The term GREEN FILM ON THE STATUE OF LIBERTY is referring to the PATINA that has formed on the Statue of Liberty over time. PATINA is a thin layer of corrosion that forms on the surface of metals, and in this case it is a green film that has formed on the copper exterior of the Statue of Liberty. This PATINA is a result of oxidation, which occurs when copper is exposed to air and water. The PATINA helps protect the Statue of Liberty from further corrosion.