Oxidized Aluminum... More than just dull.

[Sonex1542]

Ok, so made what looks like a big flub. In moving my kids out of the house last week I left ALL the wing skins and my extra fuse skins (have then all, which i dont need) outside and it rained, in the factory particle board sandwich. I know aluminum doesn't rust per se. But this is kinda nasty looking, once again just not a pretty sight, still smooth. I'm not worried what the inside looks like.

They now have an ugly mottling on them. It's only the absolute surface, and can be buffed out. BUT it's on both sides. I am planning on painting it so there will be prep work when I'm done with the entire plane and ready to assemble it.

My question is do I need to buff out the inner surface to its original dull complexion? Or not even worry about it? Should I just spray it with primer? There is no signs of the surface being compromised, but god is it ugly.


Thanks
And sorry about this being so wordy

[DCASonex]

Suspect you have already done this, but with particle board bonded with who knows what that might be bad for aluminum, first thing I would do is remove all parts from the stack and wash off any residue from that wet particle board to prevent any further corrosion. You state that the mottled appearance cleans or buffs out easily so it is probably just surface discoloration and you do not have much to worry about.

David A.

[peter anson]

I don't think you have a problem. Just use a fine Scotchbrite pad to hand-buff it off. The supplier in Melbourne, Airport Metals, coats the aluminium sheets in plastic for surface protection. I had the wing skins water-jet cut, including all the pilot holes, with the plastic coating still on. I didn't think to peel it off until at least 2 or 3 weeks later when I found that water had forced its way under the plastic on many of the holes causing spots of corrosion. I polished it all off with a green scouring pad (OK, a kitchen scourer, which is a bit finer than the brown or red Scotchbrite). It took a couple of nights of hard work, accompanied by a fair bit of cursing my stupidity, but it worked.

Peter Anson
Sonex 894

[SvingenB]

It's most probably just water staining. It does no harm, in fact it will prevent further corrosion, it is a well known corrosion prevention treatment, but then it is done on the whole part evenly and looks nice. It is simply the oxidation layer getting (artificially) thicker.

Without a picture it is hard to tell though, but this is 6061, and it does not corrode (like 2024 for instance) just because it is getting wet.

[Sonex1542]

Thanks guys... I realized that Mothers Aluminum polish works wonders. It is just surface discoloration and Mothers plus some elbow grease made the skins look like new again.

Peter, it's pretty much exactly what you probably experienced. I have all the body and wing skins and the after just got between all of them. The particle board did nothing as far as any chemical reaction with the aluminum like steel would have.

Getting close to assembling the wings. Can see light at the end of the tunnel.