AWWA JAW30336

This article applies mixed-couple theory to the electrochemistry of the Pb-Sn solder-copper joint and describes a technique for evaluating corrosion acceleration that is induced by galvanic stimulation. The theoretical underpinnings of the analysis are developed, along with an innovative analytical procedure that makes verification of predicted galvanic currents possible. The normal exposure of the soldered joint to water flow rapidly passivates the solder surface and limits galvanic action. After a few days, the ratio of the copper surface to that of the solder is of minimal consequence to corrosion of the solder surface. The pH is an important parameter in determining the rate and extent of passivation of the solder surface, as is the presence of orthophosphate inhibitors. Chlorine residuals are of little importance to the galvanic corrosion process. This research relates to proposed treatment procedures to minimize lead release. Includes 23 references, table, figures.