Cleaned the car today and noticed severe deterioration in the rust under the wheelarch. I spotted this bubbling before winter, but I guess the salt on the roads has made it worse, now the paint has come off.

I’m keen to treat this before it gets worse.

What is the best method to stop it spreading and prep it for touch up?

From the picture that doesn’t look too bad. If it’s still good metal clean it up with a wire wheel on a drill. If it’s a bit to fragile for that wire wool or sand paper. Then treat it with Vactan, it’s very good, cheap and goes a long way. It’s about the best rust treatment around.

I’ve found it’s best to put it on with a sponge brush because it gives a flatter and smoother finish. Don’t sand it down, then put on a high build primer which you sand to a flat finish and finally your top coat.

My mates had the rear arches on his 3 series done twice now. Done by decent body shops both times. Both said the same things, to repair properly you need to blast the area clean or cut-out & replace but he went with rubbing down & filling (the cheaper option).
From faffing around with mk 2 & 3 Escorts in the 80’s, you need to get waxoil/old engine oil inside the arch where the inner & outer arches join. FWIW I think those arches are beyond repair mate. I’d be inclined to Jenolite it & hammerite them.

Bilt Hamber is good stuff, I’ve used it on my Mazda and it works a treat.
All you’ll be doing is delaying the inevitable though, as takisawa2 said above, its pretty much terminal rust that. A rubby down and treat/skim/touch up will do you a year at most.

Thanks all, car is fine otherwise so I don’t mind treating it regularly if need be. I’ll have a look at Vactan, cheers.

I’d take it down the local bodyshop and get them to sort it.

I’ve just spent a small fortune on it, so I’m reluctant to spend any more…

bit late to ‘treat before it gets worse’

longer term need to let some new metal in. You can get repair panels for most cars.

short term just need to keep tidy and neat and no sharp edges for MOT etc

Bilt Hamber Deox is the best stuff ever, rather than convert the rust it dissolves it, the possible downside being it might not leave you with much good metal, depends how bad it is, amazing stuff though.

That looks like it will be pretty lacey once the rust is gone. Having done up some old machines in my time, the best way is to use a spot sand blast gun if there’s any pitting at all. Follow that up with etch primer.

Deox is ok, but it never really gets into pitted areas properly. If you get rid of all the rust and recoat it, it’ll be halted until the paint’s broken.

What is it by the way? Ford or something Japanese?

shot blast it with a small recirculating shot blast gun, etch prime then hammerite it till you can get it painted properly

I think the photo makes it look a little worse than it actually is. It doesn’t feel particularly fragile. I’m just suprised at how quickly it deteriorated.

The car is a 2003 Audi A4. *hangs head in shame*

If it’s an Audi, then I expect the arch on the other side of the car still looks perfect, and that panel has had some work done on it in the past.

Spot blast it, both sides. Just get a cheap blast gun from lidl, aldi or Ebay. Feather in the good paint with sandpaper if you need to paint beyond the arch lip. Rattle can etch primer. I’d probably give it a skim of filler or stopper in any pits, rub it down and then prime it with normal primer. White rattle can, then polish up after it’s had a bit of time to harden. You can get away with a lot on a white car.

Inside the arch, you can just etch, topcoat and stone chip.

If it’s an Audi, then I expect the arch on the other side of the car still looks perfect, and that panel has had some work done on it in the past.

Spot blast it, both sides. Just get a cheap blast gun from lidl, aldi or Ebay. Feather in the good paint with sandpaper if you need to paint beyond the arch lip. Rattle can etch primer. I’d probably give it a skim of filler or stopper in any pits, rub it down and then prime it with normal primer. White rattle can, then polish up after it’s had a bit of time to harden. You can get away with a lot on a white car.

Inside the arch, you can just etch, topcoat and stone chip.

Thanks for that, the other arch is ok. It does look like there might have been some minor damage at some point. The car is actually light blue, but my phone camera is crap.

A 2003 A4? I’m shocked to see that on a VAG/that age. Could it have been a poor damage repair previously?

Do a google search for “Por 15” I used it to treat some rust on an old banger some years ago and it appeared to last really well. Nothing’s as good as cutting out and welding in new metal though.

From the picture that doesn’t look too bad. If it’s still good metal clean it up with a wire wheel on a drill.

Sorry, but if it’s got to that stage its not coming back easily.

It was only 12 months after that (and after I’d ground back, treated, sprayed and sealed, that my whole arch fell apart. I’ve spent literally hours repairing, spraying and baking the various parts. I’ve even welded in a new rear arch, and it comes back again the next winter. Once rust starts you have to keep on top of it every year. It might be worth your while, it might not – your call.

Rusty wing fix by j.buckle, on Flickr

Stop worrying about it – the car isn’t about to fall apart.

Pour yourself a nice cuppa and put your feet up.

globalti – Member
Stop worrying about it – the car isn’t about to fall apart.

Pour yourself a nice cuppa and put your feet up.

I’d either go with this advice, or get it done properly (new metal).