Originally Posted by LV2TNDM

Do not sandblast your frames! Specify BEADblasting. This is far easier on the metal and will insure details remain intact.
If you take the frame to be blasted yourself, handle the bare frame with clean gloves and be sure it's coated the same day. Otherwise (especially if you live in a humid environment) micro rust will begin and you'll have the same problem all over again, just under new powdercoat!
And if you really want to try to halt the rust, treat the insides of the tubes with a coating agent like JP Wiegle, or Tube Prep. Just be sure to do this AFTER powdercoating, trust me!