Investigation of Chemical Composition, Structure and Corrosion of Ancient Egyptian Bronze Statues

摘要

In situ non-destructive (XRF) chemical analyses of a collection of ten bronze statues that are on display at the Egyptian museum of Cairo were carried out. The statues are from the late period of the ancient Egyptian history. Chemical analysis of the corrosion products, the alloy composition and the microstructure of damaged objects were also investigated. Specimens of the damaged objects were brought from the store of the Egyptian museum. The results indicated that all statues were made of leaded bronze alloy .The chemical composition of the patina on 8 damaged objects is essentially composed of (Cu_2O) for all objects in addition to other compounds such as (SnO_2) in 2 objects , (PbCO_3) in 3 other objects and (Cu_2(OH)_3 Cl) or (Cu(OH)_3Cl) in 2 other objects. The formation of chlorides and carbonate resulted from the interaction between surrounding environment and the alloy. The results of the metallographic examinations indicated a non-homogenous structure and the increase of the lead content increases the globular lead particles. In spite of this condition the galvanic corrosion tendency when the alloy is exposed to moist air or soil is not possible as lead compounds are protective or are electrically insulating. Another advantage for using leaded bronze in making statues is being heavy and thus lead to stability of the bronze objects.