Use household ammonia damage aluminum? I'm sorry if this has already been asked but I could not find it on a search here though I also could not determine how to search for the presence of two words ('ammonia' and 'aluminum')

I've read mixed results about whether using household ammonia on aluminum is damaging or not. In my case I want to use it to clean baking trays by putting some (~ 1 tablespoon to 1/4 cup) ammonia on the pan and cover it with a plastic bag and set it aside for hours or a day or so to allow it to soften the baked on grime. I also want to and am using it for a variety of other household and tinkering projects. I read on one site that it is a very bad idea to use ammonia on an aluminum bike frame because it will severally weaken it.

Does household ammonia damage aluminum?
Yes, aqueous ammonia is likely damaging in time to metal Aluminum in the presence of air and any salts (from outside dust,...) that may further serve as an electrolyte. 

Ammonium salts, themselves are good in transporting solvated electrons, and here you are, unintentionally, likely creating a metal-air battery scenario. 

Possible half-cell reactions:

$\ce{ Al -&gt; Al(3+) + 3 e- }$

$\ce{ O2 + 2 H2O + 4 e- -&gt; 4 OH- }$ 

Resulting in a net cell reaction of:

$\ce{ Al(3+) + 3 OH- -&gt; Al(OH)3 }$

The aqueous ammonia may also assist here in the removal of the Aluminum hydroxide by forming a "dissolved/peptised/supersaturated hydrated alumina" (per a paper 'The Precipitation of Aluminium Hydrous Oxide and Its Solubility in Ammonia' by Prideaux and Henness).

In essence, Aluminum is now a more rapidly corroding anode. 

Nice experiment, albeit, unintended.