Corrosion mechanisms for lead-glazed pottery from Qibi Ming Tomb of the Tang Dynasty in Xianyang, China

Abstract

Six corroded glazed pottery figurines, which excavated from the Qibi Ming Tomb of the Tang Dynasty in Xianyang, were selected to study the corrosion mechanism. Optical microscopy (OM), scanning electron microscopy equipped with energy dispersive X-ray spectrometry (SEM–EDS), Energy X-ray fluorescence spectrometry (EDX), and micro-Raman spectroscopy were applied to analyze the pristine composition of the glaze layer and pottery substrate, the composition and microstructure of corrosion products. The results indicate that lead-glazed pottery figurines are low-temperature PbO-CaO-SiO2 glaze, with Pb as the main flux, and Cu, Fe as the main colorant. The corrosion products include PbCO3, CaCO3, PbCO3·PbCl2, PbCl2, PbO2, and Si-rich layer. There are Aspergillus niger and Aspergillus sclerotiorum on the surface of glazed pottery. These microorganisms produce organic acids and mold spots on the surface of the pottery figurines, which in turn cause corrosion pits to form on the surface of the figurines. Chemical corrosion reactions mainly include dissolution–precipitation, combination reaction, and oxidation reaction. This article describes the corrosion process of lead-glazed pottery figurines and establishes corresponding corrosion models. This study provides new insights into the corrosion mechanism of lead-glazed pottery, which is of great significance for studying pottery corrosion.