Corrosion inhibiting amine from steam humidification system linked to filmy deposits on laboratory surfaces

After first being occupied in 1999, the Wisconsin Laboratory of Hygiene's environmental testing facility in Madison, WI, began to show filming (deposits) on its interior walls. At first this was thought to be a result of an improperly operating or inadequate air exhaust system that allowed condensing acid fumes to cause corrosion on surfaces. Monitoring demonstrated that acid concentrations in laboratory air were always low and well within safety standards. Applied modifications to the air handling system did not prevent the deposits. Finally, it was deduced that 2-diethylaminoethanol (DEAE), added to the steam humidification system to prevent corrosion within the steam lines and boilers, was reacting with the low levels of acids in the air to form a precipitate that deposited on surfaces. Measurements of DEAE in surface films confirmed the origin of the deposits. As was the case for acids, concentrations of DEAE in the air were low and within allowable health standards. However, the deposits formed were not easily removed and caused the laboratory, involved in ultra trace element testing that necessitated special clean techniques to prevent contamination, to, incongruously, appear poorly maintained. Moreover, the films presented a safety hazard as deposits on glass surfaces, such as fume hood sashes, caused clouding, impairing vision. Because many laboratories are heated and humidified by steam lines, which invariably require the addition of an amine to prevent corrosion, the possibility of this occurrence should be of widespread interest. By treating boiler feed water to a high degree to remove alkalinity (e.g., by reverse osmosis), the amount of amine needed to be added to the system can be reduced and this will minimize the DEAE deposition problem.