Hi  Archie
The bake and blast system seems to be the very best way to get rid of rust on cores.
There is a smaller but time consuming small vat size of material but it takes a week to deep clean a large block.
It uses a feed molasses  in hot water which creates a reverse electrolysis situation to remove rust.
It uses a small current from the liquid to the block and it works really well.
But bake and blast or even just a hot tank clean and a tumble blast type clean is what I have gone to for rust on cores or customers components to avoid the long time spent in the glass bead cabinet cleaning rusty parts.
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But yeah there is no chemical that removes rust especially in the cooling system passages.