Use the stinky kind of Easy Off, not the no smell one. The time it takes depends. You need to keep an eye on the part. I'd look every couple minutes. Once the color is gone take it out and wash with water. The part will look dark. You need to polish it out. You might need to wet sand with 400 then 600 then 1000 grit sand paper and finally some aluminum polish like Mother's mag polish.
If you leave the part in too long it'll eat away the aluminum!
Do it in a well ventilated (outside) area!
Have fun.
