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The Iron Pillar in South Delhi is an example of a very high degree of accomplishment achieved by ancient and medieval Indians in the art of iron production. It is forge-welded, has a high degree of consolidation and a good surface finish. It is the largest hand-forged block of iron from antiquity which still stands today. It is aptly called 'A pillar of the community from the first to the third millennium.'
Its construction and resistance to weathering has fascinated the metallurgical fraternity, not only of India but of the entire world. Three comprehensive books have been penned on the metallurgy of the pillar, two by Prof R BalasubramaniamC1'2] and one by Prof TR Anantharamant3], and numerous other articles and papers have been written.
Prof Balasubramaniam has been researching and publishing on this subject for more than 15 years and has produced several new findings. His hypothesis that the presence of a high phosphorus content is the reason for its corrosion resistance is unchallenged and it appears that, once and for all, he has cracked the mystery related to its resistance to rusting.
While the author of this article is very much appreciative of the invaluable work done by Prof Balasubramaniam on the pillar, some differences of opinion remain. Let us first look at those of his findings which are accepted.
CORROSION RESISTANCE
Bardgett and Stannerst4] carried out a very detailed and thorough study on the reasons for the corrosion resistance of the Iron Pillar but they completely missed out the role of phosphorous. Studies based on simulated tests indicated a corrosion depth 315 times greater than what is actually found on the pillar.
Prof Balasubramaniam put...