Environmental Engineering Reference
In-Depth Information
Figure 4.8
Corrosion of a buried pipeline. Arrows show the direction of current flow.
open-circuit potential of anodic reaction, the corrosion stops completely as the
driving force (
E
c
E
A
) becomes zero.
I
applied
is the current requirement for com-
plete protection. However, a current of lower magnitude will provide some
degree of protection. For example, and applied current corresponding to the point
e will bring down the corrosion current from
I
corros
to that corresponding to the
point b.
If polarization is continued beyond the point f, i.e., if the current applied is
Figure 4.9
Polarization diagram illustrating principle of cathodic protection.
