Corrosion of ancient Chinese bronze money trees studied by Raman microscopy

Abstract

Raman microscopy was used to identify corrosion products and their locations on and within samples from ancient Chinese bronze money trees to help determine the corrosive environments the trees experienced in the past. The compounds found included Cu2 O, CuCO3 · Cu(OH)2, 2CuCO3 · Cu(OH)2, PbO, PbCO 3 and PbSO4. In addition, a number of pigments on the exterior were identified (ultramarine, Prussian blue, phthalocyanine blue, phthalocyanine green, Hansa yellow G and chrome yellow) which were applied to the artifacts in more recent times. Two-dimensional Raman mapping was applied to cross-sections of the artifacts to determine the spatial extent of corrosion products in the interior and to investigate the selective corrosion of different phases of the bronze. Raman microscopy is shown to be a useful tool to complement more traditional characterizations such as scanning electron microscopy and x-ray energy-dispersive spectrometry in the analysis of metal artifacts. Copyright © 1999 John Wiley & Sons, Ltd.