You are right on the button!!! "Correctomundo - PERIOD!!!"

First of all, as soon as they hit it with steel shot, there's going to be contamination via impregnation, and even if most of the surface oxide layer (Not Glaze) is removed and the aluminum underneath is exposed to the atmosphere, corrosion will begin... The only difference is that the oxidized layer formed on the surface will not be as thick as before unless it's permitted to be exposed to a longer period of time.

You can use this to remove the surface oxide layer:

http://www.orisonmarketing.com/corrosion/aluminator/aluminator.html

Here's the MSDS:

http://www.orisonmarketing.com/msds/MSDS%20Aluminator.pdf

Or this:

http://www.airproducts.com/NR/rdonlyres/D9EB46F4-8C31-487F-B08E-DF8611D49DC1/0/bps_100.pdf

If you still would prefer to blast, then just use a different media like glass beads or whatever this company out of Cleveland would suggest:

http://www.ntruddock.com/abrasives-media.html

Sorry I can't give you more leads but, my pasta has been boiling and the one thing I can't stand is some soft pasta... I always prefer "Al Dente" instead!!! ;) ;) ;)

Respectfully,
Henry