Asked by: Christopher Watts, Liverpool
Corrosive' is a relative term. Hydrofluoric acid, for example, is very corrosive towards glass, but it will not attack the plastic bottles in which it is kept. Fluorine gas attacks just about everything, but it can still be kept in copper vessels, because in attacking the copper it produces a layer of copper fluoride that blocks further attack.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.