Cling film residue can be one of the hardest substances to remove from metal, especially if the metal is porous. Luckily, there are many ways to remove stubborn cling film residue from all types of metals.
Wrap the blade of the putty knife in a damp cleaning rag. Scrape as much of the cling film residue from the metal as possible. Take care not to scrape the metal itself if possible.
Soak the corner of a cleaning rag in nail polish remover. Rub the nail polish remover over the cling film to remove it from the metal. You may have to work at the plastic for several minutes if the cling film is stuck on tightly or covers a large area of the metal.
Spray an automotive spray lubricant over the plastic on the metal and allow it to sit for about five or 10 minutes. Wipe away the spray lubricant residue from the metal to remove traces of cling film residue. You may have to use pressure to peel away the plastic.
Dip the corner of a rag into rubbing alcohol. Rub the surface of the metal with the alcohol to remove plastic that is stubbornly stuck to the metal. Use a firm rubbing motion to remove the cling film residue from the metal surface.
Heat the metal in the oven or on the stove if possible. This will soften the plastic and make it easier to scrape off. Scrape away as much of the softened plastic with a putty knife. Sprinkle baking soda over the cling film. Rub a damp cloth over the baking soda residue to remove any traces of cling film.
Place a few dabs of petroleum jelly over the plastic on the metal. Allow the jelly to sit for about five minutes. Wipe away the jelly with a paper towel. Some of the cling film should also wipe away along with the petroleum jelly residue.
Scrub any remaining plastic on the metal with a scrub pad or steel wool. This will remove all remaining traces of the cling film residue from the surface of the metal.
Wash the metal with washing up liquid to remove all residues from the plastic removal process.