Processes Controlling the Time for Orthophosphate to Achieve Effective Corrosion Control
The total period of conditioning was more than 60 weeks. The scale has been characterized by optical imaging, electron microscopy, and Raman spectroscopy. The water and scale analysis indicated that the scale was ready to move on to the stage of the experiments in which half of the lead pipes will receive orthophosphate for 1-3 months, followed by a change from free chlorine to monochloramine for all of the pipes. The addition of orthophosphate began in June. A preliminary experiment with two 3-inch lead pipe segments with the PbO2-containing scale indicates that the scale has a strong response to a change to monochloramine with rapid and extensive lead release as PbO2 dissolves.
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