Control of lead release from lead-containing materials galvanically coupled with copper or bronze represent a challenge for corrosion engineers and water treatment practitioners. Currently available data show that in some situations galvanically coupled lead remains passivated and releases little metal while in other cases, for instance those associated with changes of ambient water chemistry, previously passive coupled lead becomes active with resultant episodes of elevated lead release.

While this problem has been thoroughly investigated on a phenomenological level, current understanding of the electrochemistry of galvanic stimulation of lead corrosion and release in drinking water remains insufficient. The goal of this study was to quantify changes of the open circuit corrosion potential (E_corr(x)) across lead/copper interfaces as a function of the distance from the galvanic juncture and concentrations of background salts such sodium chloride, carbonate and others. The theory developed by Song et al. 2010 provides a detailed mathematical description of the distribution of E_corr across galvanic interfaces but this theory has been developed and rested for systems that are notably different from those typical for drinking water. Measurements of trans-galvanic interface E_corr profiles performed in this study showed that E_corr(x) profiles conformed to predictions made based on the existing theory and the effective length of the longitudinal penetration of ionic currents increased as a square root of solution conductivity. The effective length of the coupled ionic currents was notably different for copper and lead. The data demonstrate that short- and long-term changes of properties of ambient water can cause E_corr(x) to undergo considerable changes. This can potentially induce shifts of the galvanically affected zone in which accelerated lead release takes place. Further studies are needed to examine actual effects of such E_corr(x) shifts on spatially localized lead release from galvanically coupled lead-containing materials.

Song, G. L. (2010). Potential and current distributions of one-dimensional galvanic corrosion systems. Corrosion Science, 52(2), 455-480