Mineralogical Evidence of Galvanic Corrosion in Drinking Water Lead Pipe Joints

Galvanic corrosion as a mechanism of toxic lead release into drinking water has been under scientific debate in the U.S. for over 30 years. Visual and mineralogical analysis of 28 lead pipe joints, excavated after 60+ years from eight U.S. water utilities, provided the first direct view of three dis...

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Bibliographic Details
Published in:Environmental science & technology 2018-03, Vol.52 (6), p.3365-3374
Main Authors: DeSantis, Michael K, Triantafyllidou, Simoni, Schock, Michael R, Lytle, Darren A
Format: Article
Language:English
Subjects:
Anodes
batteries
cathodes
Chlorides
Copper
copper sulfate
Corrosion
Corrosion mechanisms
Drinking behavior
Drinking Water
Empirical analysis
environmental science
Galvanic corrosion
Lead
Lead oxides
Migration
Mineralogy
Minerals
pH effects
Pipe joints
pipes
Reversion
risk
Sulfates
toxicity
United States
Water levels
Water pipes
Water Pollutants, Chemical
Water Quality
Water Supply
Water utilities
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Summary:Galvanic corrosion as a mechanism of toxic lead release into drinking water has been under scientific debate in the U.S. for over 30 years. Visual and mineralogical analysis of 28 lead pipe joints, excavated after 60+ years from eight U.S. water utilities, provided the first direct view of three distinct galvanic corrosion patterns in practice: (1) no evidence of galvanic corrosion; (2) galvanic corrosion with lead cathode; (3) galvanic corrosion with lead anode. Pattern 3 is consistent with empirical galvanic series (lead → brass → copper in order of increasing nobility) and poses the greatest risk of Pb exposure. Pattern 2 is consistent with galvanic battery reversion. The identification of copper-sulfate minerals (Pattern 2), and lead-sulfate and lead-chloride minerals (Pattern 3) in galvanic zones illustrated the migration of chloride and sulfate toward the anode. Geochemical modeling confirmed the required pH drop from the bulk water level to at least pH 3.0–4.0 (Pattern 2) and pH < 5.5 (Pattern 3) in order to form these minerals. Despite joints being over 60 years old, galvanic zones in Pattern 3 were active and possibly posed an important source of lead to drinking water. Importantly, Pattern 3 was not observed in samples from systems representing water qualities favoring PbO2 formation.
ISSN:0013-936X
1520-5851
1520-5851
DOI:10.1021/acs.est.7b06010