I see occasional multiple spoke failures on almost unused bikes, with spokes broken at random locations along their lengths. These wheels always have many small inconspicuous dark specks of corrosion that can be felt in the surface of the spokes. Almost always, the failures occur in both wheels.

Typically, the customer reports that the bike was fine when they last used it, but has suddenly broken spokes without having been ridden.

In diagnosing the problem behind these multiple spoke breakages, I find that the common factor is chlorine-containing chemicals like bleaches or pool chemicals stored in proximity to the bike.

Corrosion from exposure to chlorine and its compounds is a known shortcoming of stainless steel. As you move up the cost ladder of stainless alloys that have superficially similar physical properties, e.g. 304 - 316 - 321, oftentimes the only major practical difference is resistance to chlorine compounds.