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Message:: [QUOTE="BadThad, post: 2351122, member: 17261"]Verdigris is ANY type of copper corrosion. I hate the term "bronze disease", it's not a disease, it's copper corrosion and, therefore, verdigris. The reason the term BD even exists is due to ignorance by the non-scientific populace. Verdigris and BD are one in the same. Verdigris is a very complicated mixture often dominated in composition by the anionic element most prevalent in the environment it was exposed to (i.e. chloride, sulfate, acetate, etc). Also, time, temperature, pressure and other external influences alter the composition - as we see with ancient coins. Often, the verdigris can be converted into a hard, crystalline mineral with a high Mohs index, as someone else pointed out in this thread. At that point, it should no longer be referred to as verdigris, it is not, it is technically mineral. As far as verdigris forming a protective layer, it is true. Once an object is completely covered, the reactive copper sites become essentially inaccessible to fresh anion attack. However, the corrosion process is still active on a micro-scale as it is dynamic depending on many environmental factors (i.e. temperature, humidity, etc). Verdigris is quite complicated on a electrochemical scale! This is most evident with chloride ion where a somewhat self-perpetuating reaction occurs with the constant formation of fresh hydrochloric acid.[/QUOTE]