Aluminum corroded aluminum

[cole3444]

I have read thru numerous threads and post and am needing a little extra support on aluminum corrosion on the roof. I have read where Airstreamers have patched roof areas with new aluminum and was wondering if the corroded aluminum needs to be cut out to avoid future corrosion. Found an area 1' X 1' and two spots the size of a quarter that punched thru while stripping the roof. This is in the area where 30 or more sheet metal screws were in the roof near the A/C opening. Need some advise. I appreciate all the other info I have received during my off frame resto

[J. Morgan]

I don't think aluminum corrosion "spreads" like it does on steel, I don't think it is necessary to remove the corroded aluminum if you were to patch over.

[J. Morgan]

Although you might anyway...

I didn't think they would oxidize that much on the roof.

[cole3444]

Thanks for the response, My other question to anyone that has replaced aluminum on the roof does the rivets need to be removed on the old and then rivet the new sheet to the supports through the old. would it give anymore support? Was their a reason all the sheet metal screws were installed near the A/C opening about a 2' X 3' rectangular shape not sure from factory or PO.

[KeithC]

I have never seen or heard of the corrosion you wrote about. But, there is metal chemical reaction between different metals that are contact. I'm thinking aluminum and non-aluminum/stainless steel screws. If non-aluminum screws are inserted very closely, could the reaction erode/corroid the patch?

[Aviator]

My 1970 had 59 steel screws holding the old Armstrong AC on. 3X2 sounds about right for the footprint. I covered the entire area with a new sheet of 2024 T3 alclad, sealed around the edges, and buck riveted it on.

[Aerowood]

Aluminum corrosion will spread. Your best bet is to removed the corroded areas.

[cole3444]

Thanks Aviator and Aerowood, hoped you would give input on this issue. Will cut out the bad place and put a new sheet that covers the screw holes and the bad spot. Will Tempro along the edges and rivet around the edges and where the supports run to take care of any leaks. Do you all think the current rivets will cause any issues. Enjoy reading your forums they have helped greatly.

[Aerowood]

Remove any structural rivets that will fall under the patch and incorporate them into the patch. Do not put the patch over any unremoved rivets or fasteners.