Cosmoline

Cosmoline is the trade name for a generic class of rust preventatives, conforming to MIL-C-11796C Class 3, that are a yellowish, light-amber, or greenish colored ointment-like mass; have a slight fluorescence; and have a petroleum-like odor and taste. Cosmoline is similar to petroleum jelly in properties, appearance, and thickness. It is the purified residue obtained from the distillation of petroleum oils.

Chemically, cosmoline is a homogeneous mixture of oily and waxy long-chain, non-polar hydrocarbons. It can range in color from white to yellow, and can differ in viscosity and shear strength. Cosmoline melts at 113–125 °F (45–52 °C) and has a flashpoint of 365 °F (185 °C).

Its most common use is in the storage and preservation of firearms. Previously, cosmoline was used to preserve other items. Objects the size of entire vehicles could be preserved for future use with cosmoline.

During World War II, US gun crews serving the huge coastal artillery batteries were known as "Cosmoliners" because they were tasked with the near constant application of cosmoline to the guns.