Re: Rust undercoating too late for an '05 SUV?
It may be worth your while if not too far gone. Some places that "rust proof" do little good and don't know how to treat. Undercoat as I remember it is a sound deadener and does just that, does not prevent rust. Many will get brittle over time and crack and let water penetrate. At this point you would probably be best served by a more thin penetrant and light coating, something along the lines of cosmoline or a mix of it with a penetrant. If done right it's a messy job - besides spraying the underside you need to get over wheel arches, inside doors and quarters, fenders, trunk lid, seams on panels, all the usual rot areas. Personally I'd get a cheap sprayer from HF and try out/experiment a few things myself, see how it looks a few months later, rather than try the rust converters and painting. Can't do any harm if the rust is already too advanced.