poppop,
Ideally, after you sandblast there should be NO rust. Unless you are dealing with a sensitive area, you should blast until you have clean metal. I think if there is a brown or rust colored trace remaining, then you still have the potential for it to "grow" back. After blasting, I usually paint with a 2 part etch primer. This primer supposedly will kill areas of minor "surface" rust. I have stated this in a few posts recently and haven't been lept upon by anyone, so I guess I'll keep saying it.
To answer your question specifically, If you REMOVE rust, it is gone, end of story. If you can't REMOVE it for some reason, you do the best you can, then CONVERT the remaining rust to an inert state. Basically, I think the only way to remove rust 100% is to mechanically excise the area...chop it out. By the time you are done reading this your truck has probably rusted away to nothing.
Stuart.
