Only for steel. You can't sandblast an aluminum frame. It literally removes the soft metal. You use walnut shells, or actually soda blast media. Most powder coaters have ZERO knowledge or education regarding thin wall aluminum bicycle frames. They are used to heavy alloy stock from automotive applications. They'll literally blast a hold through the side of a Klein, Mogul-Bismark, or a Cannondale if you give it to them. They don't "love" bikes and time is money to them. They use a coarse media because its faster.

Never ever ever sandblast alloy bike parts. Steel, sure.