Periodic Corrosion Phenomenon and Liesegang Pattern—Section Analysis on Two Ancient Bronze Samples

The phenomenon of alternating layered structures of two types of corrosion products is called “periodic corrosion phenomenon”, which has been occasionally found in archaeological excavations of bronze ware corrosion, currently, there is no theoretical explanation for this phenomenon. The “periodic corrosion phenomenon” of two bronze artifacts unearthed in Sichuan, China were taken as an example, metallographic microscopy, SEM-EDS analysis, and Raman spectroscopy analysis techniques were used. It was found that the bands in the CB-1 corrosion of Chengba bronze sample in Sichuan, China were alternating layers of low crystallinity tin corrosion products and high crystallinity cuprite. This pattern of oscillatory bands might be attributed to the Liesegang crystallization cycle of gel rich in cuprite, this gel medium was the uniform amorphous tin corrosion products. The bands in the corrosion of LJB-38 bronze ware in Luojiaba, Sichuan Province were alternating layers of tin corrosion products (including malachite) and cuprite, but did not present any ordered pattern. This might be due to the occurrence of “decupurification” phenomenon, which led to the rapid outward migration of copper and the pseudomorphic structure of (α+δ) eutectoid in casting bronze corrosion destroyed the uniformity of gel fluid.