Delhi Iron Pillar New Insights

7/29/2019 Delhi Iron Pillar New Insights

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Delhi I ron Pill ar: New Insights.Delhi: Aryan Books International. Pp.168, figures 33. PriceRs.1800/- ($40/-)by Balasubramaniam

http://www.indianscience.org/reviews/t_rv_balasubramaniam_delhiironpillar.shtml

Delhi's iron pillar (DIP) in the Qutub area has attracted the attention of archaeologists, laymenand metallurgists alike for its rust less property. Various theories have been propounded about itsrust free iron. Only recently Balasubramaniam has carried out more rigorous analyses usinglatest techniques, as a professor of metallurgy in Indian Institute of Technology, Kanpur, thesefacilities were available to him.

Balasubramaniam attributes these anticorrosion properties to significant presence of Phosphorus(P) in the DIP. We will presently see the technical details of his analysis. He also shows that the

maximum corrosion on the DIP occurs near the joint, mainly because of presence of lead.

The book is divided into seven chapters, with one appendix on the technical details on thepresence of phosphorus in ancient Indian irons. The first chapter introduces the DIP and itscomposition. The second chapter deals with the history of DIP which is quite authentic.Balasubramaniam gives even the transcripts of the inscriptions, a discussion of the history andassociation of DIP with Chandragupta II Vikramaditya, which are quite convincing.Balasubramaniam also discusses details of the palaeography of the inscriptions. He agrees withthe date of 410 AD given by the famous epigraphist Hoernele. He also shows that the originallocation of DIP was actually in Madhya Pradesh, in the Udayagiri hills which have beenidentified with Vishnupadgiri. As Chandragupta II was a great devotee of Vishnu, the pillar was

erected in the honour of his favourite God.

In Chapter 3, Balasubramaniam gives the structural details of the DIP; he also shows that thecapital was joined with the pillar by using lead as the joining metal. He also gives a brief historyof lead metallurgy in ancient India.

Chapter 4 discusses the decorative bell capital on the pillar. He also discusses the technology ofshrink fitting methodology as to how the bell capital was fitted to the iron pillar. The author hasillustrated the reconstruction of techniques.

In Chapter 5, Balasubramaniam has reconstructed the manufacturing techniques of the pillar,

which was done through forge welding, and use of inserts. In chapter 6, the author discusses thetechnical details of corrosion resistance of DIP. He has illustrated the discussion with a numberof x-ray diffraction and FTIR spectra and diagrams. The author also did Mossbauer spectroscopyof the rust samples. He shows that the phosphate was crystalline iron hydrogen phosphatehydride. The author also pleads for more detailed scientific studies on various aspects.

In Chapter 7, the author gives the summary of his analysis of DIP. In this chapter he alsodiscusses the Dhar iron pillar and the other iron pillars at Chadira hills, Mandu hills, Mount Abu


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and also some Mughal canons. In the appendix the author has given the technical details andthermodynamic models of the origin of high phosphorous contents in ancient iron pillars. He hasalso compared here the ancient and modern slag. In the appendix he has shown that ancientIndian iron always produced higher phosphorous than modern iron at all temperatures. Heattributes the higher P content in ancient iron to lack of use of lime (CaO) in the flux.

Balasubramaniam summarises his observations as follows:

Several new insights on the Delhi iron pillar have been presented in the present monograph. Thesubject of iron extraction that was practiced in ancient India was briefly discussed and specificattention was focused on the composition and microstructure of iron of the Delhi pillar. Theorigin of high P content in the Delhi iron pillar, in particular, and in ancient Indian iron, ingeneral, has also been addressed.

The identity of king Chandra of the Delhi iron pillar Sanskrit inscription has been criticallyaddressed. The name Chandra firmly establishes that the king was Chandragupta II

Vikramaditya. Numismatic evidence for the short name of Chandragupta II Vikramaditya beingChandra has been provided for the first time by comparing the archer gold coin types of all theGupta monarchs. Arguments have been provided to show that the inscription was notposthumous in nature. The conquests ofChandra corroborate the conquests of Chandragupta IIVikramaditya. Numismatic and archaeological find spots have been analyzed to provide supportto Chandragupta's conquests. The personal religion of Chandragupta II also lends strong supportto his identification as Chandra. The identification of Chandra with Chandragupta IIVikramaditya poses the least contradictions. The locations of Vahlika and Vishnupadagiri havebeen critically analyzed. It is proposed, based on archaeological and historical evidence, thatUdayagiri could be favorably considered as ancient Vishnupadagiri, where the iron pillar wasoriginally erected. Careful archaeological excavations are necessary at Udayagiri to firmly

confirm the original location of the iron pillar.

The various aspects related to the structural features of the pillar have been addressed. A detailedanalysis of the dimensions of the pillar and its decorative bell capital has been presented. Thepresence of lead in various regions of the pillar has been addressed, along which the constructionof the pillar has been explored in detail starting from the pillar bottom. The presence of lead inseveral regions of the pillar has been described and the possible implication for lead presence onthe corrosion of the pillar has also been discussed. A brief discussion on the status of leadmetallurgy in ancient India has been provided.

The various components that comprise the decorative bell capital have been addressed in detailand the joining methodology of the capital parts as well as the capital to the main body of thepillar has been established. Insights on the possible image ofgaruda, which was originallyplaced on the top of the capital, have been provided. The decorative capital of the Delhi ironpillar has been fabricated from individual pieces (that were produced by forge welding and notcasting). The individual pieces that constitute the iron pillar's capital have been intelligentlyshrunk fit on a hollow cylinder in an artistic and aesthetic manner keeping sound engineeringprinciples in mind. It is important to perform careful ultrasound measurements on all the various


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sections of the decorative capital in order to obtain further insights into the shrink fittingmethodology.


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The manufacturing methodology employed to construct the main body of the Delhi iron pillar helucidated. The vertical and horizontal methods of forging for manufacturing the main body of the pilbeen critically compared. Several aspects of the manufacturing methodology (hammering method,method, use of inserts, use of dies, possible handling method and surface finishing operation) hadiscussed. Visual evidences suggest sideways addition of metal lumps with the aid of hand-held hamm

the pillar in the horizontal position. The addition of iron lumps on to the side of the pillar, with the pillain the horizontal direction, appears the likely method of the manufacture of the pillar. The nature of lumps that were forge welded on to the body has been discussed. The use of hand held hammers for theoperation is also established. The ingenious method employed to handle such a large object has alillustrated. The to-and-fro motion of the pillar during the forging operation must have been possible withof handling clamps on the pillar. The rotational motion of the pillar (and also handling) must have been the use of rotating pegs inserted in the bottom and top cross sections of the pillar, and also on the sidepillar. The final surface finishing operations (hot hammering, chiselling and burnishing) produced thesurface and taper of the cylindrical pillar.

The current theories (environmental and material) for the corrosion resistance of the pillar have been c

reviewed. The apparent anomaly of a two-phase (iron and entrapped slag inclusions) heterogeneous struwrought iron of the Delhi pillar possessing superior corrosion resistance has been understood by mixed theory analysis. The nature of the protective passive layer on the corrosion resistant Delhi iron pillar haddressed based on a detailed characterization of its rust. The rust is composed of iron hydrogen phhydrate (FePO 4.H3PO 4.4H2O) in the crystalline form in addition to a-, y-, o-FeOOH and magnetiamorphous form. The process of protective rust formation on DIP iron has been outlined based on analysis. The passive film formation on the Delhi iron pillar has been contrasted with rusting of norweathering steels. The critical factor aiding the superior corrosion resistance of the Delhi iron pillaformation of crystalline iron hydrogen phosphate hydrate, as a thin layer next the metal-scale interfacdrastically lowers the rate of corrosion due to its low porosity content. The formation of protective crphosphate is aided by alternate wetting and drying cycles, which is the important contribution of the atmto the pillar's corrosion resistance. Therefore, the corrosion resistance of the Delhi iron pillar is due to bo(the environment providing alternate wetting and drying conditions) and iron (with its high P content coprotection by the formation of the crystalline iron hydrogen phosphate).

Suggestions have been provided at the end of each of the previous chapters on the studies that neeconducted on the Delhi iron pillar. Scientists from the Indira Gandhi Centre for Atomic Researconducted several scientific studies (in-situ metallography, radiography, sonography and surface pmeasurements) on the Delhi iron pillar in 2001 (IGCAR 2001) and these studies should shed valuable Most importantly, there is an urgent need to replace the lead sheet covering the surface of the pillar in thunderground regions. When the pillar was re-erected by Beglar in the 19th century AD, the stone platfconstructed and a coating of lead was provided on the buried underground surface of the pillar. Thiscoating of lead (of about 3 mm in thickness) was found to be in an excellent state of preservation wburied regions of the pillar was again excavated in 1961 on the eve of the centenary of the ArchaeSurvey of India. However, the buried portion was found covered with rust layers ranging from a few mmm. After removal of the rust scales (Pl. 36a), numerous cavities and corrosion pits were observedsurface. The preliminary treatment of the pillar comprised of elimination of rust, earthy accretions ansoluble salts resulting in the structure shown in Pl. 36b. The holes, cracks and cavities were consolidaprovided a rust preventive treatmen. The lead sheet coating was again provided to the surface for protepillar from direct contact with mortar and the saline soil on the recommendation of the structural con


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and archaeological engineers. This new lead coating was provided much against the wishes of the Chief of ASI (Lal 1996). Therefore, the present corrosion rate of iron in the buried regions is much more thathe exposed surface due to galvanic action with the lead layer, as lead is cathodic with respect (Balasubramaniam 1999b). The iron in the buried underground region is currently subjected to intense corrosion. It has been suggested, first by Lal (1996), and recently by Anantharaman (199

Balasubramaniam (1997b), that the lead coating be removed and replaced with a zinc coating, becauslead, zinc is anodic with respect to iron and therefore would sacrificially protect the iron underneath. Hthis may not be appropriate because zinc corrodes rapidly in saline soils and the soil around the pillcurrent location, is loaded with chlorides and sulphates (LaI1996). It is important to replace this lead coa38) with another suitable coating (epoxy-based coating, especially if the soil is saline, and maybe combincathodic protection) for proper preservation of this important cultural and scientific object (Pl. 3replacement of lead coating with a suitable coating must be addressed at the earliest by excavating the

regions of the pillar.

Although the Delhi iron pillar has been the focus of attention in the present monograph, it must be realithere are several other large ancient iron objects in India. Some of these objects would be briefly review

The study of these objects has not been taken up on a large scale, with the reason probably being theknowledge of these objects. It is anticipated that serious studies in

the future will address these objects.


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Delhi Iron Pillar New Insights

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