Home Forums General Discussion Shot Peening Process, Intensity, Coverage nice finish on aluminium castings

I'll give it a try, you may need to provide more information.
If all you are doing is prepping the surface for clear coat or other organic coating, 25-50 psi with 180-220 grit aluminum oxide should be enough depending on your paint system and preblast surface finish. As cast surfaces may require 80 grit at 40-60 psi to meet the finish you want.
Different paint systems may require different surface preps.