Role of temperature, chlorine, and organic matter in copper corrosion by-product release in soft water

Soft, low alkalinity drinking waters tend to cause relatively high copper c orrosion by-product release in plumbing systems. Long-term tests (6-8 month s) in a synthetic, microbially stable soft tap water confirmed that lower p i-Is and higher temperatures increased copper release to water. Soluble cop per release increased at lower temperature and lower pH. Low levels of free chlorine (0.7 mg/L) slightly increased copper release at pH 9.5, in marked contrast to the dramatic reductions in copper release that have been obser ved in soft waters in which Type III pitting corrosion is occurring. Gum xa nthan and sodium alginate produced a microbially unstable water that reduce d the pH and DO during stagnation in pipes - these indirect effects far out weighed their possible role in chelation or other modes of direct attack on copper surfaces. (C) 2001 Elsevier Science Ltd. All rights reserved.