Verdigris

Part of speech: noun (n.)

1. A green poisonous substance used as a pigment and drug, obtained by the action of acetic acid on copper, and consisting essentially of a complex mixture of several basic copper acetates.

2. The green rust formed on copper. [Colloq.]

Part of speech: verb (v.)

To cover, or coat, with verdigris. [R.] "An old verdigrised brass bugle." Hawthorne.