Corrosive is a product of water chemistry not temperature. Precipitation of minerals is another.
At my elevation, I think boiling water is only about 200'F or less.
In any case, there is no argument that the flow thru beasts get limed up - you can see the rigs designed to acid wash them, and read the MFG's instructions. With an electric rig, you can go decades between a bottom of tank vacuum job.