CORROSION OF COMMON BIRD SHOT TYPES IN NORTH CAROLINA ENVIRONMENTS

Studies of lead shot corrosion in shooting ranges to ascertain impacts on the environment and to better understand the process of lead corrosion have been well documented in the scientific literature. However, these studies have not evaluated other types of shot nor described corrosion behavior in environments other than well aerated soils. This study compared corrosion of lead, copper-coated lead, steel, 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, barrier island lagoonal mud, brackish water, running (stream) freshwater above and below sediment surface, still (pond) freshwater above and below sediment surface, and forest soil and surface. Through approximately 4.5 years exposure, samples were periodically collected and analyzed with scanning electron microscopy, energy dispersive spectrometry, and powder X-ray diffractometry. Corrosion products were mostly oxides and carbonates from these environments except for the lagoonal muds, which also produced carbonates, sulfides, and sulfates. Samples in environments that contained sediments immersed in water were the most severely corroded while samples that were at or above the water table were least corroded. Initial analyses reveal lead oxide corrosion in lead and copper-coated lead shot. Steel and tungsten steel had a layer of iron oxides. Bismuth shot had very little corrosion in many environments.