Fluoroantimonic acid is the strongest acid in the world; it can rip through most materials easily. But a chemical that you've got around your house will stop it cold.
An acid, when it hits water, produces positive hydrogen ions looking for electrons. Certain materials will lend electrons more readily than others. Metals will often hand over their electrons, corroding themselves to do so. Cellulose from plants, or the proteins and fats in a human body will also donate electrons. Glass is not so keen on donating electrons, which is why most acids are kept in glass containers.
Fluoroantimonic acid doesn't give glass a choice about donating its electrons. One antimony atom, surrounded by a star-like cluster of fluorine atoms, its single hydrogen atom is ferocious in liquid. That hydrogen atom will tear glass apart. It will tear anything apart.
Well, except one thing. It's simple stuff. It surrounds two carbon atoms with four fluorine atoms. This uncomplicated configuration can be linked in a long chain, although it's a difficult chain to work with. The carbon and the fluorine bond together in one of the strongest bonds known to chemistry. They aren't giving any electrons up. It took scientists a long time to get this substance — polytetrafluoroethy — to stick to anything other than itself. When they finally managed it, they marketed it as teflon.
Yep, the same substance that keeps your food from sticking to teflon when it coats the surface of a pan also keeps the world's strongest acid at bay. Teflon can be a thin coating, but it's too tough to breach. So until fluoroantimonic acid gets itself a metal spatula, we're all safe.