Hi Wally,
It is not a one time use, it will continue to work as long as the microbes are alive and eating the sugars in the molasses. Some people report having their tanks freeze over the winter and continue to work the next spring.
The process works due to the microbes eating the sugar. The microbes require oxygen, so once they consume all the oxygen in the water they start pulling it out of the iron oxide (rust). The oxygen in steel is too tightly bound to the steel, so they cannot pull any out, hence no damage to the steel after all the rust is consumed.
Note - The sealed tank is like a rain forest atmosphere. Any steel sticking out of the water into the air will rust AWAY if you leave it long enough. There is a story on the web about a farmer that put a model A frame into a large bath of molasses and then left on vacation. Came back and found the tank (a lined trench) had leaked that the frame was GONE.
Jack - I think you have a great idea. I will bottle some up and bring to Iowa Gas. Care to trade for some Correct Measure Ads?
