Role of Chloride, Sulfate, and Alkalinity on Galvanic Lead Corrosion

• Published in: Corrosion (Houston, Tex.) Vol. 67; no. 6; pp. 65005 - 65005-9
• Main Authors: NGUYEN, C. K, CLARK, B. N, STONE, K. R, EDWARDS, M. A
• Format: Journal Article
• Language: English
• Published: Houston, TX NACE International 01.06.2011
• Subjects: Alkalinity; Anions; Anodes; Applied sciences; Bicarbonates; Brazing. Soldering; Chloride; Chloride transport; Chlorides; Corrosion; Corrosion effects; Corrosion environments; Corrosion tests; Drinking water; Electrochemistry; Electrodes; Electrolytic cells; Exact sciences and technology; Galvanic corrosion; Joining, thermal cutting: metallurgical aspects; Metals. Metallurgy; pH effects; Precipitates; Sulfates; Transport; Transport equations; Solder; sulfate; Chlorides; Galvanic corrosion; pH; chloride; Sulfates; Soldering; alkalinity; lead
• ISSN: 0010-9312; 1938-159X
• DOI: 10.5006/1.3600449

Effects of chloride, sulfate, and alkalinity on galvanic corrosion were investigated using beaker tests, lead wire electrochemical tests, and lead solder galvanic cells. At relatively high concentrations of lead and low pH values that might be present at the lead anode surface, sulfate forms precipitates with lead while chloride forms soluble complexes, explaining the detriments of chloride and benefits of sulfate during galvanic corrosion in prior research. Considering these factors and transport equations for anions in water, a chloride-to-sulfate mass ratio (CSMR) above 0.77 is predicted to concentrate more chloride than sulfate at the lead anode surface, whereas the converse occurs below this level of CSMR. Bicarbonate can compete with chloride and sulfate transport and buffer pH at the anode surface, providing benefits to lead corrosion.