Delhi iron pillar rust characterization by x-ray diffraction analysis

Rust samples obtained from the region just below the decorative bell capital of the Delhi iron pillar (DIP) have been analyzed by x-ray diffraction (XRD). The identification of iron hydrogen phosphate hydrate in the crystalline form was unambiguous. The stability and formation of crystalline iron hydrogen phosphate hydrate is briefly addressed. Very weak diffraction from the oxyhydroxides/oxides of iron was found. These phases are most likely present in the amorphous form in the rust. The present XRD analysis of rusts obtained from an inaccessible area of the DIP are compared with earlier analysis of DIP rust obtained from the region accessible to the public.