Oxidsiing aluminium

[Lankstarr]

Someone recently told me that the aluminium on their car had oxidised and ruined the paint work - so they resprayed the car.

Surely aluminium can't oxidise unless exposed to oxygen (ie not under 387 layers of paint) and this guy was telling me porkies:confused:

[simonprelude]

It amazing what happens when a car receives a stone chip, or door ding, then is repaired.

The Aluminium will have been subjected to the air, then covered, this does not stop the process.

[WhyOne?]

It amazing what happens when a car receives a stone chip, or door ding, then is repaired.

The Aluminium will have been subjected to the air, then covered, this does not stop the process.

Oooo-errr!

So how should one treat aluminium if the paint is chipped/scratched deeply enough to expose the metal?

[Lankstarr]

maybe one has prematurely judged then! something would have had to happen to the paint then - understandable to see a bonnet that has been resprayed but a whole car (bar bootlid and roof)!?

The rear bumper wqas done and that wouldn't oxidise.. and if the whole car was done for completeness and matching then why not do the boot lid ?

[Steveycaz]

[quote=Surely aluminium can't oxidise unless exposed to oxygen (ie not under 387 layers of paint) [/quote]

...23 layers of paint, surely:confused:

[simonprelude]

If a panel has 100% not been damaged at all, not even a pore in the paintwork anywhere, then I would suggest some form of contaminant was present before the paint was applied.

But without getting my engineering text books out, that is as far as I could go :( Sorry !!

:)

[Lankstarr]

...23 layers of paint, surely:confused:

don't believe everything you read Steve, a slight exageration on my behalf:)

[Paul]

don't believe everything you read Steve, a slight exageration on my behalf:) ... although in Luke's case I think he might be nearer to 387 layers than anyone else on here ... ;-)

[TheQuietOne]

I would have thought 69 was closer on Luke's...;)

Oh by the way it is the Type-R in Scotland we are talking about I assume mate?

[Nick Graves]

Isn't one supposed to acid-etch aluminium, before painting?

Otherwise the paint won't stick to the Al O3 layer.

I cannot remember the exact product required: Good ol' webnet!

Etch primer
Aluminium forms an oxide layer when it is exposed to the atmosphere. It is this layer that stops it corroding further but this layer also prevents paint from sticking to it well. To make the final coats adhere to the aluminium, it is necessary to use an etch primer which will "key" into the aluminium surface after the surface has been prepared by sanding. I used one in a spray can as the quantity required is not that great. Only a thin coat is required.