I typically use a glass bead cabinet to clean parts prior to welding, followed by a wire brush adn sometimes acetone wipe. Back into the bead blast cabinet after welding if appropriate. That is not to say a soda blaster may not work, unless there is a problem with contamination when using soda?

I have only seen soda blasting used for thin sheetmetal such as with automotive bodywork, mostly to prep a restoration project and identify where the rusted areas are. using anything too abrasive or too large on the sheetmal body panels will warp it due to the impingement of the media onto the sheetmetal, as well as the heat generated by the friction of the media.

John