Surface rust on underbody

[YOYO]

Hey all,

I have some rust spots under the car. According to a vehicle inspection earlier in the year it wasn't a major problem, but one that should be looked into.

What's the best way to treat them? I'm thinking of sanding back the spots then spraying a few coats of paint on the underside. Are there any other methods/products to use which are recommended?

[siksII]

u can get that black tar stuff that the underbody is covered with from new to cover the rust up with.. that way it will sort of blend in with the rest of it..

ive seen compliance places doing it as lots of imports have a bit of corrosion underneath (snow in japan doesnt help)

[Jay95R33]

So does this black tar stuff actually stop and kill the rust, or does it just cover it so you can't see it...... Until your floor pan falls out ?

J

[zakalwe]

Hi,

Here's where my years of experience as a VL owner are useful - RUST!

First knock off any loose bits of rust, flaking paint or lifting underseal. Use a wire brush or a bit of sandpaper.

Second, use some rust converter (from the hardware shop) that stops the rust spreading. Let it dry, maybe overnight.

Third, a coat of underseal over the area to keep it sealed up.

cheers

Z

[predator]

also.. etch primer can also be used, which helps prevent corrosion and is used as a base coat. ... its grey also, so shouldn't stand out too much.

[YOYO]

Thanks for the replies fellas. Looks like I'll be sandpapering the ol' girl for a while.

zakalwe, do you know exactly what the rust converter does? Sounds like a sacrificial anode.

[Cubes]

Make sure you kill the sand it then kill any left over rust.

Then hit it with the underbody sound deadner that can be had from any auto shop.

Paint it on. It protects against stone chips and helps with sound deadening.

Providing you have all the rust cleaned up it won't rust under the underbody deadner.

[browny]

This is a good overview of how rust converters work -> http://www.corrosion-doctors.org/MetalCoat...t-converter.htm

I've found the K+H stuff from most auto stores is quite good (tannic acid based).

The best method i've found is to remove as much rust as possible using mechanical means. I like to use a wire wheel on an angle grinder, or you can hand sand but this takes longer. I'm not a big fan of sanding/flap wheels on grinders because they take metal off too easily. Then hit with the rust converter, then paint.

[Cubes]

I wouldn't paint an underbody though.

Paint chips too easily.

[browny]

My comments above are generic for trearting any rust. So by "paint" I really mean "surface coating", which you would obviously match to the area you are repairing.

[YOYO]

Cheers. browny. That makes a bit more sense now.