I got careless and used a lye solution to clean an aluminum moka pot. The end result was that the whole thing was covered in sodium aluminate with some stains standing out from the rest.
Here's what the bottom looks like after a whole lot of scrubbing:
Can I get it any cleaner than that, or is this just the corrosion? Is there, in general, a good way to get the aluminates off with a minimum of effort?