Characterization of Egyptian bronze archaeological artifacts

This paper presents the results of in situ non‐destructive X‐ray fluorescence determination of the chemical analysis of a collection of ten bronze statues that are on display at the Egyptian museum of Cairo. The statues are from the late period of the ancient Egyptian history. In addition, destructive technique X‐ray diffraction analysis was applied on 11 damaged archaeological objects to determine the corrosion products and the alloy compositions. Specimens of the latter objects were subjected to metallographic examinations to determine the microstructure of the alloy. Surprisingly, the results indicated that all ten statues and 10 of the 11 damaged objects were made of lead – bronze alloy; the percentage of the lead varied from 3.43 to 18.04, the tin varied from 2.53 to 10.67. The chemical composition of the patina on eight damaged objects is essentially composed of (Cu₂O) cuprite for all objects in addition to other compounds such as (SnO₂) cassiterite in two objects, (PbCO₃) cerussite in three other objects and (Cu₂(OH)₃Cl) atacamite or (Cu(OH)₃Cl) paratacamite in two 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 electrically insulating. Another advantage for using leaded bronze in making statues is being heavy and thus leads to stability. Copyright © 2012 John Wiley & Sons, Ltd.