Metallurgical pathways of lead leaching from brass

Abstract

AbstractLeaded (Pb) brass components used in water pipeworks are prone to lead leaching following soldering or brazing during installation. Synchrotron radiation X-ray imaging shows that in the initial state of potable-water grade brass samples, Pb exists mainly as isolated or linked-together particles from sub-micron to several microns large. On heating to the usual soldering temperature of ~200 °C, the Pb contents surface rapidly via diffusion pathways involving an interpenetrating Pb–brass structure with orientation relationship (11$$\bar{1}$$ 1 ̅ )α-brass//(220)Pb; [011]α-brass//[$$\bar{1}$$ 1 ̅ 13]Pb. On heating to the usual brazing temperature of 700 °C, the Pb particles melt and expand in volume, with the Pb content forced into the brass lattice preferentially along {101}α-brass planes, forming Pb phase of low sphericity or even large sheets. On immersion in water, the surfaced Pb particles are oxidized to form PbO needles along the normal direction of {$$\bar{2}\bar{2}2$$ 2 ̅ 2 ̅ 2 }PbO planes, which are then easily washed away to cause Pb leaching.