Alan,
Eastwoods and other companies sell soda blasters for metal preparation prior to painting.
The media is not cheap but there seems to be many benefits to using this type of media. Some people think it shoots soda ash - it shoots sodium bicarbonate (specially formulated granules of baking soda). It is human-safe, environment-safe, and mechanical equipment safe.
Maybe someone who has personally used a soda blast system will respond.
Tim
