Oxalic acid can and is used by many people to clean up rusty/ugly painted bike parts without worrying about damaging the pant or even decals. It's a really good way to clean up an ugly bike that has been left out to get rusty but the surface rust hasn't spread out to bubble and destroy the paint with more serious body cancer below the surface. For surface rust and rust stains on paint it's like magic.

I would think a senior member of this community would "know" this.