CORROSION MINERALOGY OF COMMON BIRD SHOT TYPES IN NORTH CAROLINA, USA, ENVIRONMENTS

This study compared corrosion of lead, steel, copper-coated lead, tungsten-steel, and bismuth varieties of shot in different sedimentary and aquatic environments in North Carolina. Sets of individual plastic vials containing all five types of shot were placed in the following environments: marine beach, marine dune/soil, bather island lagoonal mud, saltwater, running (stream) freshwater above and below sediment surface, still (pond) freshwater above and below sediment surface, and forest soil and surface. After approximately 4.5 years exposure, samples were collected and analyzed with scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) and powder X-ray diffraction (XRD). Samples that were placed in saltwater environments were the most severely corroded, while those in terrestrial or freshwater environments were much less corroded. Similarly, buried samples were generally more corroded than samples placed at or above the water table. Analyses reveal the production of Pb oxide, hydroxide, chloride, carbonate, sulfide, and sulfate compounds in lead and copper-coated lead shot. Steel and tungsten-steel shot exhibited a surface layer of Fe oxides/hydroxides. Bismuth shot and tungsten-steel shot showed little corrosion, limited to small amounts of oxide/chloride and oxide only in two of the sampled environments. In all shot types, 19 minerals and one non-mineral compound [Zn-4(CO3)(OH)(6)center dot H2O] were identified as corrosion products.