You don't generally leave your airplane soaking in cleaning solution
for extended periods of time. Try repeating your experiment by using
Simple Green to clean off a greasy scrap piece of bare aluminum sheet
and then rinse it well with a generous amount of clean water, dry it
off and then let it sit for a couple days. You won't find any
evidence of corrosion. Simple Green has a high pH (alkaline, around
9.5 or so), probably contains a small concentration of NaOH or KOH in
solution. Using any alkaline aqueous cleaning solution on aluminum
requires good judgement on how alkaline the solution is and how long
you let it remain in contact with the aluminum. Mildly alkaline
cleaning solutions like Simple Green or 409 are usually OK on dull
aluminum as long as you just use it to cut the grease and don't allow
prolonged contact and rinse off all residue *completely* afterwards.
However, don't use them on polished aluminum unless you're intending
to re-polish the metal afterwards :-)

"Paul" wrote in message ...
"
Simple Green is a NO NO on aluminum planes.


I took a piece of scrap 2404 that was nice and shiny.
I immersed half of it in a simple green solution and left it for
a couple of days. The portion that was immersed exhibited
a decidedly frosty appearance.

This let me know that Simple Green does NOT belong in any faying
surface.

Cheers:

Paul
NC2273H