HOW DOES RUSTING OF IRON COSTS OUR COUNTRY IN MILLIONS OF
RUPEES EVERY YEAR? FIND OUT. ALSO MENTION THE WAYS BY WHICH WE
CAN PREVENT THIS TREMENDOUS LOSS OF MONEY? (200 WORDS)
Answers
Answer:
Explanation:
Rusting of iron refers to the formation of rust, a mixture of iron oxides, on the surface of iron objects or structures. This rust is formed from a redox reaction between oxygen and iron in an environment containing water (such as air containing high levels of moisture). The rusting of iron is characterized by the formation of a layer of a red, flaky substance that easily crumbles into a powder.
Oxygen is a very good oxidizing agent whereas iron is a reducing agent. Therefore, the iron atom readily gives up electrons when exposed to oxygen. The chemical reaction is given by:
Fe → Fe2+ + 2e–
The oxidation state of iron is further increased by the oxygen atom when water is present.
4Fe2+ + O2 → 4Fe3+ + 2O2-
Now, the following acid-base reactions occur between the iron cations and the water molecules.
Fe2+ + 2H2O ⇌ Fe(OH)2 + 2H+
Fe3+ + 3H2O ⇌ Fe(OH)3 + 3H+
The hydroxides of iron are also formed from the direct reaction between the iron cations and hydroxide ions.
O2 + H2O + 4e– → 4OH–
Fe2+ + 2OH– → Fe(OH)2
Fe3+ + 3OH– → Fe(OH)3
Some alloys of iron are rust-resistant. Examples include stainless steel (which features a layer of chromium(III) oxide) and weathering steel.
COR-TEN steel rusts at a relatively slower rate when compared to normal steel. In this alloy, the rust forms a protective layer on the surface of the alloy, preventing further corrosion.
Galvanization
Galvanization is the process of applying a protective layer of zinc on a metal. It is a very common method of preventing the rusting of iron.
This can be done by dipping the metal to be protected in hot, molten zinc or by the process of electroplating.
Zinc is a relatively cheap metal that sticks to steel easily. It also offers cathodic protection to the iron surface by acting as an anode. The zinc layer is corroded instead of the iron due to this.
The disadvantages of galvanization are that it only provides protection from corrosion for a limited amount of time since the zinc layer is eaten up in the process. It is not very effective in highly corrosive areas (where cadmium coating can be used instead).