Scum on water surface in aluminum cointainer

[pepsivscoke]

All,

I have performed a leak test for an aluminum enclosure that has a bottom epoxied to the bottom by having it sit on the counter top with city tap water sitting in it for 5 days. No leaks but the water now has a whitish scum sitting on the surface, with a black jagged line creeping along just above the water surface.

I know I have seen this before and think it has something to do with the leaching out of the aluminum some chemical compounds, but I am not sure how to say it. Looking for the right terminology to use to help determine what exactly is happening.

J

Windows XP
Pro x64 Edition
Intel Core Duo CPU
E7600 @ 3.06Hz
3.07GHz, 7.98 GB of RAM

 

[berkshire]

If you have exposed epoxy inside the container, your scum may be unreacted hardener, The hardeners on a great many room temperature cured epoxies are amine compounds which are soluble in water.
B.E.

You are judged not by what you know, but by what you can do.

 

[mcgyvr]

city water.. enough said..
I've see a similar white "scum" on the surface of an clean aquarium when leak tested with city water and left to sit for a few days.. IMO its in the water already or is dust/dirt/skin,etc.. attracted to the water surface.
Try it with distilled and seal the container.

Without a chemical test its just guessing..

 

[Compositepro]

Aluminum corrodes in water creating both white and black residues. Did you really use epoxy or the more usual silcone sealant? Silcone releases acetic acid as it cures which will make the issue worse.