Letter 7064 Cleaning evaporators  + Is dilute hydrochloric acid the material of choice to descale treatment plant evaporators? It is used once a week in our evaporators. Ernie Moreno - St. Augustine, Fl + Assuming the evaporators are plastic and are not used to handle cyanide solutions, hydrochloric acid sounds to me like a good material to dissolve scale. Ted Mooney, P.E.  finishing.com Brick, New Jersey + Commercial descaling chemicals often also are either citric acid, or phosphoric acid containing. Citric is particularly good for stainless steels, and also gives some residual anti-bacterial effect, as well. If you buy chemicals marketed specificaly for this purpose, there are inhibitors present, not found in the acids normally. W. Carl Erickson - Rome, New York + What kind of scale, or fouling do you expect on this evaporators? When you would apply chemically means to remove such kind of fouling, you need identify the characteristics of fouling, materials included, structures of the evaporators. Hydrochloric acid, even if diluted, is very strong acid which dissolves calcium scale and many kind of inorganic foulings even at low temperatures like ambinient temperature. Hydrochloric acid should be used with corrosion inhibitor. Hydrochloric acid can lead stainless steel to cracking when it cannot be completely drained. When hydrochloric acid is considered to be dangerous or too strong, sulfumic acid, citric acid and other organic acids can be used as alternative. Hiromi Kawaguchi - Tokyo, Japan Dear Reader, please -- Post a question on a different subject.   Answer this question (in non-commercial fashion).

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