A Study on the Corrosion and Microstructure Characteristics of Early Iron Age Bronze Swords Excavated from Sinpung Site in Wanju, Jeollabuk-Do, Republic of Korea

Abstract

The subject of this study was a bronze sword excavated from the early Iron Age area of Sinpung site in Wanju. SEM-EDS, FE-EPMA and Raman Micro-Spectroscopy analysis methods were applied to investigate the manufacturing techniques and corrosion characteristics. The results of the analysis indicated a casting structure composed of both α and α+δ phases. The α phase developed in the form of dendrite, and it seems that no heat treatment was performed. Through the EDS analysis results, the main components of the bronze sword were identified as Cu, Sn, Pb, etc., and it seems that the cooling rate was different depending on the shape of the dendrite, which is the α phase, and the size and distribution of the Pb particles. Regarding corrosion characteristics, the corrosion progressed considerably to the surface, and a high tin corrosion layer was formed, and lead oxide and copper oxide particles were observed between the corroded microstructures. These materials were identified by Raman spectroscopic analysis as Cuprite (Cu2O), Malachite (Cu2CO3(OH)2), Cassiterite (SnO2), Cerussite (PbCO3), Anglesite (PbSO4), and Litharge (PbO). Among them, the presence of nanocrystalline SnO2 confirmed the characteristics of long-term corrosion of bronze artifacts in the burial environment. And, materials such as Cerussite (PbCO3), Anglesite (PbSO4), and Litharge (PbO) were found only in weapons and tools such as bronze sword and spear when compared with previous studies.