Bronze disease

Bronze disease is the irreversible and nearly inexorable corrosion process occurring when chlorides come into contact with bronze or other copper-bearing alloys. It occurs as a dark green or a lighter fuzzy green coating on copper, bronze, and other copper-bearing alloys generally due either to contamination by salt water or after burial in dirt (as chloride salts are generally present in soil to some degree). If not treated, complete destruction of the affected artefact is possible. Transfer of chlorides from the contaminated artefact to other artefacts can spread the condition.