Delhi pillar

The oxide film formed in dry air at room temperature consists of a spinel phase, probably a solid solution of magnetite and maghemite. Such films form on magnetic tapes. They are around 1.5-2.0 nm thick, and in a dry atmosphere, can provide indefinite protection (e.g. the Delhi pillar). Ali and Wood (1969) found that with time and at a relative humidity of 46%, some hematite developed as well. At higher temperatures (200-300 °C) well defined duplex films with an inner layer of magnetite... 

Several large masses of iron are to be seen in India made many centuries ago by welding together small blooms, obtained by the direct process and weighing several pounds each. That such huge masses could be constructed is a remarkable tribute to the skill of the early Indian metallurgists. The most famous of these are the Delhi Pillar, the Dhar PillarJ and the iron beams from the Black... 

A remarkable iron pillar, dating to about A.D. 400, remains standing today in Delhi, India. This solid shaft of wrought iron is about 71/4 m high by 40 cm in diameter. Corrosion to the pillar has been minimal although it has been exposed to the weather since its erection. 

Ancient iron structures sometimes show no sign of corrosion or at most, very little. The clean atmosphere of past centuries may be responsible in that it allowed a very thin adherent layer of oxide to develop on the surface [22], This layer very often protects against even today s increasingly aggressive industrial pollutants Very often the conditions of the initial corrosion are the ones that determine the lifespan of metals [23], A well-known example is the sacred pillar of Kutub in Delhi, which was hand forged from large iron blooms in 410 a.d. In the pure dry air, the pillar remains free of rust traces but shows pitting corrosion of the iron... 

Iron was also known to early Asian civilizations. In Delhi, India, for example, a pillar made out of iron built in 415 Ce still stands. It weighs about 7 short tons (6.5 metric tons) and remains in good condition after nearly 1,600 years. 

Legend hath it that Delhi owes its name to this pillar, the priests giving it that name from dhili loose or unstable. A Hindoo Judge has informed the Author that there is no connection between the two words. The word Delhi most probably means Heart s Delight . 

Figure 8.9 The forged Kutub iron piiiar in Delhi. The pillar is shown to the right in the picture.

Figure 13.12 Iron pillar in the Qutb mosque, at Delhi India... 

At ambient temperature, however, all metals except gold have a thin microscopic layer of oxide. An example of a noncorroding steel structure is the Delhi Iron Pillar (India) which dates from about 400 A.D. It is a solid cylinder of wrought iron 40 cm in diameter, 7.2 m high. The iron contains 0.15 % C and 0.25 % P and has resisted extensive corrosion because of the dry and relatively unpolluted climate. 

The SO4 ion is released again when H2SO4 dissolves in water. SO2 is the main contributor to atmospheric corrosion. Little rusting appears to take place in the absence of SO2. One of the best examples of how metallic objects are protected in the absence of SO2 is the good state of preservation of the famous Iron Pillar at Qutub Minar, in Delhi, India, which is 1600-years old. 

According to Yajurveda (BC 700-300), iron (shyam ayas) was used from 1000 BC, and apparently sara loha (steel) came on the scene around 500 BC. The well known iron pillar at Mehrauli at Delhi, made of a single piece of iron and weighing approximately 6 tons, stands testimony to the metallurgical expertise of medieval era, which could not be matched by even the best iron founders of the west until about 1800 AD. The pillar... 

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