Heating up EN Baths

I have not used one, but several companies sell a small external heater that uses extremely turbulent flow to retard the plate out that you would normally get from using steam heat temperatures. I was impressed by the claims and from a person that had one. Hot water is too slow. You will have bath degradation. The optimum way to operate EN is to have it get to temp rapidly and then get product in it immediately with no down times for lunch. Adding your make up water after heat termination at the end of the day allows the temp to get out of the autocatalytic zone faster. Cooling water thru your steam heater really helps also.

For coils, I personally prefer titanium for greater corrosion resistance and they cost just a little more than SS, but you may want to consider the design and construction of a double wall SS tank which would be heated with boiling water between the walls. This would provide for a more uniform heating and larger area thus avoiding localized hot spots.