Understanding the Unique Corrosion Phenomenon of Sanxingdui Embrittled Gold Masks Using Scanning Electrochemical Cell Microscopy (SECCM): Intergranular Corrosion of Au-Ag-Pb Ternary Alloy
作者
单位
1Center for the Study of Chinese Archaeology、School of Archaeology and Museology、Peking University、Beijing 100871、China. 2Key Scientific Research Base of Scientific & Technological Evaluation (Beijing University of Chemical Technology)、National Cultural Heritage Administration、Beijing 100029、China. 3Key Laboratory of Archaeomaterials and Conservation、Ministry of Education、Institute for Cultural Heritage and History of Science & Technology、University of Science and Technology Beijing、Beijing 100083、China.
关键词
收录来源
International Corrosion Congress · 第22届国际腐蚀大会
摘要
This research was prompted by the discovery of unusual corrosion in a series of archaeological gold masks crafted from 50 – 100 μm thick gold foil and unearthed from the Sanxingdui archaeological site in Sichuan, China. Despite the prevailing assumption that gold artifacts are corrosion-resistant and malleable, some of the gold masks unearthed in 2023 exhibited brittle and fragile characteristics. Morphological studies employing metallographic microscopy and scanning electron microscopy with energy-dispersive spectroscopy (SEM -EDS) revealed the presence of intergranular cracks and attributed the embrittlement to preferential corrosion of intergranular Pb - containing phases. Simulated samples of the Au -Ag-Pb alloy with compositions and microstructures similar to those of the ancient artifacts were created, exhibiting three main microscopic constituents: The Au -Ag continuous phase, the Au 2Pb phase, and the AuPb2 phase intermingled with reticular Pb oxides. Scanning electrochemical cell microscopy (SECCM ) technology was employed to conduct a quantitative analysis of simulated Au -Ag-Pb alloy samples to compare the electrochemical properties of the different phases at the microscopic level. Tafel analyses were performed for each testing spots. The results revealed an electrochemical activity order of AuPb 2+PbxOy >> Au2Pb > Au -Ag, which elucidated the varying levels of retention observed for different components in gold masks. The AuPb2+PbxOy phase was the phase with the highest corrosion priority. Despite t he relatively low electrochemical activity observed in the Au2Pb phase, it demonstrated a notable advantage in activity compared to the Au -Ag phase. This finding aligns with the long-term corrosion observations observed in the gold mask samples. The study provides a reference for subsequent protection strategies and shows the importance of corrosion inhibition in Pb -containing phases. It also demonstrates the potential of SECCM in analyzing and conserving metal artifacts.