Cathode protection is one of the effective, well
known, and extensively used methods for prevention of corrosion in concrete
structures in more advanced countries. Due to high cost and long term
monitoring required for this method, it is not very much used in India.
The cathode protection comprises of application of
impressed current, to an electrode laid on the concrete, above steel
reinforcement. This electrode serves as anode and the steel reinforcement,
which is connected to the negative terminal of a DC source acts as a cathode.
In this process, the external anode is subjected to corrode
and the cathode reinforcement is protected against
corrosion and hence the name 'Cathode Protection'.
In this process, the -ve
chloride ions, which are responsible for the damage of the passivating film,
are drawn away from the vicinity of steel towards the anode, where they are
oxidized to form chlorine gas.
The other recent development in corrosion control
methods are Re-alkalization and De-salnation. The re-alkalisation process
allows to make the concrete alskline again and passivate the reinforcement
steel, by electro-chemical method. This brings back the lost alkalinity of
concrete of sufficiently high level to reform and maintain the passive layer on
In the desalination process, the chloride ions are removed
form the concrete, particularly from the vicinity of the steel reinforcement by
certain electrical method to re-establish the passive layer of the steel.
It appears that the application of cathodic
systems for protection of concrete structures, offers some real hope to the
concrete technologist, but the field remains open for the introduction of
innovative methods to overcome problems of both technique and cost.