EXAFS studies of the chemical state of lead and copper in corrosion products formed on the brass surface in potable water.

EXAFS measurements in the corrosion deposits were performed on Bell Labs-UIUC beamline X16C at the NSLS at Brookhaven National Laboratory in grazing incidence fluorescence mode at room temperature. EXAFS in the reference Cu and Pb metal foils, malachite, cerussite and hydrocerussite were measured in transmission. Sagittally focused second crystal in the double crystal Si (111) monochromator allowed to horizontally focus the beam to the 1 mm size at the sample position. Harmonics were rejected by detuning the monochromator (Si 111) by-20%. Lytle detector was used for fluorescence detection. Ni and Ge filters (3 absorption lengths thick each) were used for Cu K edge and Pb L3 edge XAFS measurements, respectively. Care was taken to ensure that the XAFS signal from corrosion layer only contributes to the total signal. For that, the sample was rotated and XAFS was measured several times and signals were compared until the contribution from the bulk brass vanished. Corrosion products formed on the surface of lead-containing brass were examined using grazing incidence fluorescence EXAFS. The corrosion scales were shown to be comprised by malachite Cux(OH)2CO 3 and hydrocerussite Pb3(OH)2(CO3) 2. The equatorial and axial Cu-O distances in the corrosion deposits were virtually the same as in the reference malachite sample, whereas the disorder in the Cu-O distances in the corrosion products was enhanced. The chemical environment around the Pb atoms in the corrosion deposits was similar to that in hydrocerussite but there was an apparent shortening of the Pb-O nearest neighbor distances in the corrosion deposits compared to those in pure hydrocerussite.