Free Chlorine Can Inhibit Lead Solder Corrosion via Electrochemical Reversal.

Galvanic corrosion of lead-tin solder in copper plumbing can be a major contributor to water lead contamination. Here, we report the electrochemical reversal of the copper-solder galvanic couple, in which the normally anodic solder becomes cathodic to copper via a reaction with free chlorine. This reversal occurred after a few months of exposure to continuously circulating water with relatively low pH and low alkalinity, causing dramatically decreased lead release and the formation of a Pb(IV) scale.