Preliminary Study on Corrosion Characteristics of Salt-Iron Cultural Relics Unearthed from Nantong

Salt-iron cultural relics with regional characteristics are the witness of the highly developed ancient salt industry in Nantong and other places. In order to understand the corrosion mechanism and factors of these cultural relics, the corrosion products of eight salt-iron cultural relics were analyzed by portable X-ray fluorescence spectroscopy, X-ray diffraction, metallographic analysis, and scanning electron microscopy energy spectrum. The results showed that the materials of the eight samples were mainly gray cast iron. The strip graphite, the reticular phosphorus eutectic in the cast-iron structure, and the mechanical sand burning defects in the casting process were easy to cause the decline of the mechanical strength of these cultural relics, thus inducing cracks, lamellar spalling, and other diseases. The corrosion products of the samples were α-FeOOH, Fe₂O₃, Fe₃O₄, and γ-FeOOH. Two samples were found to contain a high content of harmful rust β-FeOOH. In view of the existence of many cracks in the matrix and corrosion layer, β-FeOOH promoted corrosion and stress corrosion caused by self-weight, it can be seen that these salt-iron cultural relics need urgent conservation treatment.