We are in the process of Die Casting some of our Aluminum parts but having a hard time Hard Anodizing the die cast parts and am not sure what grade alloy they are using

I was wondering if you could give me some pointers and possibly a process and grade of alloy we can get the best result on esthetically? As well I believe the silicone in the alloy is giving us the porous and dull finish so is there any recommendations on how to improve that?