How to Clean Cosmoline

Meg Jernigan

Cosmoline is a viscous petroleum distillate used as a corrosion preventative and surface protectant. It has a consistency similar to petroleum jelly and is formulated to adhere to nearly any surface even under extremely high or low temperatures and prolonged exposure to water. Cosmoline was used by the military for long-term protection of vehicles and firearms, and it's used in marine and agricultural settings to prevent the rusting of components exposed to harsh conditions. Removing Cosmoline can be a challenge because it's so tenacious. Follow the steps in this guideline to clean Cosmoline from any material.

  1. Disassemble the item to be cleaned as necessary to reach internal areas. Items as large as trucks were frequently dipped in molten Cosmoline so that it would penetrate as much as possible.

  2. Mineral Spirits
  3. Soak small metallic parts in a bucket of mineral spirits. Wipe the Cosmoline away with rags or small brushes. Repeat as needed until the part is clean.

  4. Wipe down larger metal items with a rag dampened with mineral spirits. Replace the rag if it becomes saturated with Cosmoline.

  5. Bore Mop
  6. Use a cleaning rod and fabric bore mop inside firearm barrels. Saturate the mop with mineral spirits and clean or change it frequently until all the Cosmoline is removed.

  7. Heat non-metallic items, such wood or rigid plastic, in your oven at its lowest temperature to liquefy the Cosmoline. Don't allow the temperature to reach over 150 degrees. Remove the item and wipe it with a rag, and repeat the process as needed to remove most of the Cosmoline.

  8. Murphy Oil Soap
  9. Use a mild detergent solution or oil soap on a rag or brush to remove the final traces of Cosmoline from non-metallic items.