## 4 Conclusions  
This study analyzed the metallurgical and corrosion characteristics of Early Iron Age bronze mirrors excavated in the Sinpung site in Wanju. According to the ICP-AES results, the bronze mirrors were cast with a triple bronze Cu-Sn-Pb alloy (60% to 65% Cu, 25% to 28% Sn, and 0.85% to 1.21% Pb). Their metallic microstructures consisted of an \(\delta\) phase and an \(\alpha\) + \(\delta\) eutectoid phase, and there was no evidence of further treatment after casting. Lead sulfide was observed in the microstructure of the Ga-35 (No. 3) bronze mirror, suggesting that its lead content originated from lead ones used to produce the artifacts. Sulfides containing Fe from copper sulfide ore or Cu-Fe-S residual matte were also added to the bronze mirrors while being manufactured. Figure 13: (**a**) Ga-35 (No. 3) electron probe microanalyzer (EPMA) image and (**b**) line analysis. For corrosion characteristics, selective corrosion in the \(\alpha+\delta\) eutectoid phase was observed at the sample's surface, where selective corrosion in the \(\alpha\) phase was correlated with the oxidation environment. In contrast, selective corrosion in the \(\alpha+\delta\) eutectoid phase was correlated with a reducing burial environment [8]. According to [PERSON] et al. 's classification system [9], Ga-2 and Ga-35 contained corrosion materials classified as type I corrosion. Meanwhile, nanocrystalline SnO\({}_{2}\) observed in bronze mirrors buried for long periods in soil was observed in type I and type II corrosion. High-purity secondary copper in the artifacts was mainly located in cracks, holes left by Pb corrosion, and the corroded \(\alpha+\delta\) eutectoid phase. The secondary copper was classified according to [PERSON] and [PERSON]'s [8] proposal as it followed similar patterns. They distinguished the formation mechanism of secondary copper into two types: redeposition and destannification. In metallic copper formed through the former, Cu ions could not move freely and form metallic structures. In the samples, metallic copper was found in cracks, holes, and between cuprite formations formed through redeposition. In comparison, metallic copper formations found as pseudomorphs on the \(\alpha+\delta\) eutectoid phase formed through destabilization because copper moved inward and replaced the existing metallic structures following Sn's selective corrosion. Thus, the secondary copper observed in holes left by corroded Pb particles and cracks on the excavated mirrors formed through redeposition. In contrast, the secondary copper formations observed on the \(\alpha+\delta\) eutectoid phase were created through destabilization. Various analytical techniques were used on bronze mirrors excavated from the Sn-pung site to identify their production techniques and corrosion characteristics. Compared to other artifacts excavated from the site, weapons (swords) and tools (plows) contained Pb oxides, such as cerussite (PbCO\({}_{3}\)), anglesite (PbSO\({}_{4}\)), and litharge (PbO), as corrosion products, which were absent in bronze mirrors [17]. This contrast shows that the mirrors exhibited different corrosion characteristics caused by differences in alloy compositions or production techniques. The presence of malachite, which does not form in an underwater burial environment, indicated that corrosion characteristics could only be found in bronze mirrors excavated from the ground [18]. The corrosive properties of pure bronze artifacts also showed a heterogeneity that cannot be simulated in an artificial environment. Therefore, this study's results are of great importance for preserving artifacts and evaluating an artifact's authenticity. Moreover, future studies must develop a multifaceted analysis of various bronze artifacts and develop a comprehensive understanding of burial environments to establish long-term corrosion mechanisms in ancient bronze artifacts. Conceptualization, N.C.C. ; methodology, I.K.H. ; software, I.K.H. ; validation, N.C.C. ; formal analysis, M.K.J. ; investigation, I.K.H. ; resources, M.K.J.