Theoretical knowledge on Delhi Iron Pillar (DIP) and iron objects produced in the Gupta period (AD300-AD500) is available in the literature.

The literature suggest that the DIP is a composite/cluster/aggregate of various materials like pure iron, carburized iron, slag (consisting of Fe-oxides and SiO2), traces of carbon in slag, and considerable absorption of phosphorous (absorbed in iron and slag).

The presence of slags and oxide particles in the iron matrix and high phosphorous content is believed to enhance the corrosion resistance of iron objects produced in the Gupta period.