Not all grades of stainless are rust proof, most in the 300 series are but I'm not sure what grade Glock barrels are made from. Scratching would appear immediately though.
Yeah, whatever "stainless" kimbers and Taurus use sure do rust easy.
But my point was, if you have a raw stainless barrel like pictured in the OP bead blasting it isn't gonna cause rust or any other issues.