I’ve got a clogged sink, and have been reading the labels on a bunch of different products lately. I’d always assumed that they were a strong acid of sorts, which would dissolve whatever sort of material was built up in the pipes. But I’ve noticed that a lot of these products specify that they’re non-corrosive, so I’m not sure what other sort of mechanism may be at play here.
Thick bleach is actually slimy, though.