Car underbody rust -Using Jack ramps(getting under) and spraying black spray paint, Need guidance!

Danny_G

Car is a WV 2009, and was purchased from up north, where the car got rusty under neath the body.

The underbody has rust on, not serious but is coated with it.

Been advised to get under it, using jack ramps, getting under it and spray it black using Screwfix spray paint
Here is the spray paint
Hammerite Vehicle Underbody Aerosol Seal Black 600ml
£4.99

I have never done this before but am not afraid to tackle DIY, so here are some questions



a) Any guidance/tips on driving up the jackramps? eg, line them and drive slowly, any things to avoid?
Bricks under the car too perhaps?

b) For those of you who have done this before, how long should I expect this whole job to take, - basically raising the car, driving up the jackramps, getting under and spraying the rust, to make it black (for ONE coat) for now....

how long should I expect this to take, approximately? eg 1 hour?

c) Any other advise and tips? (eg wear goggles, have cardboard on the ground) ?

I have a feeling using a spray can upside down will be a bit of a awkward task :undecided

wgl2014

Before spraying anything like this make sure any loose rust is removed with a wire brush.

Also have a good look for any areas that are more seriously affected and need repairs.

angrycrow

First it depends on the location and extent of rust. Any perforation to cills or floor needs dealing with properly.

I have not used the spray but I have had good results with the brush on version. Make sure it is all dry under there first and use a wire brush to remove any loose rust (wear goggles).

Never work under a raised car without axle stands if jacked or the wheels blocked if on a ramp.

Old style metal ramps can normally be picked up at car boot sales for £10 a pair. You only need to raise one end at a time. Getting up the ramps can be challenging unless you add a strip of wood to the start of the ramp to lower the angle. A rubber mat under the ramp also stops them sliding away. Have an assistant guide you on so you don't overshoot.

Allow a couple of hours for the job.

A cheap old school approach is to paint your used engine oil onto the bottom of the car (not the exhaust) It works but makes a mess of the floor under the car. Mechanics will also hate working on the car afterwards as it gets everywhere when working on the car.

Scrapit

I wouldn't expect 5 quids worth to go very far. Have a look at dimtrol or waxoyl or any of the big brands.

facade

Allow most of a day.


As above, use a wirebrush or old chisel as appropriate, to remove all loose bits of old paint and rust. (wear eye protection)


Keep the cans in the warm house as they spray better warm than cold.


Best plan is to jack the car up, and put the ramps under the wheels, but you can drive up them if you wedge some massive pavers behind the ramp, or put some old carpet through the rungs of the ramp so that the car wheels run on the carpet before reaching the ramp, and stop the ramp escaping.



It is not a pleasant job scraping rust off on your back under a car, get a quote to steam clean the underside and treat with dinitrol from someone who offers the treatment, and compare that with your time and trouble.

droopsnoot

Don't use bricks to support the car, they're not suitable for it.

The key with rust, as others have said, is to remove it first. Painting over it might make things look nice, but it'll still be rusty. You might as well say "don't look under the car" as an alternative, cheaper means of not seeing the rust.

Using a spray can upside down will be more than awkward, it just won't work. Most aerosol paint products suggest that you spray them for a few seconds upside-down when you've finished using them, as this allows propellant (and not paint) to clean out the pick-up tube and nozzle. So you'll have to make sure you can get into a position where you can keep the spray can the correct way up.

Personally I wouldn't spray it, I'd use something suitable, and brush it on after removing the rust. That way you can avoid getting the product all over the bits that needed doing, and anything else close by. Nothing shouts "bodge" to me more than seeing paint on things that shouldn't be painted.

DoaM

is this still a thing? (Hammerite the underbody). I remember many of the chain auto shops (Kwik Fit, Charlie Brown, etc.) used to promote this "service" 25+ years ago. I thought the practice had died out, as it was really akin to putting lipstick on a pig.

m0bov

Are you keeping the car for another 10 years?? Its normally things like electrics/gearboxes that give up long before the bodywork. If its got surface rust, it will need to be fully derusted. Chances are there are rust inside box sections. Is it really worth it?

Retrogamer

Here's my experience from rust removal

Jack up car and removed as much rust as possible with an angle grinder and a cordless drill, both using brass wheels.

Painted over the remaining rust, with a rust specific agent (turns it black)
2 coats of this

Then 2 coats of Ronseal no rust paint.

2 years later, looked underneath and all the rust had returned as bad as it was before.


If you just paint directly over the rust without removing lots and treating it, you'll get couple of months max before it returns.

gmm30

If you ignore the annoying American style, this 14 minute video gives a reasonable view of rustproofing a not-very-rusty VW.
https://www.youtube.com/watch?v=iPsGA0GDveU

Note particularly the intensive cleaning and careful masking of things you don't want to spray. As said above, it's a job that will take most of a day. Wear disposable overalls and a disposable hat - underseal is very nasty stuff to get out of your hair.

Joe_Horner

Consider using a wax spray (Dinitrol is good!) instead of "paint type" underseal.

It has advantages that:

(1) It won't come loose and trap water, leading to worse rust.
(2) Especially round seams, it'll creep into hem instead of sitting over the top - which can create water traps for the future
(3) It self-heals if damaged by stones
(4) It's easy to see when / if it needs reapplication because it's transparent, so any rust forming underneath is visible rather than hidden by a "nice" black coating.
(5) It's a fair bit less messy to apply!