Question

How does the metal activity series relate to corrosion?

Answer 1

Metal activity series is an arrangement of the metals according to their reactive nature. Corrosion means the degradation of the metal due to air and water, in which rusting of iron is an example.

Complete answer: Metal activity series is an arrangement of the metals according to their reactive nature. We know that metals are very reactive in nature, so they easily form compounds with other substances. In the metal activity series, all the metals are arranged from lithium on the top to silver at the bottom, which means that lithium is the most reactive metal while silver is the least reactive metal.
Corrosion means the degradation of the metal due to air and water, in which rusting of iron is an example. So, to prevent the degradation of any metal from air or water, we usually apply a layer of metal that is more reactive than the previous metal or which is above in the metal activity series.
Corrosion means the oxidation of iron, which means there are removal electrons from iron due to air and water. The reaction is given below:
$Fe(s)\to F{{e}^{2+}}(aq)+2{{e}^{-}}$
Now, these ions can react with hydroxide ions to form $Fe{{(OH)}_{2}}$ which on further oxidation and dehydration converts into rust.
So, to stop the rusting iron, we apply a layer of zinc or magnesium because they are more reactive than iron and will corrode first.

Note: The pipelines underground are also made up of iron, so the bags of magnesium scraps are attached at intervals so, that the corrosion of the iron does not take place at a faster rate, the rusting of iron will take place only after the magnesium has been fully corroded.