WD-40 is the trademark name of a lubricant, penetrating oil and water-displacing spray. It was developed in 1953 by Norm Larsen, founder of the Rocket Chemical Company, in San Diego, California. WD-40, abbreviated from the phrase "Water Displacement, 40th formula," was originally designed to repel water and prevent corrosion, and later was found to have numerous household uses.
Larsen was attempting to create 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. WD-40 is primarily composed of various hydrocarbons.
WD-40 was first used by Convair to protect the outer skin, and more importantly, the paper thin "balloon tanks" of the Atlas missilefrom rust and corrosion. These stainless steel fuel tanks were so thin that, when empty, they had to be kept inflated with nitrogen gas to prevent their collapse.
WD-40 first became commercially available on store shelves in San Diego in 1958.