Copper-Induced Metal Release from Lead Pipe into Drinking Water

Abstract

The effect of added cupric ions (0 mg/L to 5 mg/L Cu +2 ) on possible deposition corrosion of lead pipe was investigated in bench-scale experiments under flowing and stagnant water conditions. Under stagnation the presence of cupric ions in the water feeding lead pipes marginally increased lead release into the water, but under continuous recirculation it could increase lead release by orders of magnitude. Other benchscale experiments investigated galvanic corrosion between lead and copper pipes under stagnation, confirming that water chemistry (particularly the chloride-to-sulfate mass ratio [CSMR]) is a controlling factor in either "strengthening" galvanic corrosion and increasing water lead contamination by orders of magnitude (high CSMR water) or "weakening" the galvanic effect with less but still significant contribution to water lead contamination (low CSMR water). Longitudinal water pH measurements along the length of the galvanic rigs revealed a significant pH drop close to the lead:copper junction at relatively short stagnation times in high CSMR water, which is consistent with the observations of higher lead leaching and higher galvanic current measured in that situation.

Impact of treatment on Pb release from full and partially replaced harvested Lead Service Lines (LSLs)

“…Galvanic corrosion between old lead and copper pipes Wang et al, 2012) is a potential explanation for unexplained long-term (>2 months) high concentrations following partial pipe replacements observed in the field (Sandvig et al, 2008;Britton and Richards, 1981). The presence of copper in water passing through the lead pipe has also been associated with higher lead release, possibly due to deposition corrosion or other mechanisms (Hu et al, 2012;Cartier et al, 2012;Triantafyllidou and Edwards, 2011) as well as crevice corrosion in the brass fitting used at the Pb/Cu junction (Clark et al, 2011). However, these results were obtained using new lead pipes and/or fittings, and/or without realistic flow conditions or statistical replication.…”

Effect of connection type on galvanic corrosion between lead and copper pipes

“…A plastic (insulating) connector 1 (example 7 in the photograph) can also be used to interrupt the lead–copper electrical connection. In laboratory studies (Cartier et al, 2012; Hu et al, 2012; Triantafyllidou & Edwards, 2011), these connections have been simulated using an insulating spacer and flexible plastic tubing, which can be operated with lead and copper electrically disconnected (example 2 in the photograph) or externally connected to allow current flow (example 3). The different connectors are expected to affect galvanic corrosion in at least four ways: by breaking the electrical connection between the copper cathode and the lead anode via an insulator or dielectric, by changing the distance between the lead anode and copper cathode of the galvanic cell, by introducing a third metal if a conductive connector is used, and by introducing a crevice. …”

“…Crevice corrosion can occur in a small gap that is sometimes created between the connector and the outside of the lead or copper pipe (Figure 2). The water sitting essentially stagnant in the crevice can become depleted in oxygen, pH can decrease as metal ions hydrolyze, and concentrations of lead and counter ions (potentially aggressive or passivating) can rise to very high levels (Nguyen et al, 2010; Rosenfeld, 1971). The effect of a crevice on corrosion rate is highly dependent on crevice geometry (Rosenfeld, 1971).…”

“…The practice of partial lead service line replacement (PLSLR), which involves replacing a portion of a lead service line with new copper, has come under scrutiny because of concern over elevated lead in water in both the short and long term (Cartier et al, 2012; Giammar et al, 2012; Brown et al, 2011; Triantafyllidou & Edwards, 2011; USEPA, 2011). Longer‐term problems can arise from direct galvanic corrosion between lead and copper pipe or from deposition corrosion from copper onto lead (Hu et al, 2012; Triantafyllidou & Edwards, 2011; Britton & Richards, 1981), and it is widely accepted that the magnitude of the problems might depend on the type of connection between the pipes (Boyd et al, 2012; Giammar et al, 2012; St. Clair et al, 2012; Triantafyllidou & Edwards, 2011; USEPA, 2011). Recent studies (Giammar et al, 2012; Triantafyllidou & Edwards, 2011; USEPA, 2011) have highlighted the need for research to quantify differences in galvanic corrosion performance of available connectors in PLSLRs with copper.…”

Deposition Corrosion of Galvanized Steel in the Presence of Copper

“…A key thermodynamic controlling factor is the potential of the iron surface, which is affected by water chemistry; copper will plate only if the surface potential is below the threshold for plating. 5,21 Objectives. Based on expectations from both thermodynamic and mechanistic experience reported by the plating industry, 33,34 Cu(I) species are expected to plate more readily than Cu(II) species.…”