Investigation of the altered layer on ancient Chinese bronze mirrors and model high-tin bronzes

Many ancient Chinese bronze mirrors have a smooth patina. An ingress of corrosion to a depth of approximately 100 {mu}m is found beneath the patina. The corrosion selectively replaces the Cu-rich {alpha} phase leaving the Sn-rich {delta} phase intact. Previous work by x-ray diffraction has shown that the {alpha}-phase replacement product is poorly crystallized or nanocrystalline SnO{sub 2}. Transmission electron microscopy was employed to further characterize the replacement product in both ancient mirror and replication samples. Nanocrystalline SnO{sub 2} in the form of small spheroids has been found. Remnants of an original alloy phase appear to be interspersed with the tin oxide