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Stagnation Time, Composition, PH and Orthophosphate Effects on Metal Leaching from Brass September 1996
Plumbing products made of brass and similar alloys are the only lead containing materials still installed in drinking water systems and, by law, may contain up to 8 % lead. Brass ranges in metal composition depending on its application. Brass is composed of approximately 60 to 80 % copper, 4 to 32 % zinc, 2 to 8 % lead, s 6% tin, and trace amounts of iron, tin, and cadmium. The relationship between alloy composition and resulting amounts of metal leached from the alloy in drinking water has not been fully established . Better understanding brass corrosion may provide information and guidance to the use of the safest materials for the production of plumbing fixtures, and optimization of corrosion control treatments.
This study examined the effect of alloy composition, pH, orthophosphate, and stagnation time on the metal leached from 6 different brasses and the pure metals that make-up brass (lead, copper, and zinc) in Cincinnati, Ohio, tap water. Results demonstrated that the amount of various metals leached from the alloys corresponded well with the alloy's composition. Leaching of metal components from brass were generally less affected by pH than the pure metals. A pH of 7 .5 and 0.5 to 3.0 mg/L orthophosphate significantly reduced the amount of lead leached from the alloys initially, but had less impact as time continued. Orthophosphate had a minimal impact on copper levels . The impact of stand time was dependent on water quality and alloy composition . This report covers a period from August 1991 to January 1996, and work was completed as of December 1994.