Effects of varying temperatures and alkalinities on the corrosion and heavy metal release from low-lead galvanized steel.

The presence of galvanized pipe in drinking water distribution systems is known to be associated with heavy metal release, especially after the aging of zinc coating. This study examined release of lead and other heavy metals (e.g., cadmium, chromium) from galvanized steel coupons with a low-lead zinc coating. Metal release data were obtained in 12-week long jar tests which were conducted at varying temperatures and alkalinities. The morphology of the exposed surfaces was dominated by spherical and acicular formations. Exposures at 36 °C were associated with increased corrosion rates, accelerated depletion of zinc coating and faster development of corrosion scales, compared with 4 and 20 °C. The protective action of zinc coating was enhanced at increasing alkalinities. Metal release data showed a significant enrichment of Pb and Cd levels in the particulates released from the low-Pb galvanized steel.