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ALLI CORROSION


CHRIS GALE

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Does anyone have this problem on their seven?

My car is two years old and I have noticed a small bubble the size of a one pence piece on the lower part of the side skin under the paint. I can only think that this is alli corrosion and I am unsure what to do. Any suggestions?

 

C7 CJG

 

 

 

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I would suspect that if it is right at the bottom where the skin touches the chassis, then it is more likely chassis rather than ali that is corroding

 

size of a 1 pence piece, so similar to a greasy finger print left on the bare chassis before it was powder coated

 

sorry not sure what you could do

 

rob

 

Edited by - robmar on 22 Jan 2002 09:49:00

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It will be chassis rust causing it.

 

I've yet to find a solution as I have a bit on mine too (left hand side at a triangulation of the chassis tubes). So far I've just blasted as much of the crud out with soapy, then clean water. Made sure it's thoroughly dry and then used rust proofer on the chassis rail where I can get access.

 

I think the only way to cure it properly is to pull the side skin away from the chassis, sort the chassis rail out then "refit". However I'm 99.9% positive you'll muller the side skin doing this and it'll look like a dog's dinner afterwards.

 

I did have someone give me an estimate of 150-200GBP to sort it once. Wasn't that bothered (as the tube is perfectly fine and the blisters don't bother me that much).

 

I've now decided to keep an eye on it and in a few years' time I'll probably strip the whole car down to the chassis and send it to Arch for a thorough overhaul.

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i had exactly the same problem on my 3yr old k seires. It is indeed alli corrosion due to salt and grime build up in in the small gap running inside and along the footwell area. The bad news was re skin was required, although the chassis was absolutely fine except for a clean and a bit of protection applied. I'm now paranoid about salt and dont venture out when the gritters about. I have also sprayed waxoil in the void and used duck tape to tape up the access to this area's from in front of the footwell (you would be amazed how much crap has gathered on the tape which would have otherwise entered the void).
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Lots ofcorrosion on my 1995 car with 50K miles on the clock, you don't need salt, but removing the aluminium pannels as the electrical earth may help!

 

Bi-matalic corrosion between the two dissimilar metals is enevitable. Isolating the two by a layer of silicon sealent will help. But as the floor pannel is strustural you want to have a good tight joint between the chassis and the ali...catch 22.

 

Simon

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Ages old problem. Check-out Landrover (class action lawsuit in USA) and aircraft.

There are neutralising chemicals for the aluminium (aircraft industry could help here).

From my experience, powder coating is crap. Just one small chip or crack (unseen) and the water creeps (capillery action).

No cure!!!

Slow it down by scraping bac to clean metal, painting with anti corrosion, then paint then waxoil. Good until it comes through again!

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Yes this topic has been covered before, search under rust and corrosion. Lots of comments on ally skin corrosion and on the questionable powder coating that Caterham use. From memory there were certain years of car that seemed to suffer from both powder coating issues and corrosion of the ally skins. My car is a 1990 build and so far the ally skin is ok including the dodgy areas around the sill where the bulk head is. I've had lots of issues with powder coating including two wing stays that lasted only 12 months. Having stated that I had my roll bar re coated in July of 2001 by a local outfit and the coating is now rippled on the curve of the bar and the dreaded rust is coming through. Out with the matt hammerite me thinks.
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Don't know how the ali is fixed to your cars in that area but if you could drill out the local rivets (they would have to be local to the rust problem) and again (if) you could buy or make a washer out of magnesium then you could attach this to the rivet. This would give you a metal 'washer' that would prefer to corrode more than the alumninium does. You'd eventually get a loose rivet but it would take some time. It's really essential to keep that area clear of mud on later cars as damp will collect and you eventually end up with acidic mud (believe it or not) which clearly will not do your paint / corrosion problem any good whatsoever.

 

Ps Hello Mike.

 

Nigel Mills - 2.0 Zetec carbs

 

Edited by - millsn on 23 Jan 2002 18:45:38

 

Edited by - millsn on 23 Jan 2002 18:46:43

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