question_answer

What is rusting? How do we prevent it?

Answer:

If we leave a piece of iron in the open for some time, it acquires a coating of brownish substance. This substance is called rust and the process of its formation is called rusting. This is the change that effects iron articles and slowly destroys them. Since iron is used in making bridges, ships, cars, truck bodies and many other articles, the monetary loss due to rusting is huge.

For rusting the presence of both oxygen and water (or water vapour) is essential.

In fact, if the moisture content in air is high which means if it is more humid, rusting becomes faster.

Methods of preventing rust formation: Rusting of an iron object can be prevented or reduced by not allowing air and moisture to come in contact with its surface. Following are the methods of prevention from rusting:

(i) Putting oil or paint over the surface of iron implements.

(ii) Galvanization: In this method, surface of iron is covered with a layer of more active metal like zinc. Zinc metal looses electrons in preference to iron and hence, prevents the rusting of iron.

(iii) By tin-plating.

(iv) Use of anti-rust solutions: Alkaline chromate and alkaline phosphate solutions act as anti-rust solutions. When iron objects are dipped into a boiling and strongly alkaline solution of sodium phosphate, a protective insoluble film of iron phosphate is formed on them. This film protects the article form rusting.