The Iron Pillar is located in the Qutub Mīnār complex. It was likely created in a horizontal position using the forge welding technique, which involves using intense heat to combine lumps of iron weighing 40–50 pounds (18–23 kilogram) apiece. The capital was constructed from seven individual parts. They were fitted over a hollow cylinder that was then inserted into the body of the pillar There are two areas of interest to scholars who have studied the iron pillar: (a) inscriptions in the pillar dating to the 4th century and (b) its rust-free metallurgical properties
The six-ton pillar has an inscription in Sanskrit language and Brahmi script, dating to the 4th century, stating that it is erected as a flagstaff in honour of Vishnu to celebrate the victory of the Gupta king, Chandra. This almost certainly refers to Chandragupta II (375-413), the third ruler of the Gupta empire in India. The pillar carries a variety of inscriptions from various periods, including a later inscription that “in Samvat 1109 (1052-53 CE) Anangpala founded Dehali”.
The pillar was probably made in Udayagiri, Vidisha (in Madhya Pradesh) or Mathura (in Uttar Pradesh) and there may have been a figure of Garuda, the eagle-form vehicle of Hindu God Vishnu, at its peak. Some historians believe that it was shifted to Delhi as a trophy, on the orders of Sultan Iltutmish around the 13th century after he conquered Udayagiri. Others aver that the pillar was moved to a temple in Lal Kot, Delhi by King Anangapala of the Tomar Rajput dynasty in 1050 and then moved to its current position in the Qutub Minar complex in 1191.
The iron pillar is rust-free despite having been built more than 1,600 years ago. The factor contributing to the superior corrosion resistance of the iron pillar is the formation of iron hydrogen phosphate hydrate, as a thin layer next to the metal–metaloxide interface. This is aided by alternate wetting and drying cycles (i.e. the environmental factor). The rate of corrosion is further lowered due to the low porosity content of the crystalline phosphate phase. The Jain text, Pasanahachariyu (1132 CE) states that the pillar was so mighty and magnificent that “the weight of the pillar caused even the Lord of the Snakes to tremble”