The galvanised articles are prevented from rusting even if the zinc coating is broken .why?
A galvanized substance is that which has been coated with a
layer of zinc to delay corrosion.It does this by the zinc getting
corroded itself,instead of the substance.
The outer layer of zinc of any galvanized material, reacts with
the atmospheric oxygen to form Zinc Oxide (ZnO), which is stronger
than Zinc. Thus, even if the outer layer of zinc undergoes
corrosion, the material is getting coated with a stronger substance
(ZnO), and thus is better able to resist corrosion.