron particles or steel fasteners nearby rather than the copper itself.
