Just keeping in mind, anodised aluminium is a hard under the surface finish. It’s not on top of the surface like paint. When you remove it, it leaves the aluminium softer and prone to random oxidisation (aluminium version of rust) that can leave pitts.
Putting it in a pot of boiling water for 20 minutes can go a little way to getting some of the protective layer back after you strip the colour off.
FYI if anyone is interested in the science:
If you think of the surface of aluminium on a microscopic level as a bunch of straws with their ends facing up.
Anodising has three stages.
- You remove the very top layer of the straws so they are all open. This is done through a chemical / electrolysis process.
- You soak the item in an organic dye, which makes its way into the straws.
- you boil the item in hot water which causes the ends of the straws to close over trapping the dye inside.
Because we are talking nano scale here, you can still “see” through the top of the straws to see the colour.
This process is a sort of controlled oxidisation, which leaves the surface with a uniform oxidised layer. This layer prevents further oxidisation.
Here are some photos of anodising at home part of a heatsink off an led light to use as part of a science fiction looking grenade.
I used blue food dye for this.
The bit on the top is another heatsink anodised black.