Explain Cathodic protection and alloying method to prevent corrosion with examples? [5 MARKS]
Explain Cathodic protection and alloying method to prevent corrosion with examples? [5 MARKS]
Each point: 2.5 Mark
1. Cathodic protection : The more reactive metal are more corrosion-prone which connect to a bar of another metal (which is less reactive) that is even more prone to corrosion. In this process electron flow from the more reactive metal to the less reactive metal. The metal to be protected becomes the cathode and the more reactive metal becomes the anode. In this way, the two metals form an electrochemical cell and oxidation of the metal is prevented.
For example : The pipelines (iron) under the surface of the earth are protected from corrosion by connecting them to a more reactive metal (Magnesium or Zn) which buried in the earth and connected to the pipelines by a wire.
2. By alloying : It is a very good method of improving the properties of a metal.
For example : Iron is the most widely used metal. But it is never used in its pure state. This is because pure iron is very soft and stretches easily when hot. But, if it is mixed with a small amount of carbon (about 0.05%) it becomes hard and strong. When iron is mixed with nickel and chromium to form stainless steel which is hard and does not rust, i.e. properties of its changes. In fact, the properties of any metal can be changed, if it is mixed with some other substances.
Each point: 2.5 Mark
1. Cathodic protection : The more reactive metal are more corrosion-prone which connect to a bar of another metal (which is less reactive) that is even more prone to corrosion. In this process electron flow from the more reactive metal to the less reactive metal. The metal to be protected becomes the cathode and the more reactive metal becomes the anode. In this way, the two metals form an electrochemical cell and oxidation of the metal is prevented.
For example : The pipelines (iron) under the surface of the earth are protected from corrosion by connecting them to a more reactive metal (Magnesium or Zn) which buried in the earth and connected to the pipelines by a wire.
2. By alloying : It is a very good method of improving the properties of a metal.
For example : Iron is the most widely used metal. But it is never used in its pure state. This is because pure iron is very soft and stretches easily when hot. But, if it is mixed with a small amount of carbon (about 0.05%) it becomes hard and strong. When iron is mixed with nickel and chromium to form stainless steel which is hard and does not rust, i.e. properties of its changes. In fact, the properties of any metal can be changed, if it is mixed with some other substances.
