Post some photos of the actual bike in question.

I'm working on one with some quite deep rust. So far it seems like it will be ok, but I still have a bit more work before painting.



The Mercier does seem to have these worm-like tunnels under the paint which as far as I can tell are rust, which is a bit concerning

I've been riding my old Colnago for years, and it has built up some rust, mostly surface rust. It'll get stripped.... soon. But, it has gone thousands of miles with decades of wear and some rust.