Bronze is copper alloy. In modern times, bronze is an alloy of copper and any metal except zinc. It is generally more expensive than brass and more corrosion resistant. Bronze forms a patina (green color) which is protective to the metal and is often seen on artwork. Bronze will deteriorate rapidly if exposed to moisture and chlorides or sulfides.
This article was written by Anne Field, Extension Specialist, Emeritus, with references from Maryland Extension bulletin, Caring for Your Valuables: Brass, Copper, Pewter, Silver Tin.