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MG MGA - Aluminum Oxidization

I'm hoping you can help me out with this!

I just sucessfully pealed back the door skins in my MGA (which are in quite good condition) and noticed that there was a lot of white powder in the cracks and on both the aluminum and steel sides. There was also some pitting on the aluminum side as well. I'm assuming that this is oxidization and it came off fairly easily with some sandpaper.

How do I treat the aluminum so that it stops oxidizing? It is like rust such that you have to get it all out or else it will come back? Are there any chemicals that are used to stop the oxidization process?

Thanks, John.
g gillian

Hi John, The oxidizing your seeing is caused by the dissimilar metals coming into contact with each other. I'm actually surprised these mga doors have lasted this long. Steal and aluminum react badly with each other, specially when moisture is added.
The best we can do is to put a barrier of paint between the two metals. I removed the skins from my doors, bonnet and boot as well. I media blasted the frames and gave them a couple of coats of "Chassis Saver" paint (epoxy paint). I cleaned the insides of the skins using a sos pad and primed them with self etching primer. Add a couple of top coats and we should be good
I'm hoping this will solve the problem.

-Cheers
Bruce

B Suelzle

The MGA door skins are 5052 material, which is a marine alloy with outstanding corrosion resistance. I think this is why there are not more problems with corrosion between the skins and the steel frames. Best thing to do is coat each piece with epoxy primer, and if you can, assemble with a wet coat of primer in between. This is messy, but it is pretty much the best you can do. If you really want to go the extra mile, you can treat the aluminum skin with the Alodine process before priming, but then you are dealing with some fairly toxic chemicals that you'll have to dispose of afterward.
Del Rawlins

I have a spare boot lid that I intend fiiting to the car as it has holes in it for a boot rack. (I cant bring myself to drill holes in the perfect boot lid already fitted ) The spare lid seems to fit fairly well but has been left too long in the stripped state an some pitting has appeared mostly on the interior surface of the alluminium. The frame hss some light rust too.
Would a coating of epoxy primer solve this or would I have to have the alloy sandblasted to polish this off before any paint was applied.

I know new ally panels are available to fit to the doors, bonnet (hood) and boot but I was hoping not to have to renew the ally if possible,

Thanks
Colyn
Colyn Firth

I wouldn't try sandblasting anywhere near the aluminum skin, too soft. I'm planning to remove the skins from my doors so I can sandblast and prime the steel frames, but I also have some extra doors that are in pretty horrible condition that I am going to use as practice pieces first. For cleaning corrosion off the skins, I wouldn't try anything more mechanically aggressive than hand sanding, or maybe some acid etch to get into the pits.

http://www.aircraftspruce.com/catalog/cspages/alumiprep.php
Del Rawlins

There is a Chemical called "Alumiprep" you should be able to get it from a Automotive paint supply. Use that and scrub it with a fine stainless steel brush about the size of a toothbrush that should take care of your corrosion in the pits, if you can't find that there is a chemical made by Duro similar to "Naval Jelly" but for aluminum that works quite well. I would second not media blasting it it will distort the panel badly.
John Nelson
J E NELSON

This thread was discussed on 05/02/2010

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