Flash rust removal?

I use a product called LiquiGuard as a phosphate pre-treatment under my powder coating. It's a great inhibitor and not only seals existing rust, but is pretty good at preventing future rust too.

http://www.liquiguard.com/powderinfo.asp

I'm not sure if it would work, but for $20 a gallon it's cheaper than hauling the block to the machine shop for another hot-tanking.

Best of luck!