Don't worry, it was just a cheap Ultrafire and an aluminium part from my bicycle.
well, it worked. The anodizing on the Ultrafire was type II, I'm pretty sure now, but it was unusually matte. No idea about the bicycle part, as I've never knowingly seen type I so I probably won't be able to distinguish them.
Somehow I felt the urge to throw another flashlight into the pot (one of those cheap 12-LED-3xAAA-things with the glossy anodizing) just to see how it behaves.
Eventually it came off too, but it took much longer, because of the less porous surface, I assume.
The final result was worse than the first one, mainly because I forgot the pot on my kitchen stove once. All the water had evaporated, and everything inside was no more than a brown mess.
Even this mild, not very caustic sulution (it's not much nastier than soap) did its job quite well. Even more than that, it etched away a thin layer of aluminium, so I have to reinforce the threads now.....although I have to admit that I threw in the part a few times in order to restore the finish after messing around with the surface. It stayed in there for about an hour, I guess.
When it comes right out the solution, the finish is pretty nice. It's a very matte shade of metallic white. Must be an oxide layer, but it's definitely much thicker than the oxide layer that forms when you cut or polish the surface. Moisture, from the hands for example, doesn't do anything, leaves no marks ot traces, nothing. It can't withstand much mechanical wear, though.
As soon as I find a HA part, I'll repeat this nice little experiment and keep you updated.
Or maybe my HDS.....?!? I mean, who needs anodizing?
