What happened to our aluminum pans?

Factual Questions
1

We have a small collection of frogs and toads which we keep in glass terrariums. We also, occasionally, have invasions of ants which really seem to like to get into the terrariums, probably looking for dead crickets and such. Because the ants are a real threat to our critters, we keep the cages set on plastic pedastals which are in turn set in a shallow moat of water contained in aluminum pans. The pans are the type of disposable shallow cake pans you can get in the baking section any grocery store. From time to time we refill the moats with tap water.

Yesterday, two of the aluminum pans started leaking. When we looked them over, it appeared that they were both corroded through somehow. What kind of reaction is going on here. And should we stop drinking our tap water?

2

Do ants ever get in the moats and decompose? Aluminum pans are very reactive to acid. Ants contain acid (formic acid to be specific).

3

Not these pans. These were relatively new (about 2 months old), and we haven’t had any ants lately.

4

there are hundreds of types of aluminum alloys.

most aluminum objects form an oxide rapidly, wire brush the metal to shiny metal and you can just about watch it get the usual duller finish, this oxide actually protects the metal if the metal keeps mostly dry.

with abrasion and/or being in constant water the metal can continue to oxidize until it starts to disappear.