are you trying to remove the dull finish(oxidation ) or does it have a dye on it? My Castwell crome plating manual says something about If it has been sealed with a sealer its the sealer that you will have to remove first before polishing can begin .Anodizing is a process of placing aluminum in and electrolyte and passing a low voltage current through it . This causes the aluminu to oxodizeand looks like a honeycome layer of tubes growing up from the surface these tubes conveniently accept dye into them, similar to steel rusting, with the net result of a very hard protective coating. that coat as I understand is like crome plating your aluminum which can also be dyed and sealed. Castwell sell a Aluminum De-oxidizer concentrate if those other things dont work go to castwellplating.com thay can help you.