Influence of natural organic matter on the corrosion of leaded brass in potable water

Natural organic matter (NOM) affects the rate of metal leaching from the su rface of leaded brass and the morphology of lead-containing corrosion produ cts. SEM data indicate that lead forms a separate phase on the surface of t he alloy. In organic-free water, hexagonal thin plates of hydrocerussite Pb -3(OH)(2)(CO3)(2) accumulate on and near corroding lead islets. NOM inhibit s the growth of the crystals of hydrocerussite and promotes the formation o f an amorphous hydrated surface film. The galvanic coupling of the surface lead phase with the rest of the alloy accelerates its oxidation. The share of lead in the oxidized metal leached from or accumulated on the surface, s ubstantially exceeds that in the bulk alloy both in organic free-water and in the presence of NOM. NOM increases both short- and long-term lead leachi ng. Its effects are most noticeable in the range of dissolved carbon concen trations 0-2 mg/l. (C) 1999 Elsevier Science Ltd. All rights reserved.