Question

In the galvanizing process , iron is coated with zinc . The resulting chemical protection is most similar to that provided when :
A.a magnesium bar is connected to an iron pipe
B.an iron can is plated with tin
C.copper pipes are connected using lead solder
D.a copper pipe is covered with epoxy paint

Answer 1

Hint: Galvanization is a method of preventing rusting in metals like iron . It is done by applying a coating of zinc to the iron article so that the iron does not react directly with air and hence rusting does not take place .

Complete answer:
 When iron is coated with zinc the oxidation of zinc takes place and iron is not oxidised as zinc protects it.
-Now this process is possible because zinc is more reactive than iron , this type of protection in which iron is coated with a more reactive element is known as sacrificial protection .
-Now , tin and magnesium both can be used for galvanizing purposes but tin does not provide sacrificial protection because it is less reactive than iron but magnesium does provide sacrificial protection because it is more reactive than iron .
-Therefore when iron is coated with zinc and when a magnesium bar is connected to an iron pipe similar chemical protection is provided .
-The reason why copper pipes are connected using lead solder is that lead is prevented from discharging in the drinking water .
So, The correct answer is (A).

Note:
In the method of sacrificial protection, the metals which are used for protection of iron and steel, that is, zinc or magnesium act as anodes which corrode in the process while the metals which are protected act as cathodes and do not corrode.
That is why these metals are known as sacrificial anodes as they attract the corrosion towards themselves .They must be replaced periodically as they get corroded and are not much effective for a longer period of time.