We have cold and hot rolled sheet steel 1/4" thick that we roll/form into 9' diameters. Then we blast clean them using S-280 in a centrifugal turbine wheel room. Blast Cleaning removes 100% of the mil scale. When finished blasting we find microscopic "whiskers" on the surface that appear to be created during blasting. Under magnification they don't appear to be fugitive abrasive particles, rather defects from the steel. These "whiskers" are only found on the outside diameters of the diameter of the rolled weldment. If not sanded off, they will cause a paint defect and subsequent coating failure.

Question 1. Could the "whisker" be created from surface tension of forming the round shape? If so, would pre blasting impart a compressive stress in the surface and the resulting form process be resistant or prevent the "whisker" effect from occurring?
Question 2. Is the abrasive shot size too large and aggravating the surface to form the whisker?