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What is Rust?

When iron is exposed to water or air over a period of time, the iron reacts with oxygen in the presence of moisture to form a reddish-brown chemical compound, iron oxide. This is referred to as rust. So chemically, rust is hydrated iron(III) oxide or Fe2O3.nH2O. The chemical equation for the same is given by:

4Fe(OH)2 + O2 + xH2O → 2Fe2O3.(x+4)H2O

Iron reacts very readily with oxygen. This is one of the reasons as to why it is rare to find pure iron in nature.

Factors Affecting Rusting

There are several factors that assist and accelerate the process of rusting. Some of them are:

  • Moisture: Iron exposed to rains is the most common reason.
  • Acid: It accelerates rusting. When exposed to acid rains, iron rusts faster. On the other hand, alkalis inhibit rusting.
  • Salt: Iron tends to rust faster in sea, due to the presence of salt.
  • Impurity: Pure iron rusts slower than the iron mass which contains a mixture of metals.

Why Rust Prevention?

Rusting makes iron flaky and friable and decreases its intended usage period. The strength, appearance and permeability degrade which leaves the rusted iron useless. A considerable amount of damage is done by rusting every year, which includes damaging of cars, grills, buses, railings, sinking of ships, falling of bridges, deterioration of statues, etc. Huge sums of money is spent for the replacement and repair of these damages. Thus, it is important to take steps to prevent iron from getting rusted.

Preventive Measures

As we have seen earlier, the prime cause of rusting is the exposure of iron to water and air. So, if we don’t let the surface of iron to come in direct contact with them, we can prevent rusting. Some effective measures used to prevent rusting are:

  • Coating and painting: Iron surface is often painted with the coatings of varnish or paint to isolate it from the environment. Window grills, bodies of automobiles, iron bridges and rails are painted regularly to protect them from rusting.
  • Applying a layer of grease: Grease or a layer of oil is also applied to iron surfaces, primarily on machines and industry tools. This serves dual purpose of a lubricant reducing friction as well as rust prevention.
  • Galvanisation: It is a process of depositing a thin layer of a non-reactive metal like zinc on the surface of iron. This metallic layer prevents the iron to come in contact with air and moisture. Buckets, drums, roofs, pipes etc. are galvanized to prevent rusting.
Rusting And Factors Affecting Rusting - Class 7

Galvanisation of Iron

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FAQs on Rusting And Factors Affecting Rusting - Class 7

1. What is rusting and how does it occur?
Ans. Rusting is a chemical process in which iron or steel reacts with oxygen and moisture in the presence of carbon dioxide to form a reddish-brown compound called iron oxide. This process occurs when the iron or steel is exposed to air and moisture for a prolonged period of time.
2. What are the factors that affect the rusting of iron or steel?
Ans. There are several factors that can affect the rusting of iron or steel. These include: - Presence of moisture: Rusting occurs faster in the presence of moisture as it provides the necessary medium for the chemical reaction to take place. - Presence of oxygen: Oxygen is required for rusting to occur. The more oxygen present, the faster the rusting process. - Presence of carbon dioxide: Carbon dioxide in the air can react with water to form carbonic acid, which accelerates the rusting process. - Temperature: Higher temperatures can speed up the rusting process. - Presence of impurities: Impurities in the iron or steel can act as catalysts and accelerate the rusting process.
3. How can rusting be prevented?
Ans. Rusting can be prevented through various methods, including: - Applying a protective coating: Painting or varnishing the iron or steel surface can prevent direct contact with moisture and oxygen. - Galvanization: Coating the iron or steel with a layer of zinc can provide a protective barrier against rust. - Using alloys: Mixing iron or steel with other metals like chromium or nickel can make it more resistant to rusting. - Keeping the surface dry: Preventing the accumulation of moisture on the iron or steel surface can slow down or prevent rusting. - Using sacrificial anodes: Attaching a more easily corroded metal, such as zinc or magnesium, to the iron or steel surface can protect it from rusting.
4. Can rusting occur in the absence of oxygen?
Ans. No, rusting cannot occur in the absence of oxygen. Oxygen is an essential component for the chemical reaction that forms rust. Without oxygen, iron or steel will not undergo the oxidation process that leads to rusting.
5. Does rust affect the structural integrity of iron or steel?
Ans. Yes, rust can significantly affect the structural integrity of iron or steel. As rust forms, it gradually weakens the metal by corroding it. The rusted metal becomes brittle and can easily break or crumble. This can pose a serious safety risk, especially in structures or objects that rely on the strength of iron or steel. Regular maintenance and prevention methods are crucial to ensure the longevity and safety of iron or steel structures.
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