Characterization of the microstructural features and the rust layers of an archaeological iron sword in the Egyptian Museum in Cairo (380–500 A.D.)

Abstract

In this paper, a sword is investigated from a collection of archaeological iron swords displayed in the Egyptian Museum from the civilization centered on Ballana and Qustul in Egyptian Nubia (380–600 A.D.). A range of metallographic analytical techniques have been used to characterize the sword’s metallic structure and its rust crust. The results revealed that the sword was made of low-carbon steel and corrosion products formed on the surface are iron sulfate, iron oxides/hydroxides including goethite, maghemite, magnetite, lepidocrocite, akaganeite and ferric chloride. The investigation also revealed that the rust crust constituted of two corrosion layers: a dense layer and a transformed medium. Crystals of soil minerals were clearly observed in the outer corrosion layer. Moreover, several microstructural features were detected, indicating the stage of deterioration and the features of metallurgy of this sword. Furthermore, the obtained results have been used to select appropriate conservation procedures for preventing degradation in the future and ensuring its reliable restoration.