Effect of zinc and orthophosphate corrosion inhibitors on cement‐based pipes

Abstract

Many water utilities add zinc orthophosphate to treated water to reduce corrosion of plumbing materials within their distribution systems. The significance of zinc as a corrosion inhibitor was examined in bench‐scale tests of concrete corrosion. In waters with low hardness and low alkalinity, zinc orthophosphate provided better corrosion inhibition for concrete or cement‐based pipes than either zinc or orthophosphate alone. Addition of orthophosphate alone was beneficial in reducing the amount of scaling in waters with high hardness and high alkalinity.

Redox gradients in distribution systems influence water quality, corrosion, and microbial ecology

“…The cement coupons in the chlorinated and chlorinated systems increased in mass by as much as 2% consistent with minimal mass loss and possible hydration of the cement (Table S4), consistent with observations of Parks et al (2012). For iron coupons there were noteworthy differences for chlorine versus chloramine with water age, which depended on the observed disinfectant or oxygen levels.…”

Distribution system water age can create premise plumbing corrosion hotspots

“…Such high pH levels are above Past lead corrosion problems; old distribution system the range suitable for orthophosphate inhibition of corrosion Parks et al 2012) and can also result in increased formation of trihalomethanes but lower levels of haloacetic acids (Xie 2003). Unlike the cement SDSs, the pH decreased by as much as 1.3 units in the PVC and iron systems (Table 3).…”

Effect of Corrosion Inhibitors on In Situ Leak Repair by Precipitation of Calcium Carbonate in Potable Water Pipelines

“…) to drive calcite precipitation, which can be described in terms of the calcite solubility product (K sp,calcite = 10 −8. 48 ) and the activities of dissolved Ca 2+ and CO 3 2−…”

“…43−46 The dosage of Zn may also have been reduced, due to recent studies inability to find it contributes to corrosion control of materials including lead, copper and cement. 47,48 However, other water utilities are considering the need to increase the levels of phosphates and Zn to better control lead corrosion. A key point is that there is presently pressure on water utilities to consider both increasing or decreasing corrosion inhibitor dose, and an improved understanding of phosphates holistic impacts on water system performance including scaling is much needed.…”