From the technical point of view I think that you ought to find someone to phosphate it BEFORE you bead blast it as it starts to corrode (that's rust.....) the moment that the clean white steel leaves the bead blasting cabinet. And make sure that you fill the blind holes with a bit of tight fitting wood and replace the screw into EVERY threaded screw hole too.

A lot of steel fabricating manufacturers have phosphating plants - or they used to!