Rusting of Iron: Introduction, Chemical Reaction

Rusting of Iron: We all must have come across some rusty material or iron while wandering outside. The reddish colour on the metal is called rusting of iron. When iron metal is exposed to air for a long time, it oxidises and forms a reddish-brown colour iron oxide on its surface. This red-brown substance is known as rust, and the process of forming rust is known as rusting.The iron rusting formula is 4Fe + 3O2 + 6H2O → 4Fe(OH)3. Activities such as interaction with less-active metals, acids, iron stresses, and the presence of rust itself frequently speed up the process.

In this article we have provided detailed information on rusting of iron, rusting of iron is an example, rusting process, rusting of iron reaction etc. continue reading this article to get more information on this and make no mistakes while answering questions related to rusting of iron.

Rusting of Iron: Overview

Rusting is the phenomenon of the deposition of a reddish-brown coating on the surface of iron by the action of moist air, and the reddish-brown coating is known as rust. In simple words, when an iron object is left in damp air for a considerable time, it gets covered with a red-brown flaky substance called rust. This phenomenon is called rusting.

The most common example of metallic corrosion is rusting of iron and steel. Many well-known examples include the rusting of exhaust systems and car bodies, water pipes, and various types of structural steelwork.

Iron rusts due to the combined action of air and water on iron. Rusting does not occur in completely dry air or pure air of water. The precise composition of the rust is determined by atmospheric conditions and the relative contributions of the factors that govern rusting. It is primarily composed of hydrated ferric oxide, so the chemical formula of rust is ({\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}{\rm{.x}}{{\rm{H}}_2}{\rm{O}}). The following reaction can roughly describe its formation:

In the presence of moist air, the outer surface of iron rusts first, and a layer of hydrated ferric oxide (rust) is deposited on the surface. This layer is soft and porous, and it may fall off if it becomes too thick. This exposes the lower layers of iron to the environment, causing them to rust. The process continues, and iron gradually loses strength.

Rusting of Iron: Rusting process

Rusting of iron is an oxidation reaction. During rusting of iron, the iron metal reacts with oxygen in the air in the presence of water to form hydrated iron \(\left( {{\rm{III}}} \right)\) oxide, \({\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}{\rm{.x}}{{\rm{H}}_2}{\rm{O}}\).

Rust is the name given to this hydrated iron (Ill) oxide. As a result, rust is primarily hydrated iron \(\left( {{\rm{III}}} \right)\) oxide, \({\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}{\rm{.x}}{{\rm{H}}_2}{\rm{O}}\). Rust is a reddish-brown colour. We have all seen red-brown rust on iron nails, screws, pipes, and railings here and there. Not only does iron rust, but steel rusts as well when exposed to damp air. Steel, on the other hand, rusts less easily than iron.

Rusting of Iron is a Chemical Change

Rust is iron oxide \(\left( {{\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}} \right)\). Rust is something which is deposited on iron and they are not the same. Rusting of iron is a chemical change because a new substance called ‘iron oxide’ is formed during this process.

The Conditions Necessary for Rusting of Iron

Both oxygen and water must be present for the rusting of iron to occur. So, the rusting of iron is caused and governed by the following factors:

1. Presence of air
2. Presence of moisture

Experiment to Prove that Air and Moisture are Essential for Rusting

Procedure to demonstrate that rusting requires moisture and air.

1. Place clean iron nails in each of three test tubes labelled \({\rm{A}},\,{\rm{B}}\), and \({\rm{C}}.\)
2. Pour some tap water into test tube \({\rm{A}}\) and cork it.
3. Pour boiled distilled water into test tube \({\rm{B}}\), then add about \(1\,{\rm{ml}}\) of oil and cork it. The oil will float on the water, preventing the air from dissolving.
4. Place some anhydrous calcium chloride in test tube \({\rm{C}}\) and cork it. If there is any moisture in the air, anhydrous calcium chloride will absorb it.
5. Allow these test tubes to sit for a few days before observing.

Observation

It is observed that iron nails rust in test tube \({\rm{a}}\) but not in test tubes \({\rm{b}}\) and \({\rm{C}}\). Because the nails in test tube \({\rm{a}}\) are exposed to both air and water, therefore, the nails become rusted. The nails in test tube \({\rm{b}}\) are only exposed to water, while the nails in test tube \({\rm{C}}\) are exposed to dry air.

Conclusion

This experiment shows that both air (oxygen) and moisture are essential for rusting to take place.

Rusting Damages Iron Objects

Rust is soft and porous, and it slowly falls off the surface of a rusted iron object, causing the iron beneath to rust. Thus, iron rusting is a continuous process that slowly eats away at iron objects, making them useless. Because iron is used to make a wide range of objects and articles, such as bridges, grills, railings, gates, and the bodies of cars, buses, trucks, and ships, rusting of iron causes significant loss over time. It is self-evident that we should have some means of preventing iron from rusting.

How do we Prevent Rusting of Iron?

The wasting of iron objects due to rusting causes a significant loss to the country’s economy and must be avoided. Several methods are used to protect iron objects from rusting. The majority of the methods involve coating the iron object with ‘something’ to keep out air and water. The following are some of the most common methods for preventing rusting of iron:

1. Rusting of iron can be prevented by painting: The most common method of preventing the rusting of iron is to coat its surface with paint. When the paint is applied to the surface of an iron object, air and moisture are prevented from coming into contact with the iron object, and thus rusting does not occur. Window grills, railings, iron bridges, steel furniture, railway coaches, and the bodies of cars, buses, and trucks, among other things, are all painted regularly to keep them from rusting.
2. Rusting of iron can be prevented by applying grease or oil: When some grease or oil is applied to the surface of an iron object, then air and moisture cannot come in contact with it, and hence rusting is prevented. For example, to avoid corrosion, iron and steel tools and machine parts are rubbed with grease or oil.
3. Rusting of iron can be prevented by galvanisation: Articles that are exposed to extreme moisture, such as roof sheets and pipes, are protected from Rusting by galvanising. Galvanization is the process of coating steel and iron with a thin layer of zinc to prevent rusting. The iron coated with zinc is called galvanised iron. As zinc is more reactive than iron, it reacts with oxygen in the presence of moisture to form an invisible layer of zinc oxide which protects it from further Rusting. It is interesting to note that galvanised iron articles remain protected from rusting even if zinc coating is broken. This is because zinc is more reactive than iron.
4. Rusting of iron can be prevented by electroplating: Another technique used to prevent articles from rusting is electroplating. Metals that do not corrode, such as tin, nickel, and chromium, are electroplated on iron in this process. This process not only prevents rusting but also improves the appearance of the articles. Some of the articles that are chromium-plated are bathroom fittings and vehicle parts such as bicycle handlebars, car bumpers, and so on.
5. Rusting of iron can be prevented by alloying it to make stainless steel: When iron is alloyed with chromium and nickel, stainless steel is formed. Stainless steel does not rust at all. Cooking utensils, scissors, surgical instruments, etc., are made of stainless steel and do not rust at all. However, stainless steel is too expensive to be used in large quantities.
6. Rusting of iron can be prevented by tinning: Tin is non-toxic and has a lower reactivity than iron. Food cans are tinned, which means they are thinly coated with tin. So, when a thin layer of tin metal is deposited on iron and steel objects by electroplating, then the iron and steel objects are protected from rusting. Tin-plated tiffin boxes are used because they are non-poisonous and do not contaminate the food stored inside.
7. Rusting of iron can be prevented by Enameling: Enameling is a process by which powdered glass is fused to a metal substrate at high heat. Enamels can be applied to glass-ceramics.

Rusting of Iron: Summary

Rusting of iron is the deposition of a reddish-brown coating on the surface of iron by the action of moist air. This reddish-brown coating is known as rust and is called hydrated iron \(\left( {{\rm{III}}} \right)\) oxide, \({\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}{\rm{.x}}{{\rm{H}}_2}{\rm{O}}.\) The condition necessary for rusting of iron is the presence of air and presence of moisture. Rusting of iron can be prevented by applying a coating of paint, grease and oil, galvanisation, etc.

FAQs on Rusting of Iron:

Here are some of the frequently asked questions on Rusting or Iron:

Q.1. What is the process of rusting of iron?
Ans: Rusting of iron is an oxidation reaction. During iron rusting, the iron metal reacts with oxygen in the air in the presence of water to form hydrated iron \(\left( {{\rm{III}}} \right)\) oxide, \({\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}{\rm{.x}}{{\rm{H}}_2}{\rm{O}}.\) Rust is the name given to this hydrated iron \(\left( {{\rm{III}}} \right)\) oxide. As a result, rust is primarily hydrated iron \(\left( {{\rm{III}}} \right)\) oxide, \({\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}{\rm{.x}}{{\rm{H}}_2}{\rm{O}}.\) Rust is a red-brown colour.

Q.2. What is rusting of iron called?
Ans: Rusting is the phenomenon of the deposition of a reddish-brown coating on the surface of iron by the action of moist air, and the reddish-brown coating is known as rust.

Q.3. What is rust? Give the equation for the formation of rust?
Ans: When iron metal is exposed to air for a long time, it gets oxidises and forms a reddish-brown colour iron oxide on its surface. This red-brown substance is known as rust.
The equation for the formation of rust is;

Q.4. What is rusting of iron with example?
Ans: Rusting is the phenomenon of the deposition of a reddish-brown coating on the surface of iron by the action of moist air, and the reddish-brown coating is known as rust. Examples:

Many well-known examples include the rusting of exhaust systems and car bodies, water pipes, and various types of structural steelwork.

Q.5. How rusting of iron can be prevented?
Ans: Rusting of iron can be prevented by
a. applying paint
b. applying grease or oil
c. by galvanisation
d. by electroplating
e. by alloying iron to make stainless steel
f. by tinning
g. by Enameling

Study About Oxidation and Reduction

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