I’m glad I saw this thread. After buying a few setups to get started I ended up with three kettles, two ss and a short wide aluminum for frying fish. The aluminum one had never been. Not a good size for brewing, but I have made some super simple LEM kits where you only boil 2 or 3 gallons of water, add the boiling water and LEM to your fermenter then top off to 6 gallons.
All I’ve done is boil either distilled water or filtered water and it has started developing a white film at the level of the water along with what I would describe as scorch marks.
I just put the last batch I made in the keg and force carbed it out of the last gallon I bottle three 12oz bottles (I probably could have bottled a fourth... but don’t want to be greedy.) and added a carbonation tab to each bottle.
The beer in the keg is slightly off, can’t quite put my finger on it, but still drinkable. I opened one of the three bottles after two weeks because while capping it I discovered it was a twist top. Over carbed for a stout, but didn’t notice any obvious off flavor. The other two, about a month and a half later way over carbed and undrinkable. Everything was washed in PBW, rinsed very well and sanitized.
I was thinking maybe it’s the aluminum kettle. If anyone wants, when I get back in town tomorrow I’ll post a picture of it.