Method to Rapidly Characterize Reduced Lead Corrosion in Phosphate Inhibited Drinking Water Available to Purchase

The 2014 Flint water crisis incited discussion on the legacy practice of utilizing lead in drinking water delivery pipe, and the critical need for sustained phosphate treatment in order to establish and maintain a protective lead film. However, there is a need to develop a method to quickly assess lead corrosion susceptibility and its mitigation by the addition of phosphate in drinking water. A potentiostatic testing procedure has been utilized to characterize the residual corrosion rate of lead in the presence of phosphate inhibitor more rapidly than existing long-term water sampling practices. This method involves electrochemical testing of freshly polished lead samples in representative potable waters simulating drinking water at the open-circuit potential, directly followed by a 6-day anodic potentiostatic hold in quiescent drinking water. The hold potential was selected based on a relatively common galvanic couple potential observed between lead and stainless steel and copper. This simulates common metal pairings in water delivery pipe and therefore represents a high anodic potential that is a near-worst-case scenario of corrosion in these systems. Results demonstrated that this is an effective method for determining the inhibitor-film-influenced anodic behavior of lead and provides a more rapid assessment of whether phosphate mitigates corrosion than long-term water sampling for dissolved lead. The ability to compare data from these tests with and without additions of phosphate enables rapid, and possibly timely, assessment of the effect of phosphate treatment on propensity for lead corrosion in stagnant drinking water. It was found that phosphate did inhibit the corrosion of lead, but not at short times and not linearly with increasing concentration of phosphate but monotonically. This particular set of experiments has a direct application in situations such as encountered in the Flint, Michigan water crisis and when considering new water sources in situations where information on drinking water corrosiveness and inhibitor efficiency is limited. This technique serves as a foundation for further modification as it can be coupled with Pb(II) water sampling and sample interface analysis to assess the complete fate of Pb(II) cations whether incorporated into scales or present in drinking water.