I have never had to play with aluminum drums, but cast iron will always come off with a good soaking of penetrant on the center (PB Blaster comes to mind) and hitting the drum at a 45 deg. angle at 9:00 (3:00 if a righty) far harder than you think you should with a 2 lb. sledge. Works on my Z, '69 Cutlass, Monza, etc.
A shop teacher at Sierra (Sacramento anyone?) showed me years back. Low tech still has a place in the world.