Probing the Role of Silicates for Corrosion Control in Lead Plumbing
Abstract
Lead service lines and fittings were installed in Canada's drinking water networks until 1986 and currently pose severe health risks. As pipes corrode over decades of use, lead is released into drinking water resulting in dangerous exposure to elevated lead levels. Sodium silicates can be used for corrosion control of lead, however a basic understanding of how they work is lacking. This thesis describes the results of experiments conducted to determine how silicates interact with lead and aluminum in drinking water, using microscopic and spectroscopic techniques. The results show the presence of silicates inhibited Pb2+ carbonates from oxidizing into less soluble Pb4+ oxides. Furthermore, aluminum interacts with silicates resulting in allophane formation on the lead surface and extending into the bulk. Allophane did not protect against lead dissolution. Silicates may not be adequate as a corrosion control option in drinking water systems rich in solid lead carbonate (Pb2+) phases.