Convair needed rocket rust prevention — 39 formulas failed, then WD-40 worked everywhere

In 1953, Convair — a division of General Dynamics — was building the Atlas missile, America's first intercontinental ballistic missile. The missile's thin stainless steel skin was vulnerable to rust during storage. Convair contracted San Diego's Rocket Chemical Company to develop a water-displacing formula that would protect the metal. Company president Norm Larsen set to work.

Larsen mixed and tested formula after formula. His goal was a substance that would drive moisture away from metal surfaces and leave a protective barrier. Each attempt failed the Atlas missile test. After the 39th failure, he tried again. Formula #40 — standing for Water Displacement, 40th attempt — still did not meet Convair's requirements. The Atlas missile ended up protected by a different coating entirely.

The Rocket Chemical Company had spent years developing a product for one customer with one use case, and that customer did not want it. But Larsen noticed the formula worked brilliantly on everything else: it freed stuck bolts, silenced squeaky hinges, prevented rust on garden tools, and displaced water from ignition systems. He began filling aerosol cans by hand and selling them from the trunk of his car.

By 1958, WD-40 was available in San Diego hardware stores. Within a decade it was in airline maintenance manuals, on farms, and in military depots. In 1969 the company renamed itself after its product. The formula has never been patented — kept as a trade secret instead. By the 1990s, WD-40 was in four out of five American households. It was inducted into the International Air & Space Hall of Fame in 2014 — not as a rocket part, but as a rust-preventer that failed at exactly that.