Melt rust?

fleabag

Banned
Oct 1, 2007
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Can oxidized Iron (I.E Rust) be converted back into iron just by melting it? I mean if I had 10lbs of rust in a bucket, could I convert that into an iron block?
 

Cogman

Lifer
Sep 19, 2000
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essentially that is how they smelt Iron ore in the first place

from the wikipedia under Iron Ore
Main articles: blast furnace and bloomery

Iron ore consists of oxygen and iron atoms bonded together into molecules. To convert it to metallic iron it must be smelted or sent through a direct reduction process to remove the oxygen. Oxygen-iron bonds are strong, and to remove the iron from the oxygen, a stronger elemental bond must be presented to attach to the oxygen. Carbon is used because the strength of a carbon-oxygen bond is greater than that of the iron-oxygen bond, at high temperatures. Thus, the iron ore must be powdered and mixed with coke, to be burnt in the smelting process.

However, it is not entirely as simple as that; carbon monoxide is the primary ingredient of chemically stripping oxygen from iron. Thus, the iron and carbon smelting must be kept at an oxygen deficient reduced state to promote burning of carbon to produce CO not CO2.

Air blast and charcoal (coke): 2C + O2 \to 2CO.
Carbon monoxide (CO) is the principal reduction agent.

Stage One: 3Fe2 O3 + CO \to 2Fe3 O4 + CO2
Stage Two: Fe3 O4 + CO \to 3Fe O + CO2
Stage Three: FeO + CO \to Fe + CO2

Limestone fluxing chemistry: CaCO3 \to CaO + CO2
 

gorcorps

aka Brandon
Jul 18, 2004
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You don't just have to melt it, you have to keep it in the temperature ranges where the CO2 reactions are more stable than the CO reactions and basically go about things the way Cogman found.
 

edcarman

Member
May 23, 2005
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0
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No, you can't just melt it. You need to heat it in a reducing environment.

The reducing environment is provided by some material that will will strip the oxygen away from the iron atoms. In most smelting operations this material is carbon, while in a thermite reaction it is aluminium.

The heat is needed to provide the energy to start and sustain the reduction reaction. In thermite, the initial heat can be provided by a magnesium ribbon or blowtorch, whereafter the reaction is self-sustaining. In a blast furnace, the heat is mainly provided by burning coke to form CO which then reacts with the ore, as shiwn by Cogman. In other smelting operations, it can come from electric heating, gas burners etc.