Originally Posted by BigMo
Use the soda blasting, it doesnt remove metal, just dirt or particulate on the surface.....it doesnt have enough *** to harm the substrate. Sandblasting, bad idea, you will have the aluminum all messed up. Aluminum is soft, and the sand is harder normally, so the aggressive sand will take some of the metal away also.....
I sand blast aluminum intakes all the time, it leaves a "matte like" surface but really doesn't remove any material. On a rough cast surface you can't tell a difference- on a polished one it may be more pronounced, I haven't blasted a polished piece though, always blast first then polish it.