The heterogeneous nature of the structure of the monument reveals two important points, namely, no heat treatment has been applied and the metal of the pillar has never been in the molten state, probably the last stage in the construction of so large a piece of iron at that date would almost certainly have consisted of the hammer forging together of balls of iron and thereafter repeated re-heating and hammering process to create smooth surface. This must have taken a considerable time to complete. During this time an oxide film would have formed some of which could get hammered into the surface. Slag too would have oozed out and would have joined the scale. Owing to its high heat capacity and high ambient temperature the finished iron would have taken relatively long time to cool leading to a somewhat non-homogenous normalization, the quality of the oxide layer produced by this sequence of operation would in all probability greatly promote the preservation of the pillar in pure and dry climate.
According to the second theory, the protective oxide could have formed from atmospheric exposure. Examination of small pieces of scale obtained from the iron pillar reveals that it consists of approximately 80% of an oxide of iron having the properties of the solid solution phase of mixtures of FeO and Fe2O3. About 10% of this hydrated oxide of iron, approaching Limonite (Fe2O3.3H2O) has also been reported. From the above reports it can be concluded that the scale was apparently formed under conditions of heating with significant extent of atmospheric oxidation occurring at the surface and penetrating along cracks running longitudinally in the scale.
There have also been suggestions that in the past pillar was ceremonially anointed with purified butter. Tghee obtained from the milk of cow would have had a marked effect. A thin coating of linseed oil or lanoline or wool grease is well known to give good protection to steel for some months. If applied regularly and reinforced b the dust and sand which settle on it, it gives a good protective coating to the material underneath. However, the practice of ceremonial anointing would probably have been discontinued during Muslim occupation of the area in 12th century AD.
The great mass of metal might act as a temperature stabilizer, thus reducing condensation of moisture on it. It has already been mentioned that corrosion proceeds during those time when the effective relative humidity on the surface of the metal exceeds the critical value (e.g. 80%). In Delhi, this cannot normally occur during the day or early in the night because the air is very dry, except of course when it rains. During the remainder of the night the temperature slowly drops and because of its high heat capacity, the pillar remains warm and less liable to corrode than the relative humidity of the air would indicate. Just before day break the pillar is for a very short time cooler than air as dry, daytime conditions are quickly reestablished.
So, in brief, it can be concluded that the corrosion resistance property of the Delhi Pillar is due to: (i) the purity of its iron; (ii) high phosphorus; (iii) low sulphur; (iv) absence of any other metal; (v) cinder coating formed on the surface; (vi) better forge welding; (vii) drier and uncontaminated atmospheric condition; and (viii) mass metal effect The presence of second phase particles (slag and unreduced iron oxides) in the microstructure of the iron, that of high amounts of phosphorus in the metal, and the alternate wetting and drying existing under atmospheric conditions, are the three main factors in the three-stages formation of that protective passive film.
When iron mixed/ comes in contact with oxygen, it created iron oxide or what we know as rust. unless you have coated it with a liquid sealer, it should rust
highly purified iron 99.09 percent pure, that hasn't rusted in thousands of years.
Iron oxide (rust) Isn't magnetic. So rusted iron will have less pure iron in it. making it less magnetic.
asoka
Rusted iron is FeO, iron oxide. 63.8 grams FeO (1 mole FeO/71.85 grams)(6.022 X 1023/1 mole FeO) = 5.35 X 1023 atoms of iron oxide -------------------------------------------
This is not pure iron but a special steel.
because i don't know.
When iron mixed/ comes in contact with oxygen, it created iron oxide or what we know as rust. unless you have coated it with a liquid sealer, it should rust
The base of the pillar is tied to its foundations by small pieces of iron. It rises to a height of 7.20 m, with 93 cm buried below the present floor level
corrosion resistance by hydrogen phosphate forming on the high phosphorus content iron
highly purified iron 99.09 percent pure, that hasn't rusted in thousands of years.
Rusted iron is not pure iron; it is an iron oxide.
because the iron pillar did not get rusted after so many years. it is corrosive resistant due to its high phosphorous content
Iron oxide (rust) Isn't magnetic. So rusted iron will have less pure iron in it. making it less magnetic.
Rusted cast iron.
Firuz Shah Tughlak
Rust on iron is a hydrated iron oxide.