Thermo-mechanical processing of brass components for potable-water usage increases risks of Pb leaching

The problem of lead contamination in potable water has been a serious concern in different countries. Although the use of leaded welding solder has been banned and brass components used in potable water pipework have to be of the nominally "lead-free" grade in most jurisdictions, incidents of excessive lead leaching are still reported. The widely advocated explanation of lead leaching from brass components in terms of corrosion and the formation of electrochemical cells is inadequate since mechanical cutting is also known to cause lead segregation on brass surfaces. In this study, the effects of lead segregation on brass surfaces and subsequent leaching to contacting water resulting from thermo-mechanical processing of the brass are studied. The results indicate that mechanical milling and polishing that replicate the common processing involved in pipeline installation yield a significant increase in surface lead, and a strong correlation exists between lead leaching and the plastic deformation of the brass surface. Furthermore, flame-torch treatment that replicates the common brazing of brass also results in a significant increase in surface lead. These results indicate that the common thermo-mechanical processing of brass piping components poses a real risk of lead contamination in potable water, and revision in the common protocols for handling lead components may be necessary.