Scraplet

Scraplets are metal-eating robotic creatures alleged to be the deadliest disease known to mechanical lifeforms in the entire galaxy.

Biology
Like the much larger Cybertronian species, a single Scraplet resembles a tiny robot and can convert into a form built entirely for camouflage — usually in the form of nuts or bolts. However, they will purposefully attach themselves to mechanical objects as fast as possible, first sticking to it like an extremely powerful magnet and then melding with it, replicating themselves with incredible speed as they do so. Once embedded, they are extremely difficult, if not entirely impossible, to remove, save for being doused in water, which is considered a rare and deadly chemical to them from where they come from. If left embedded and uncared for, however, they will consume mechanical organisms nat by nat until there is nothing left but flimsy, rusty scrap.