Re: corrosion

[peterbo3]

Evening 757,
Killrust may not be the go for alloy. Normal treatment for alloy is sand, etch, fill, prime or spray putty then paint. You might need some specialist advice.
But first up, I would looking for the cause of the corrosion. Electrical leakage, dissimilar metals are two starters in a large field.

[PinHead]

If the body is aluminium then applying rust kill or anything similar will not do anything. Rust is the oxidisation of a ferrous material..aluminium is not ferrous.

[Kerry]

Corrosion in alloy can be a fairly complex issue and there can be many causes from disimilar metals to electrical issues to simply bad preparation in the first place.

Killrust certainly isn't the type of preparation you require.

One thing is to take note of what is attached to this door and what attachments are being used. What might appear like alloy/stainless rivets might have a steel mandrel? then there's different classes of material and the cheapest is generally the nastiest down the track.

Really not a simple solution from your description given as it could be one of many issues.

Cheers, Kerry.

[NQCairns]

Buy some of those half teardrop anodes and bolt directly to the middle of each panel, be sure to scrape all the paint underneath for a good contact.
What!!... it would work wouldnt it? ::)

You could always sand and fill with some liquid metal epoxy then sand and paint again, but you need to address the issues raised above, good luck.nq

[Gorilla_in_Manila]

Hi hookim757,

If I remember correctly, aluminium (and other non ferrous metals like zinc and magnesium) don't corrode becuse they form a thin layer of oxide on the surface which then protects the rest of the metal from continuing to corrode. However, if other non compatable metals are put against them and they get wet, you set up a little battery (anode and cathode) and the electrical process accelerates the oxidation or corrosion of the anode. This is what allows a little zinc block on your outboard to protect the rest of the engine by sacrificing itself (sacrificial anode) but only works if it in the water which allows the electrical circuit to be established.
The other thing you can get with non ferrous metals is a thing commonly called white rust but is essentially just a continuation of the oxidisation process. It often forms on nonferrous metals when they are placed togther in close layers and humid air or water gets in between and is trapped there for long periods of time (as in aluminium sheets lying on top of each other or bundles of galvanised steel laying where the member surfaces are flush against each other). Pull the sheets or members apart and the water evaporates and the process stops.

Anyway, you probably know all that already. (I appologise if I am just rabbiting on and stating the obvious) :-X

So for your alloy panelled defender, I would be checking to see that you don't have a bit of copper wire touching the panel on the inside or a nut or something else that has fallen off say inside a door panel and, along with a bit of humid air or water, is causing the panel to corrode.
The other thing could be that you have got some moisture under the original paint and because it is trapped against the surface of the metal, you are getting the white rust sort of problem. If this is the case, the best thing to do is to sand or strip the existing paint off the affected area and scrub off any white rust that might be there. It shouldn't corrode any more once the bubble of paint is taken off the surface. So if you are in no hurry to paint it, it will be better left bare than it will be leaving it as it is.

Don't think the rust kill is what you want to put on it after that - its for ferrous metals. To stop any recurrence you will need to make sure you use a compatable paint and get it to stick extremely well to the metal so no water or humidity gets back in. You may need an etch primer (essentially an acid that eats the top oxidised layer off the panel and roughens up the surface so the paint can grip it). You then might need a fixer (a solution that neutralises the acid) before slapping on the next layers of paint. OR sanding and washing down may be good enough.

You should talk to a good automotive painter about the painting bit. He should be able to make sure you get a suitable paint and advise on the correct surface preparation and painting system.

Whew. Sorry if that was too much. Just read Kerry's previous post again and he said essentially the same thing in a lot less time. :D

Good luck. Let us know how you go.
Cheers,
Jeff

[rick k]

check that the drain holes in the bottoms of the doors are working