Dissolve Aluminum from End Mill with Sodium Hydroxide

During a recent experiment, I loaded up a brand new end mill with aluminum on it's very first cut.

Aluminum is very sensitive to Sodium Hydroxide, which is a cheap and easily available chemical. I was unsure whether the carbide, cobalt binder or coating were susceptible to it, but it was worth a test to see if one can dissolve away the aluminum. Before:

I just added a bit of Sodium Hydroxide to water in a small container in no particular proportion.

Very quickly gas evolved.

Within a few minutes a significant amount of aluminum had dissolved already, but then I just left it in the garage for the next couple of days, just spot checking once a day. When spot checking, the reaction had usually stopped, so I had to add more Sodium Hydroxide. But in the end, I got a nice clean endmill out of it. I think if I had loaded up the solution with enough sodium hydroxide, this could have finished in under an hour.