WD 40

WD-40 is the trademark name of a United States-made water-displacing spray. It was developed in 1953 by Norm Larsen, founder of the Rocket Chemical Company, San Diego, California. It was originally designed to repel water and prevent corrosion,[1] and later was found to have numerous household uses.

WD-40 stands for "Water Displacement – 40th Attempt". Larsen was attempting to concoct a formula to prevent corrosion in nuclear missiles, by displacing the standing water that causes it. He claims he arrived at a successful formula on his 40th attempt.[1] WD-40 is primarily composed of various hydrocarbons.

WD-40 was first used by Convair to protect the outer skin of the Atlas missile from rust and corrosion.[1][2] The product first became commercially available on store shelves in San Diego in 1958.[1]

Function
The long-term active ingredient is a non-volatile, viscous oil which remains on the surface, providing lubrication and protection from moisture. This is diluted with a volatile hydrocarbon to give a low viscosity fluid which can be sprayed and thus penetrate crevices. The volatile hydrocarbon then evaporates, leaving the oil behind. A propellant (originally a low-molecular weight hydrocarbon, now carbon dioxide) provides gas pressure in the can to force the liquid through the spray nozzle, then itself diffuses away.

These properties make the product useful in both home and commercial fields; lubricating and loosening joints and hinges, removing dirt and residue, and extricating stuck screws and bolts are common usages. The product also may be useful in displacing moisture, as this is its original purpose and design intent. [edit]

Formulation
WD-40's formula is a trade secret. The product is not patented to avoid completely disclosing its ingredients.[2][3] WD-40's main ingredients, according to U.S. Material Safety Data Sheet information, are:

51% Stoddard solvent (i.e., mineral spirits: primarily hexane, somewhat similar to kerosene) 25% Liquefied petroleum gas (presumably as a propellant; carbon dioxide is now used instead to reduce WD-40's considerable flammability) 15+% Mineral oil (light lubricating oil) 10-% Inert ingredients

The German version of the mandatory EU safety sheet lists the following safety-relevant ingredients:

60–80% Heavy Naphtha (petroleum product), hydrogen treated 1–5% Carbon dioxide

It further lists flammability and effects to the human skin when repeatedly exposed to WD-40 as risks when using WD-40. Nitrile rubber gloves and safety glasses should be used. Water is unsuitable for extinguishing burning WD-40.

There is a popular urban legend that the key ingredient in WD-40 is fish oil.[4] However, the WD-40 web site states that it is a petroleum based product.[5][6]