Class 7 Chemistry Physical and Chemical Changes Prevention of rusting of iron

Prevention of rusting of iron

Following methods can be used to prevent corrosion:

  • Galvanisation

Method to protect steel and iron articles from rusting by coating them with a thin layer of zinc.

Fig. Galvanised iron used for fencing

 

  • Alloying

Homogeneous mixture of two or more metals, or a metal and a non-metal to change the properties of the pure state metals and protect them from rust.

  1. For instance, Iron is used widely for different purposes but it is never used in pure state. It is due to the fact that pure iron is very soft and stretches in hot state. But mixing with small amount of carbon (about 0.05%) makes it strong and tough. Mixing nickel and chromium with iron gives stainless steel, which is hard and does not rust.

Fig. Stainless steel

  1. Another vital property of alloy is that electrical conductivity and melting point of an alloy is less than that of pure metals. For instance, brass is an alloy of copper and zinc (Cu and Zn), and bronze is an alloy of copper and tin (Cu and Sn), possessing poor conductivity towards electricity. On the other hand copper in pure state is used for making electrical circuits.

   

Fig. Musical instrument made of Brass (left) and bronze statue (right)

Solder is an alloy of lead and tin (Pb and Sn) possessing low melting point and is used for welding electrical wires together

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