Corrosion studies on Tang dynasty opaque glaze celadon excavated from Qiong kiln, Sichuan, China

As a typical representative of ancient southern Chinese folk kilns , the Qiong kiln, the firing process, and the corrosion behavior of its opaque glaze celadon are of great significance in revealing the deterioration mechanism of Indigenous ceramic materials. In this study, eight pieces of Tang dynasty opaque glaze celadon excavated from the Qiong kiln's Shifangtang kiln site were taken as the research object, and the glaze corrosion morphology and mechanism under the synergistic effect of glaze corrosion characteristics, physical composition and burial environment were systematically investigated by means of the super depth-of-field microscope, scanning electron microscope-energy spectroscopy (SEM-EDS), Raman spectroscopy , and optical coherence tomography (OCT) techniques. The results show that the corrosion behavior of the glaze layer is significantly affected by the composition of raw materials and the firing process: the incompletely fused quartz particles and precipitated augite crystals become the preferred corrosion sites due to the difference in chemical stability at the interface with the glass phase, which leads to the dislodgement of the crystals and the formation of honeycomb-shaped corrosion pits . The geometrical characteristics of the corrosion pits (increased specific surface area compared to the original glaze) accelerated the interfacial ion-exchange reactions while providing deposition channels for inorganic colloids from the environment to form hollow spherical silicate crusts. This study reveals the multi-scale synergistic corrosion mechanism of the crystal phase - bubble pits - iron deposition material in Qiong kiln opaque glaze celadon, which provides a scientific basis for the development of a targeted cultural relics protection strategy. • Air bubbles in the glaze can cause the glaze to become less structurally stable and prone to the formation of corrosion pits. • The presence of corrosion pits increases the specific surface area of the glaze layer and enlarges the corrosion interface. • The glaze surrounding quartz particles and augite crystals in the glaze layer is preferentially corroded.