Hot tank

My understanding is that few outfits use "hot tanks" anymore, having gone somewhat greener. Is it possible you asked using the wrong terminology?

Lol, yes! I rember the machine shop used to use a method that I recall being called hot tank or boiling, or? They would use this method to totally clean a bare block down to raw iron, IIRC.

So likely my terminology is outdated, there must be somewhat of a greener method(?) any ideas?