Corrosion-Induced Zinc Runoff from Construction Materials in a Marine Environment

Zinc runoff rates from 11 zinc-based construction materials with and without surface treatments or coatings are presented and discussed in terms of patina formation, seawater deposition, wetting conditions, and changes in corrosion resistance. As opposed to earlier reports, current runoff rates have been assessed in a marine test site (Brest, France) rather than in mainly urban sites. High surface wetting conditions and concomitant removal of deposited chloride and sulfate species are proposed to cause the unexpectedly low zinc runoff rates observed in the marine site, despite a high ISO corrosivity classification for zinc. The average runoff rate for hot dipped galvanized steel after 1 year is and 100 times lower when coated with two organic layers . Organic coatings of varying thickness result in improved barrier properties and reduced runoff rates that seem highly dependent on thickness. Aluminum alloying also results in reduced zinc runoff rates caused by surface areas enriched in aluminum.