Flooded Archaeological Metal Artefacts: Damage Phenomena in Iron Objects from the Centre de Conservation et d’Étude (CCE) in Namur, Belgium

In July 2021, heavy rainfall inundated the entire archaeological storage area of Namur’s Centre de Conservation et d’Étude (CCE, AWaP), impacting part of the metal collection with contaminated water and mud. A selection of iron artefacts was examined to assess the damage and the factors contributing to this deterioration. Corrosion patterns and other surface phenomena were examined both macroscopically and microscopically. In addition to the typical orange pitting and exfoliation of the metallic layer, spherical (and broken) shells of dried droplets, along with liquid and dried phase formations, as well as orange–brown columns or curly corrosion products on the damaged iron surfaces, were observed. Unusual, elongated particles that appeared to grow upwards in a stalactiform corrosion morphology were also noted.SEM–EDX, µRAMAN, and FTIR analyses revealed the presence of pyrrhotite and the active corrosion product akageneite. Great attention was devoted to understanding the interaction between metal corrosion and the materials used to package the archaeological objects, as well as the impact of previous conservation treatments. In particular, in objects wrapped in bubble wrap, the thin layer formed during the ‘weeping iron’ process exhibited extreme forms. Furthermore, unusual white deposits were noted, identified as various forms of CaCO3.This study aimed to gain a deeper understanding of flood damage and subsequent conservation conditions and to reconsider the use of packaging materials for storage.