Iron is one of the most overlooked materials in architectural conservation. Its status as a functional construction material, rather than a decorative element, often makes iron the least understood material by architectural conservators. As historic metal becomes increasingly significant in the built environment, new approaches must be developed in order to better predict and understand the corrosion process. The behavior of corrosion has been extensively studied in the engineering and conservation communities, but the two fields have developed different approaches to iron conservation. Typically, engineers classify corrosion on a macroscopic scale, while conservators approach iron on a microscopic level. Both approaches are undeniably useful. There is, however, no middle ground between conservators, engineers, and contractors, to shape better-informed decisions regarding the sustainability, longevity, and integrity of historic iron.
Famous for its role in the Civil War, Fort Sumter is now largely a ruin with few original iron artifacts intact. History has not been kind to the fort and the metal has experienced decades of exposure to the harsh marine climate--burial in sand, and multiple rebuilding campaigns. Three well understood causes of iron corrosion, the atmosphere, context, and the metal's composition, were applied to the architectural iron at Fort Sumter to determine which aspect has the greatest impact. The temperature, wind, and airborne chloride levels were tracked at Fort Sumter to determine the atmospheric corrosivity level. As surrounding materials affect the exposure of embedded metal, each material was compared to see how its composition influenced the historic iron. A selection of iron objects was chosen for further analysis using X-ray fluorescence spectroscopy (XRF), Raman spectroscopy. By studying these aspects of iron corrosion, the National Park Service will be able to form a better understanding of the corrosion of historic ironwork and implement appropriate, sensitive conservation treatments.