Classic cars forum & vehicle restoration.

[baldeagle]

I was wondering what (preferably cheap) options there are for the underneath of a vehicle when you can see in the future the dreaded rust will get through? I have heard of some spray wax procedure a garage can do, I have also heard of underseal, but would not know where to get it and how to apply it. I also worked on a felt roof recently and considering how hard the black felt paint was to get off my hands was wondering if it would be any good for undersealing a vehicle?

[Rick]

hi baldeagle

The problem with underseal is that it forms a thick surface over existing rust, allowing rust to munch away unseen. Eventually the underseal begins to crack, allowing damp in behind it, speeding up the rusting process even more.

Others will have better advice on specific paint and rust preparations to try, which depend on how rusty (or not) the underside currently is. But if there is any evidence of rust already, I'd personally avoid hiding it away behind underseal. A mantra drummed into me years ago by a welder friend - Rust Never Sleeps!!

Rick
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[baldeagle]

Cheers Rick. How about if the beginnings of rust were sanded and primed, and maybe a rust killer (any recommendations?) first, would some type of underseal be ok then?

[bob2]

If there's just surface rust I'd clean it first, sanding it down with 40 grit and slowly going through till about 320/400 grit, than apply a rust converter and follow the instructions of the rust converter to see how much time is needed for it to dry before paint can be applied, then paint some primer on ( a couple of coats) and a couple of coats of the topcoat you want to give!!
You can use also stone guard (much better than underseal) but you'll have to paint it with a topcoat cause I beleive its porous!!
Or else clean the underside with a jet/power wash and leave to dry then (after the rust areas have been treated and paint applied has dried) apply waxoil into all cavities and paint it on the underside either with a gun or by brush!!

However if its more than just surface rust the best option is to cut it out and replace with sound metal!!

Take a look here for some good products you can use.
http://bilthamber.com/shoppingbasket.php

[ukdave2002]

One of the troubles with rust is that its often not visible because it starts inside a box section due to condensation. I saw a petrol tank fail because of this, the car in question had been left standing with half a tank of petrol for about 3 years, when it was put back on the road the old petrol was drained and just a drop put in to get the car to a petrol station on route to the MOT station, the car was filled up and the promptly deposited half of the petrol back on the garage forecourt, the tank had corroded all the way round at the level to the petrol had stood

In the days before manufactures were offering 10 rust guarantees on new cars, the professional rust proofing firms used to have individual diagrams of cars indicating where box sections should be drilled and what wax injected etc , these may still be around for you motor?

Cheers Dave