Uptake of silicate by pipe scale materials and effects on lead release

The interactions between dissolved silica and corrosion scale on lead pipes such as hydrocerussite (Pb₃(CO₃)₂(OH)₂) and aluminum containing amorphous phases can affect the rates of lead release from the pipes to drinking water. Batch experiments that were well mixed to fully suspend these materials complemented previous experiments that were performed with pipes with intact pipe scales. These experiments focused on chemical interactions between the corrosion scale materials and silicate by decreasing the effect of mass transfer processes associated with solute diffusion into and out of intact scales. The findings from the batch experiments help us understand that the benefits of silicate addition in controlling lead release observed in a previous pipe loop study with pipes with intact scale were primarily due to inhibited diffusion of lead through the scale as a result of silicate uptake and not due to chemical interactions between lead-containing solids and silicate.