When two
or more dissimilar metals are immersed in any electrolyte they
exchange their ions
trying to create a balance electrical field. The negative
ions (cathode)
are pulled by the positive (anode) and this movement of the
ions goes
with the lights speed (300.000 Km/sec).
This is to say the
negative ions
are bombing the metals whose atoms have more positive ions
with the result that
these metals deteriorate.
When a 'zinc/aluminium/or
other metal alloy' (called as well 'anode') are
placed close
by, these positive loaded metals
(anodes) pull towards
themselves the
free moving negative ions and thereby protect other metals
from being deteriorated.
More
about Electrolysis
Cathodic Protection
Electrolysis & Protection