truck bed liner-type stuff for inside the car?

[davepoth]

I'm in the middle of restoring a car, and I don't want it to rust away within six months of finishing it. One of the big problems with the car before I took it off the road was that the inside of the floor was rusted, it seems mainly due to water soaking through the carpet, combined with the floor getting bashed about by people and things getting in any out which would have broken the paint and allowed water to get in.

I was thinking that if I found some sort of product to coat the floor of the car and protect against that sort of thing. The closest thing I can think of is truck bed liner, but does anyone have any better ideas?