Addressing corrosion control and valve tuberculation in a water distribution system supplied by a silica-laden groundwater

Abstract Metal corrosion and valve tuberculation within a water distribution system supplied by groundwater containing 52 mg/L silica were studied using a corrosion test rack installed within a residence to determine the effectiveness of phosphate-based (PB) and silica-based (SB) corrosion inhibitor (CI). Results indicated that internal corrosion control based on the use of phosphate-based or silica-based CIs did not significantly decrease iron, lead, or copper corrosion rates, and in one case, caused a negative impact on copper corrosion rate. Evaluations of metal coupons using scanning electron microscopy, electron dispersive X-ray analysis, and X-ray photoelectron spectrophotometry confirmed these findings. Since CI failed to reduce corrosion rates, valve tuberculation within the water system could not be controlled. Consequently, a valve replacement plan was developed in place of an internal corrosion control method using CIs. An opinion of probable replacement cost for 200 tuberculated valves approximated $3.3 million expended over 20 years.

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