What is Corrosion Video Lecture - NEET

in this video we are going to learn
about corrosion imagine for objects an
aluminium soy and iron now a copper pipe
then a gold ring are left out in the
open for many years which are the four
materials do you think will be in the
best condition when they are
rediscovered pause think and continue
and ready if you think the gold ring is
likely to be in the best condition
you're right
the copper pipe and the iron now will
appear in a worse condition but the
aluminium toy is also preserved very
well most likely the iron now will
appear in the worse condition this is
because of corrosion corrosion is
described as formation of compounds on
the surface of a metal when it is
exposed to air and or water or an
electrolyte like salt water typically
once a metal corrodes it forms compounds
known as oxides or hydrated oxides the
now made of iron rusted this by the way
is the only time you should use the term
rusting all other metals are considered
as having been corroded when they react
with water and/or oxygen it in the air
but why would the nail be more corroded
than the aluminium toy the copper pipe
or the gold ring have you any ideas
pause the video and continue and ready
the reason is the metals all have
different reactivities iron corrodes
faster because it is more reactive than
the copper and the gold but you may be
wondering why didn't the aluminium toy
corrode the fastest the truth is the
aluminium is more reactive than the iron
so it reacts fastest with the oxygen
from the air forming aluminium oxide
aluminium oxide is very unreactive
because once the oxide layer is formed
on the surface it binds very tightly to
the surface of the metal so no cracks
can form and cause further corrosion
here's a challenge how might you use
this idea to protect the iron now the
answer is that by covering a metal like
iron with a
of a more reactive metal like zinc is
that the zinc forms the zinc oxide layer
quickly the iron underneath is protected
this process is called galvanizing and
can last up to a hundred years if you
think on the metal on a bike corrosion
can be prevented by a paint in the frame
a static part or greasing the metal
parts like the chain which moves or by
covering it with a thin layer of a less
reactive metal like tin copper or gold
but that would be very expensive