CATHODIC PROTECTION
When a metal surface is in contact with an electrolyte,
differences in electrical potential develop between
local areas of the surface corresponding to this
respective electrochemical reactivities; a more
reactive (less noble) area is referred to as being
anodic to a less reactive (more noble) cathodic
area.
The
difference in potential between two areas causes
a current to flow from the cathode to the anode
through the metal, and from the anode to the cathode
through the electrolyte to complete the circuit.
When the current enters the electrolyte, metal ions
go into solution, causing corrosion of the anode.
This
corrosion can be prevented if it is connected electrically
by a wire or rod to an e.g. zinc anode, also in
contact with the electrolyte.
